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In Java, every variable has a type. You declare a variable by placing the type first, followed by the name of the variable. Here are some examples:

在Java中，每個(gè)變量都有一個(gè)類型。你可以用把類型寫(xiě)在前面，后面緊跟變量名的方式來(lái)聲明變量。下面是一些例子：

double salary;

int vacationDays;

long earthPopulation;

boolean done;

Notice the semicolon at the end of each declaration. The semicolon is necessary because a declaration is a complete Java statement.

注意每一個(gè)聲明后面的分號(hào)。由于每個(gè)聲明都是一條完整的Java語(yǔ)句，所以分號(hào)是必須寫(xiě)的。

A variable name must begin with a letter and must be a sequence of letters or digits. Note that the terms "letter" and "digit" are much broader in Java than in most languages. A letter is defined as 'A'–'Z', 'a'–'z', '_', or any Unicode character that denotes a letter in a language. For example, German users can use umlauts such as '?' in variable names; Greek speakers could use a p. Similarly, digits are '0'–'9' and any Unicode characters that denote a digit in a language. Symbols like '+' or '?' cannot be used inside variable names, nor can spaces. All characters in the name of a variable are significant and case is also significant. The length of a variable name is essentially unlimited.

變量名必須以字母開(kāi)頭的一串字母或數(shù)字序列。注意，Java中所說(shuō)的“字母”和“數(shù)字”比大多數(shù)編程語(yǔ)言要寬泛的多。字母是指'A'–'Z', 'a'–'z', '_',或者任何在某種語(yǔ)言中表示某個(gè)字母的Unicode字符。例如，德國(guó)人可以在變量名中使用元音變音'?'；希臘人可以使用p。類似的，數(shù)字也是'0'–'9'或者任何在某種語(yǔ)言中表示一個(gè)數(shù)位的Unicode字符。諸如'+' or '?'此類的字符也不能被用于變量名，空格也不可以。所有的變量名中的字符乃至大小寫(xiě)都是有意義的。變量名的長(zhǎng)度幾乎是沒(méi)有限制的。

TIP

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If you are really curious as to what Unicode characters are "letters" as far as Java is concerned, you can use the isJavaIdentifierStart and isJavaIdentifierPart methods in the Character class to check.

提示

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如果你真的像關(guān)心Java那樣對(duì)于何種Unicode字符屬于“字母”感到好奇的話，不妨用Character類中的isJavaIdentifierStart和isJavaIdentifierPart方法去檢查。

You also cannot use a Java reserved word for a variable name. (See Appendix A for a list of reserved words.)

你不能用Java保留字作為變量名。

You can have multiple declarations on a single line:

你可以在同一行聲明多個(gè)變量：

int i, j; // both are integers

However, we don't recommend this style. If you declare each variable separately, your programs are easier to read.

但是，我們并不推薦使用這種方式。如果你分別聲明每一個(gè)變量，你的程序可讀性更好。

NOTE

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As you saw, names are case sensitive, for example, hireday and hireDay are two separate names. In general, you should not have two names that only differ in their letter case. However, sometimes it is difficult to come up with a good name for a variable. Many programmers then give the variable the same name of the type, such as

Box box; // ok--Box is the type and box is the variable name

Other programmers prefer to use an "a" prefix for the variable:

Box aBox;

注釋

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如你所見(jiàn)，命名是區(qū)分大小寫(xiě)的，例如，hireday和hireDay是兩個(gè)不同的名字。通常，你不應(yīng)該僅僅通過(guò)大小寫(xiě)來(lái)區(qū)分兩個(gè)命名。但是，有時(shí)候很難給一個(gè)變量起一個(gè)好名字。很多程序員就用與類型名相同的名字來(lái)給變量命名，例如：

Box box; // ok--Box 是個(gè)類型而 box 是變量名

有的程序員喜歡給變量名加上一個(gè)“a”前綴：

Box aBox;

Initializing Variables變量初始化

After you declare a variable, you must explicitly initialize it by means of an assignment statement—you can never use the values of uninitialized variables. For example, the Java compiler flags the following sequence of statements as an error:

聲明變量以后，你必須明確的用一個(gè)賦值語(yǔ)句對(duì)其初始化——你絕不能夠使用一個(gè)沒(méi)有初始化的變量。例如，Java編譯器將會(huì)標(biāo)記如下語(yǔ)句為一個(gè)錯(cuò)誤：

int vacationDays;

System.out.println(vacationDays); // ERROR--variable not initialized

You assign to a previously declared variable by using the variable name on the left, an equal sign (=), and then some Java expression that has an appropriate value on the right.

給變量賦值時(shí)，你可以把先前聲明好的變量名寫(xiě)在左邊，再寫(xiě)一個(gè)等號(hào)(=)，然后右邊緊跟一些Java具有適當(dāng)值的表達(dá)式。

int vacationDays;

vacationDays = 12;

You can both declare and initialize a variable on the same line. For example:

你也可以把變量的聲明和初始化寫(xiě)在一行，例如：

int vacationDays = 12;

Finally, in Java you can put declarations anywhere in your code. For example, the following is valid code in Java:

最后要說(shuō)明的，在Java中，你可以把變量的聲明放在你代碼的任何地方。比如，下面的代碼在Java中是正確的：

double salary = 65000.0;

System.out.println(salary);

int vacationDays = 12; // ok to declare a variable here

In Java, it is considered good style to declare variables as closely as possible to the point where they are first used.

在Java中，一種比較好的方式就是聲明變量以后緊接著指出該變量第一次使用的位置。

C++ NOTE

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C and C++ distinguish between the declaration and definition of variables. For example,

int i = 10;

is a definition, whereas

extern int i;

is a declaration. In Java, no declarations are separate from definitions.

C++ 附注

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C和C++中區(qū)分聲明和定義。例如：

int i = 10;

是一個(gè)定義，而

extern int i;

是一個(gè)聲明。在Java中，沒(méi)有獨(dú)立于定義的聲明。

Constants常量

In Java, you use the keyword final to denote a constant. For example,

在Java中，你可以用關(guān)鍵字final來(lái)指明一個(gè)常量，例如：

public class Constants

{

public static void main(String[] args)

{

final double CM_PER_INCH = 2.54;

double paperWidth = 8.5;

double paperHeight = 11;

System.out.println("Paper size in centimeters: "

+ paperWidth * CM_PER_INCH + " by " + paperHeight * CM_PER_INCH);

}

}

The keyword final indicates that you can assign to the variable once, and then its value is set once and for all. It is customary to name constants in all upper case.

關(guān)鍵字final指出你可以給變量賦值一次，而其值也只能設(shè)置一次。通常習(xí)慣上將常量名全部大寫(xiě)。

It is probably more common in Java to want a constant that is available to multiple methods inside a single class. These are usually called class constants. You set up a class constant with the keywords static final. Here is an example of using a class constant:

在Java中，我們或許更多時(shí)候需要一個(gè)能被一個(gè)類中的多個(gè)方法使用的常量。這種常量被稱之為類常量。類常量用關(guān)鍵字static final來(lái)設(shè)置。下面是一個(gè)使用類常量的例子：

public class Constants2

{

public static void main(String[] args)

{

double paperWidth = 8.5;

double paperHeight = 11;

System.out.println("Paper size in centimeters: "

+ paperWidth * CM_PER_INCH + " by " + paperHeight * CM_PER_INCH);

}

public static final double CM_PER_INCH = 2.54;

}

Note that the definition of the class constant appears outside the main method. Thus, the constant can also be used in other methods of the same class. Furthermore, if (as in our example) the constant is declared public, methods of other classes can also use the constant—in our example, as Constants2.CM_PER_INCH.

注意到對(duì)類常量的定義出現(xiàn)在了主方法的外面。正因?yàn)槿绱耍惓Ａ恳部梢员煌惖钠渌椒ㄔL問(wèn)。此外，如果（如我們的例子）常量被聲明為public，那么其他類的方法也可以使用這個(gè)常量——在我們的例子中，就像Constants2中的CM_PER_INCH一樣。

C++ NOTE

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const is a reserved Java keyword, but it is not currently used for anything. You must use final for a constant.

C++ 注釋

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const是一個(gè)Java預(yù)留的關(guān)鍵字，但是現(xiàn)在不再用于任何場(chǎng)合。你必須使用final來(lái)定義常量。

文章來(lái)源:http://x-spirit.spaces.live.com/Blog/cns!CC0B04AE126337C0!300.entry

Java is a strongly typed language. This means that every variable must have a declared type. There are eight primitive types in Java. Four of them are integer types; two are floating-point number types; one is the character type char, used for code units in the Unicode encoding scheme (see the section on the char type); and one is a boolean type for truth values.

Java是一種強(qiáng)類型語(yǔ)言。這意味著每個(gè)變量必須聲明類型。Java中有八種原始類型。其中4種是整數(shù)類型；兩種是浮點(diǎn)數(shù)類型；一種是字符類型char，適用于Unicode編碼方案中的代碼單元（參見(jiàn)本節(jié)中的char類型小節(jié)）；還有一種是用來(lái)表示真值的布爾類型。

NOTE注釋

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Java has an arbitrary precision arithmetic package. However, "big numbers," as they are called, are Java objects and not a new Java type. You see how to use them later in this chapter.

Java有一個(gè)任意精度的算術(shù)包。顧名思義，“大數(shù)”是一個(gè)Java對(duì)象，而并非新的Java類型。你將在本章后面看到如何使用它們。

Integers整數(shù)

The integer types are for numbers without fractional parts. Negative values are allowed. Java provides the four integer types shown in Table 3-1.

整數(shù)類型是四種無(wú)小數(shù)部分的數(shù)字，允許負(fù)值。Java提供表3-1所示的四種整數(shù)類型。

Table 3-1. Java Integer Types

類型

存儲(chǔ)空間

范圍（閉區(qū)間）

Int

4 字節(jié)

–2,147,483,648 to 2,147,483, 647 (超過(guò)20億)

Short

2字節(jié)

–32,768 to 32,767

Long

8字節(jié)

–9,223,372,036,854,775,808 to 9,223,372,036,854,775,807

Byte

1字節(jié)

–128 to 127

In most situations, the int type is the most practical. If you want to represent the number of inhabitants of our planet, you'll need to resort to a long. The byte and short types are mainly intended for specialized applications, such as low-level file handling, or for large arrays when storage space is at a premium.

大多數(shù)情況下，int類型是最實(shí)用的。如果你想表示我們星球上居民的數(shù)量，你就需要訴諸于long類型。Byte和short類型主要用于一些特殊的應(yīng)用，比如較低級(jí)的文件處理，或者當(dāng)存儲(chǔ)空間非常珍貴的時(shí)候處理大的數(shù)組。

Under Java, the ranges of the integer types do not depend on the machine on which you will be running the Java code. This alleviates a major pain for the programmer who wants to move software from one platform to another, or even between operating systems on the same platform. In contrast, C and C++ programs use the most efficient integer type for each processor. As a result, a C program that runs well on a 32-bit processor may exhibit integer overflow on a 16-bit system. Because Java programs must run with the same results on all machines, the ranges for the various types are fixed.

Long integer numbers have a suffix L (for example, 4000000000L). Hexadecimal numbers have a prefix 0x (for example, 0xCAFE). Octal numbers have a prefix 0. For example, 010 is 8. Naturally, this can be confusing, and we recommend against the use of octal constants.

在Java中，整數(shù)類型的范圍不取決于你運(yùn)行Java代碼的機(jī)器。這避免了將軟件在兩個(gè)平臺(tái)或者在同一平臺(tái)上的兩個(gè)操作系統(tǒng)之間轉(zhuǎn)移而帶來(lái)的主要麻煩。與之相反的是，C和C++程序?qū)γ總€(gè)處理器使用最有效的整數(shù)類型。造成的結(jié)果就是，一個(gè)C程序在一個(gè)32位處理器上運(yùn)行良好而在一個(gè)16位系統(tǒng)中可能表現(xiàn)出整數(shù)溢出。因?yàn)镴ava程序必須保證在所有的機(jī)器上運(yùn)行得到相同的結(jié)果，不同類型的范圍是固定的。長(zhǎng)整型數(shù)字有一個(gè)L后綴（例如4000000000L）。十六位數(shù)字有一個(gè)0x前綴（例如，0xCAFE）。八進(jìn)制數(shù)字有一個(gè)0前綴。例如，010就是8。當(dāng)然，這可能導(dǎo)致混淆，所以我們建議避免使用八進(jìn)制數(shù)。

C++ NOTE C++注釋

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In C and C++, int denotes the integer type that depends on the target machine. On a 16-bit processor, like the 8086, integers are 2 bytes. On a 32-bit processor like the Sun SPARC, they are 4-byte quantities. On an Intel Pentium, the integer type of C and C++ depends on the operating system: for DOS and Windows 3.1, integers are 2 bytes. When 32-bit mode is used for Windows programs, integers are 4 bytes. In Java, the sizes of all numeric types are platform independent.

Note that Java does not have any unsigned types.

在C和C++中，int表示的整數(shù)類型取決于目標(biāo)機(jī)。在16位處理器上，例如8086機(jī)，整數(shù)占用2字節(jié)。在32位處理器，例如Sun公司的SPARC，整數(shù)占用4字節(jié)。在Intel奔騰上，C和C++的整數(shù)類型取決于操作系統(tǒng)：對(duì)于DOS和Windows3.1，整數(shù)是2字節(jié)。當(dāng)Windows程序使用32位模式時(shí)，整數(shù)占用4字節(jié)。在Java中，一切數(shù)字類型的大小都是平臺(tái)無(wú)關(guān)的。注意，Java沒(méi)有任何無(wú)符號(hào)類型。

Floating-Point Types浮點(diǎn)類型

The floating-point types denote numbers with fractional parts. The two floating-point types are shown in Table 3-2.

浮點(diǎn)類型表示的數(shù)字含有小數(shù)部分。表3-2顯示了兩種浮點(diǎn)類型。

Table 3-2. Floating-Point Types

類型

存儲(chǔ)空間

范圍

float

4字節(jié)

大約 ±3.40282347E+38F (6–7 個(gè)有效十進(jìn)制位)

double

8字節(jié)

大約 ±1.79769313486231570E+308 (15個(gè)有效十進(jìn)制位)

The name double refers to the fact that these numbers have twice the precision of the float type. (Some people call these double-precision numbers.) Here, the type to choose in most applications is double. The limited precision of float is simply not sufficient for many situations. Seven significant (decimal) digits may be enough to precisely express your annual salary in dollars and cents, but it won't be enough for your company president's salary. The only reasons to use float are in the rare situations in which the slightly faster processing of single-precision numbers is important or when you need to store a large number of them.

Numbers of type float have a suffix F (for example, 3.402F). Floating-point numbers without an F suffix (such as 3.402) are always considered to be of type double. You can optionally supply the D suffix (for example, 3.402D).

Double這個(gè)名字說(shuō)明該類型具有兩倍于float類型的精度。（有人將之稱為雙精度數(shù)字。）這里，大多數(shù)應(yīng)用程序選擇double類型。Float類型有限的精度對(duì)于許多情況都是不足的。七個(gè)有效的十進(jìn)制位也許用來(lái)以美元和美分的單位表示你的年薪還是足夠的，但是用來(lái)表示你公司老總的薪水就顯得不夠了。僅當(dāng)極少數(shù)需要對(duì)單精度數(shù)字進(jìn)行敏捷的處理或者需要存儲(chǔ)大量單精度數(shù)字的時(shí)候，才有理由使用float類型。

As of JDK 5.0, you can specify floating-point numbers in hexadecimal. For example, 0.125 is the same as 0x1.0p-3. In hexadecimal notation, you use a p, not an e, to denote the exponent.

從JDK5.0起，你可以指定十六進(jìn)制的浮點(diǎn)數(shù)字。例如，0.125就等同于0x1.0p-3。在十六進(jìn)制符號(hào)中，采用p而非e來(lái)表示指數(shù)。

All floating-point computations follow the IEEE 754 specification. In particular, there are three special floating-point values:

positive infinity

negative infinity

NaN (not a number)

to denote overflows and errors. For example, the result of dividing a positive number by 0 is positive infinity. Computing 0/0 or the square root of a negative number yields NaN.

所有浮點(diǎn)計(jì)算遵循IEEE 754規(guī)范。特別的，有三種特殊的浮點(diǎn)值：

positive infinity正無(wú)窮

negative infinity負(fù)無(wú)窮

NaN (非數(shù)字)

來(lái)表示溢出和錯(cuò)誤。例如，將一個(gè)正數(shù)除以0得到的結(jié)果就是正無(wú)窮。0/0或者負(fù)數(shù)的平方根就是NaN。

NOTE注釋

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The constants Double.POSITIVE_INFINITY, Double.NEGATIVE_INFINITY, and Double.NaN (as well as corresponding Float constants) represent these special values, but they are rarely used in practice. In particular, you cannot test

if (x == Double.NaN) // is never true

to check whether a particular result equals Double.NaN. All "not a number" values are considered distinct. However, you can use the Double.isNaN method:

if (Double.isNaN(x)) // check whether x is "not a number"

常量Double.POSITIVE_INFINITY、Double.NEGATIVE_INFINITY、Double.NaN（以及相應(yīng)的Float常量）表示以上特殊值。但它們?cè)趯?shí)際應(yīng)用中非常少用。特別的，你無(wú)法測(cè)試

if(x==Double.NaN)//永不為真

來(lái)檢查實(shí)際結(jié)果是否等于Double.NaN。所有“非數(shù)字”值被歸為獨(dú)特的。但是你可以使用Double.isNaN方法。

if (Double.isNaN(x)) // 檢測(cè)x是否是“非數(shù)字”。

CAUTION注意

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Floating-point numbers are not suitable for financial calculation in which roundoff errors cannot be tolerated. For example, the command System.out.println(2.0 - 1.1) prints 0.8999999999999999, not 0.9 as you would expect. Such roundoff errors are caused by the fact that floating-point numbers are represented in the binary number system. There is no precise binary representation of the fraction 1/10, just as there is no accurate representation of the fraction 1/3 in the decimal system. If you need precise numerical computations without roundoff errors, use the BigDecimal class, which is introduced later in this chapter.

浮點(diǎn)數(shù)字在不能容忍循環(huán)錯(cuò)誤的財(cái)政計(jì)算中是不合適的。例如，System.out.println(2.0 - 1.1) 命令打印出 0.8999999999999999, 而非你期望得到的0.9。這種循環(huán)錯(cuò)誤是由于在二進(jìn)制系統(tǒng)中表示浮點(diǎn)數(shù)而引起的。對(duì)于分?jǐn)?shù)1/10沒(méi)有精確的二進(jìn)制表示，正如對(duì)于分?jǐn)?shù)1/3沒(méi)有精確的十進(jìn)制表示一樣。如果你需要沒(méi)有循環(huán)錯(cuò)誤的精確數(shù)值計(jì)算，請(qǐng)使用BigDecimal類，這將在本章稍后介紹。

The char Type char類型

To understand the char type, you have to know about the Unicode encoding scheme. Unicode was invented to overcome the limitations of traditional character encoding schemes. Before Unicode, there were many different standards: ASCII in the United States, ISO 8859-1 for Western European languages, KOI-8 for Russian, GB18030 and BIG-5 for Chinese, and so on. This causes two problems. A particular code value corresponds to different letters in the various encoding schemes. Moreover, the encodings for languages with large character sets have variable length: some common characters are encoded as single bytes, others require two or more bytes.

要理解char類型，你需要了解Unicode編碼規(guī)則。Unicode是為克服傳統(tǒng)字符編碼規(guī)則的局限性而發(fā)明的。在Unicode之前，有許多標(biāo)準(zhǔn)：美國(guó)的ASCII、西歐語(yǔ)言的ISO 8859-1、俄語(yǔ)使用的KOI-8、中文使用的GB18030 和 BIG-5等等。這造成了兩個(gè)問(wèn)題。一個(gè)特定的碼值在不同的編碼規(guī)則中對(duì)應(yīng)于不同的字母。此外，大字符集的語(yǔ)言使用的編碼具有可變的長(zhǎng)度：一些普通的字符以單字節(jié)編碼，而其余的需要兩個(gè)或更多字節(jié)。

Unicode was designed to solve these problems. When the unification effort started in the 1980s, a fixed 2-byte width code was more than sufficient to encode all characters used in all languages in the world, with room to spare for future expansion—or so everyone thought at the time. In 1991, Unicode 1.0 was released, using slightly less than half of the available 65,536 code values. Java was designed from the ground up to use 16-bit Unicode characters, which was a major advance over other programming languages that used 8-bit characters.

Unicode的初衷就是解決這個(gè)問(wèn)題。在統(tǒng)一化進(jìn)程始于20世紀(jì)80年代的時(shí)候，一個(gè)定長(zhǎng)的兩字節(jié)碼已經(jīng)足夠?qū)κ澜缟纤姓Z(yǔ)言中的所有字符進(jìn)行編碼，剩下的空間還可以用于將來(lái)的擴(kuò)展——大概當(dāng)初每個(gè)人都是這樣認(rèn)為的。1991年，Unicode 1.0誕生了，僅使用了全部可用65536個(gè)碼值中的一半。Java被設(shè)計(jì)為完全采用16位Unicode字符，這是Java優(yōu)于其他采用8位字符的一個(gè)主要優(yōu)點(diǎn)。

Unfortunately, over time, the inevitable happened. Unicode grew beyond 65,536 characters, primarily due to the addition of a very large set of ideographs used for Chinese, Japanese, and Korean. Now, the 16-bit char type is insufficient to describe all Unicode characters.

We need a bit of terminology to explain how this problem is resolved in Java, beginning with JDK 5.0. A code point is a code value that is associated with a character in an encoding scheme. In the Unicode standard, code points are written in hexadecimal and prefixed with U+, such as U+0041 for the code point of the letter A. Unicode has code points that are grouped into 17 code planes. The first code plane, called the basic multilingual plane, consists of the "classic" Unicode characters with code points U+0000 to U+FFFF. Sixteen additional planes, with code points U+10000 to U+10FFFF, hold the supplementary characters.

不幸的是，隨著時(shí)間的過(guò)去，不可避免的事情發(fā)生了。Unicode超過(guò)了65535個(gè)字符，主要是由于像中文、日文、韓文這樣的大量的象形文字的加入而造成的。現(xiàn)在，16位char類型已經(jīng)不足以描述所有Unicode字符。

我們需要使用一點(diǎn)術(shù)語(yǔ)來(lái)解釋這個(gè)問(wèn)題在Java中，從JDK5.0開(kāi)始是如何得以解決的。一個(gè)代碼點(diǎn)就是一個(gè)編碼規(guī)則中與一個(gè)字符相關(guān)聯(lián)的碼值。在Unicode標(biāo)準(zhǔn)中，代碼點(diǎn)是用16進(jìn)制寫(xiě)成，加上U+前綴，例如U+0041就是字母A的代碼點(diǎn)。Unicode的代碼點(diǎn)被分成17個(gè)代碼組。第一個(gè)代碼組叫做基本多語(yǔ)言組，是由采用U+0000至U+FFFF代碼點(diǎn)的“經(jīng)典”Unicode字符組成。額外的16個(gè)代碼組，代碼點(diǎn)從U+10000至U+10FFFF，保存輔助字符。

The UTF-16 encoding is a method of representing all Unicode code points in a variable length code. The characters in the basic multilingual plane are represented as 16-bit values, called code units. The supplementary characters are encoded as consecutive pairs of code units. Each of the values in such an encoding pair falls into an unused 2048-byte range of the basic multilingual plane, called the surrogates area (U+D800 to U+DBFF for the first code unit, U+DC00 to U+DFFF for the second code unit).This is rather clever, because you can immediately tell whether a code unit encodes a single character or whether it is the first or second part of a supplementary character. For example, the mathematical symbol for the set of integers has code point U+1D56B and is encoded by the two code units U+D835 and U+DD6B. (See http://en.wikipedia.org/wiki/UTF-16 for a description of the encoding algorithm.)

UTF-16編碼是一種以變長(zhǎng)編碼表示所有Unicode代碼點(diǎn)的方法。基本多語(yǔ)言組中的字符以16位值表示，叫做代碼單元。輔助字符以連續(xù)的代碼單元對(duì)編碼。這樣一個(gè)編碼對(duì)中的每個(gè)值就屬于一個(gè)未占用的2048字節(jié)的基本多語(yǔ)言組范圍，稱作代理區(qū)域（U+D800至U+DBFF 表示第一個(gè)代碼單元, U+DC00至U+DFFF表示第二個(gè)代碼單元）。這是相當(dāng)明智的，因?yàn)槟憧梢粤⒓凑f(shuō)出一個(gè)代碼單元是否對(duì)一個(gè)單字符進(jìn)行編碼或者它是輔助字符的第一部分還是第二部分。例如，整數(shù)集的算術(shù)符號(hào)的代碼點(diǎn)為U+1D56B，它是由兩個(gè)代碼單元U+D835和U+DD6B編碼而成。（參見(jiàn)http://en.wikipedia.org/wiki/UTF-16獲得有關(guān)編碼算法的描述）

In Java, the char type describes a code unit in the UTF-16 encoding.

Our strong recommendation is not to use the char type in your programs unless you are actually manipulating UTF-16 code units. You are almost always better off treating strings as abstract data types.

Java中，char類型描述UTF-16編碼中的一個(gè)代碼單元。

我們強(qiáng)烈建議在程序中避免使用char類型，除非你對(duì)UTF-16代碼單元十分熟練。你幾乎總是將字符串視為抽象數(shù)據(jù)類型即可。

Having said that, there will be some cases when you will encounter char values. Most commonly, these will be character constants. For example, 'A' is a character constant with value 65. It is different from "A", a string containing a single character. Unicode code units can be expressed as hexadecimal values that run from \u0000 to \uFFFF. For example, \u2122 is the trademark symbol (?) and \u03C0 is the Greek letter pi (p).

盡管如上所述，但是有時(shí)候你也會(huì)遇到char值。最常見(jiàn)的就是字符常量。例如，‘A’是一個(gè)值為65的字符常量。它與“A”這個(gè)僅包含一個(gè)字符的字符串不同。Unicode代碼單元可被表示成從\u0000到\uFFFF的十六進(jìn)制值。例如，\u2122是商標(biāo)符號(hào)(?) 而 \u03C0 是希臘字母 (p).

Besides the \u escape sequences that indicate the encoding of Unicode code units, there are several escape sequences for special characters, as shown in Table 3-3. You can use these escape sequences inside quoted character constants and strings, such as '\u2122' or "Hello\n". The \u escape sequence (but none of the other escape sequences) can even be used outside quoted character constants and strings. For example,

public static void main(String\5B\5D args)

除了用\u轉(zhuǎn)義符來(lái)表示Unicode代碼單元的編碼，還有一些特殊的轉(zhuǎn)義符來(lái)表示特殊字符，如表3-3所示。你可以在用引號(hào)引起來(lái)的字符常量和字符串中使用這些轉(zhuǎn)義符，例如'\u2122'或"Hello\n"。\u轉(zhuǎn)義符（但其他轉(zhuǎn)義符除外）甚至可以在引號(hào)引起來(lái)的字符常量和字符串外使用。例如：public static void main(String\5B\5D args)

Table 3-3. Escape Sequences for Special Characters

Escape Sequence

Name

Unicode Value

\b

退格

\u0008

\t

Tab

\u0009

\n

換行

\u000a

\r

回車

\u000d

\"

雙引號(hào)

\u0022

\'

單引號(hào)

\u0027

\\

反斜線

\u005c

is perfectly legal—\u005B and \u005D are the UTF-16 encodings of the Unicode code points for [ and ].

是完全合法的——\u005B和\u005D 是“[”和“]”的Unicode代碼點(diǎn)的UTF-16編碼。

NOTE注釋

?

Although you can use any Unicode character in a Java application or applet, whether you can actually see it displayed depends on your browser (for applets) and (ultimately) on your operating system for both.

盡管你可以在任何Java程序和Applet中使用Unicode字符，但實(shí)際上你能否看到這些字符還要取決于你的瀏覽器（對(duì)Applet而言）和你的操作系統(tǒng)（這是最基本的）。

The boolean Type boolean類型（也作布爾類型）

The boolean type has two values, false and true. It is used for evaluating logical conditions. You cannot convert between integers and boolean values.

boolean類型有兩個(gè)值，false和true。這是用來(lái)判斷邏輯條件的。你不能在整型和布爾型之間進(jìn)行轉(zhuǎn)換。

C++ NOTE C++注釋

?

In C++, numbers and even pointers can be used in place of boolean values. The value 0 is equivalent to the bool value false, and a non-zero value is equivalent to true. This is not the case in Java. Thus, Java programmers are shielded from accidents such as

if (x = 0) // oops...meant x == 0

In C++, this test compiles and runs, always evaluating to false. In Java, the test does not compile because the integer expression x = 0 cannot be converted to a boolean value.

在C++中，數(shù)字乃至小數(shù)點(diǎn)都被用于替代布爾值。0值就相當(dāng)于布爾值false而非0值相當(dāng)于true。Java中并非如此。因此Java程序員不會(huì)遇到下面的情況：

if (x = 0) // 哇。。。意味著x==0

C++中，這個(gè)測(cè)試可以編譯并運(yùn)行，并且總是判斷為false。在Java中，這個(gè)測(cè)試無(wú)法編譯，因?yàn)檎捅磉_(dá)式x=0不能被轉(zhuǎn)換為布爾值。

文章來(lái)源:http://x-spirit.spaces.live.com/Blog/cns!CC0B04AE126337C0!289.entry

Comments in Java, like comments in most programming languages, do not show up in the executable program. Thus, you can add as many comments as needed without fear of bloating the code. Java has three ways of marking comments. The most common method is a //. You use this for a comment that will run from the // to the end of the line.

Java中的注釋，和大多數(shù)編程語(yǔ)言中的注釋一樣，在可執(zhí)行程序中不會(huì)顯示。因此，你可以根據(jù)需要任意添加注釋而不必?fù)?dān)心導(dǎo)致代碼膨脹。Java有三種注釋方法。最普通的是用一個(gè)//符號(hào)。用這個(gè)符號(hào)來(lái)注釋從//開(kāi)始到一行結(jié)尾的內(nèi)容。

System.out.println("We will not use 'Hello, World!'"); // is this too cute?

When longer comments are needed, you can mark each line with a //. Or you can use the /* and */ comment delimiters that let you block off a longer comment. This is shown in Example 3-1.

當(dāng)需要更長(zhǎng)的注釋的時(shí)候，你可以用//來(lái)注釋每一行。或者你也可以使用/*和*/這兩個(gè)注釋定界符來(lái)隔離一個(gè)較長(zhǎng)的注釋。如例子3-1所示

Example 3-1. FirstSample.java

1. /*

2. This is the first sample program in Core Java Chapter 3

3. Copyright (C) 1997 Cay Horstmann and Gary Cornell

4. */

5.

6. public class FirstSample

7. {

8.????? public static void main(String[] args)

9.????? {

10.??????????? System.out.println("We will not use 'Hello, World!'");

11.???? }

12. }

Finally, a third kind of comment can be used to generate documentation automatically. This comment uses a /** to start and a */ to end. For more on this type of comment and on automatic documentation generation, see Chapter 4.

最后，第三種注釋用于自動(dòng)生成文檔。該注釋以/**開(kāi)始以*/結(jié)束。有關(guān)這種注釋和自動(dòng)生成文檔的更多內(nèi)容，請(qǐng)見(jiàn)第四章。

CAUTION注意

?

/* */ comments do not nest in Java. That is, you cannot deactivate code simply by surrounding it with /* and */ because the code that you want to deactivate might itself contain a */ delimiter.

/* */注釋在Java中是不可嵌套的。也就是說(shuō)，當(dāng)你想要注釋掉一段代碼的時(shí)候，你不能簡(jiǎn)單的使用/*和*/，因?yàn)槟阆胱⑨尩舻拇a可能就含有一個(gè)*/定界符。

文章來(lái)源:http://x-spirit.spaces.live.com/Blog/cns!CC0B04AE126337C0!287.entry

Let's look more closely at about the simplest Java program you can have—one that simply prints a message to the console window:

讓我們更進(jìn)一步來(lái)看一個(gè)最簡(jiǎn)單的向控制臺(tái)窗口輸出信息的Java程序。

?

public class FirstSample
{
???? ?public static void main(String[] args)
????? {
??????????? System.out.println("We will not use 'Hello, World!'");?
??????}
}

It is worth spending all the time that you need to become comfortable with the framework of this sample; the pieces will recur in all applications. First and foremost, Java is case sensitive. If you made any mistakes in capitalization (such as typing Main instead of main), the program will not run.

你需要花費(fèi)來(lái)熟悉這個(gè)例子的框架，這是值得的，因?yàn)檫@個(gè)框架將在所有應(yīng)用程序中重現(xiàn)。首先，Java是大小寫(xiě)敏感的。如果你在大小寫(xiě)上犯了錯(cuò)誤（例如把Main寫(xiě)成main），程序就不會(huì)運(yùn)行。

Now let's look at this source code line by line. The keyword public is called an access modifier; these modifiers control the level of access other parts of a program have to this code. We have more to say about access modifiers in Chapter 5. The keyword class reminds you that everything in a Java program lives inside a class. Although we spend a lot more time on classes in the next chapter, for now think of a class as a container for the program logic that defines the behavior of an application. As mentioned in Chapter 1, classes are the building blocks with which all Java applications and applets are built. Everything in a Java program must be inside a class.

現(xiàn)在讓我們一行行地來(lái)閱讀這段代碼。關(guān)鍵字public被稱作訪問(wèn)修飾符；這些修飾符控制著這段代碼對(duì)一個(gè)程序其他部分的訪問(wèn)權(quán)限。在第五章中我們將對(duì)訪問(wèn)修飾符做更多討論。關(guān)鍵字class說(shuō)明Java程序中的一切都是存在于類當(dāng)中。盡管在下一章中我們將花費(fèi)更多時(shí)間來(lái)講述類，但現(xiàn)在我們不妨把類想像成一個(gè)承載描述應(yīng)用行為的程序邏輯的容器。正如在第一章中提到的，類是一切Java應(yīng)用程序和applet的構(gòu)建模塊。Java程序中的一切必須存在于類中。

Following the keyword class is the name of the class. The rules for class names in Java are quite generous. Names must begin with a letter, and after that, they can have any combination of letters and digits. The length is essentially unlimited. You cannot use a Java reserved word (such as public or class) for a class name. (See Appendix A for a list of reserved words.)

關(guān)鍵字class后面的就是類名。Java當(dāng)中類的命名規(guī)則是相當(dāng)寬松的。類名必須以字母開(kāi)始，其后可以是任意字母和數(shù)字的組合。類名的長(zhǎng)度基本上是無(wú)限的。你不可以使用Java保留字來(lái)作為類名。（保留字列表請(qǐng)參見(jiàn)附錄A）

The standard naming convention (which we follow in the name FirstSample) is that class names are nouns that start with an uppercase letter. If a name consists of multiple words, use an initial uppercase letter in each of the words. (This use of uppercase letters in the middle of a word is sometimes called "camel case" or, self-referentially, "CamelCase.")

標(biāo)準(zhǔn)的命名規(guī)則是類名需是以一個(gè)大寫(xiě)字母開(kāi)頭的名詞（如FirstSample這個(gè)名字中遵循的規(guī)則）。如果一個(gè)類名以多個(gè)單詞組成，則每個(gè)單詞使用首字母規(guī)則。（這種在一個(gè)詞中間使用大寫(xiě)字母的用法有時(shí)又叫做“camel case”，或者形象的寫(xiě)作“CamelCase”）

You need to make the file name for the source code the same as the name of the public class, with the extension .java appended. Thus, you must store this code in a file called FirstSample.java. (Again, case is important—don't use firstsample.java.)

你需要使文件名和public類的名字相同，后面加上.java擴(kuò)展名。因此，你需要將以上代碼存儲(chǔ)到一個(gè)文件名為FirstSample.java的文件中。（再次說(shuō)明，大小寫(xiě)很重要，不要寫(xiě)成firstsimple.java）

If you have named the file correctly and not made any typos in the source code, then when you compile this source code, you end up with a file containing the bytecodes for this class. The Java compiler automatically names the bytecode file FirstSample.class and stores it in the same directory as the source file. Finally, launch the program by issuing the command:

如果你正確給文件命名并且沒(méi)有在源代碼中寫(xiě)入任何打字稿，那么當(dāng)你編譯這個(gè)源文件時(shí)，你將得到一個(gè)屬于這個(gè)類的包含字節(jié)碼的文件。Java編譯器會(huì)自動(dòng)把字節(jié)碼文件命名為FirstSimple.class并將其存儲(chǔ)在Java源文件的同一目錄下。最后用如下命令來(lái)啟動(dòng)程序：

java FirstSample

(Remember to leave off the .class extension.) When the program executes, it simply displays the string We will not use 'Hello, World'! on the console.

（切記去掉.class擴(kuò)展名）程序執(zhí)行時(shí)，將在控制臺(tái)簡(jiǎn)單輸出一個(gè)字符串：We will not use ‘Hello,World’!

When you use

當(dāng)你用

java?ClassName

to run a compiled program, the Java virtual machine always starts execution with the code in the main method in the class you indicate. Thus, you must have a main method in the source file for your class for your code to execute. You can, of course, add your own methods to a class and call them from the main method. (We cover writing your own methods in the next chapter.)

來(lái)運(yùn)行一個(gè)已經(jīng)編譯的程序時(shí)，Java虛擬機(jī)總是從你指定的類當(dāng)中的main方法開(kāi)始執(zhí)行。當(dāng)然你也可以在一個(gè)類中添加你自己的方法，并將之成為是main方法。（我們將在下一章中討論編寫(xiě)自定義方法。）

NOTE

注意

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According to the Java Language Specification, the main method must be declared public. (The Java Language Specification is the official document that describes the Java language. You can view or download it from http://java.sun.com/docs/books/jls.) However, several versions of the Java launcher were willing to execute Java programs even when the main method was not public. A programmer filed a bug report. To see it, visit the site http://bugs.sun.com/bugdatabase/index.jsp and enter the bug identification number 4252539. However, that bug was marked as "closed, will not be fixed." A Sun engineer added an explanation that the Java Virtual Machine Specification (at http://java.sun.com/docs/books/vmspec) does not mandate that main is public and that "fixing it will cause potential troubles." Fortunately, sanity finally prevailed. The Java launcher in JDK 1.4 and beyond enforces that the main method is public.

根據(jù)Java語(yǔ)言規(guī)范，main方法必須被聲明為public。（Java語(yǔ)言規(guī)范是描述Java語(yǔ)言的官方文檔。你可以從http://java.sun.com/docs/books/jls下載并查看）然而，有些版本的Java啟動(dòng)器在main方法不是public的時(shí)候也會(huì)執(zhí)行Java程序。一個(gè)程序員提交了一個(gè)bug報(bào)告。請(qǐng)?jiān)L問(wèn)站點(diǎn)http://bugs.sun.com/bugdatabase/index.jsp 并輸入bug標(biāo)識(shí)號(hào)4252539來(lái)查看這個(gè)報(bào)告。然而這個(gè)bug被標(biāo)記為“關(guān)閉，將不予修正”。一個(gè)Sun的工程師添加了一條解釋，即Java虛擬機(jī)規(guī)范（http://java.sun.com/docs/books/vmspec）不要求main方法為public，并且“修正這個(gè)問(wèn)題將導(dǎo)致潛在的麻煩.”幸運(yùn)的是，心智健全最終獲勝。JDK1.4及以上版本的Java啟動(dòng)器強(qiáng)制main方法為public。

There are a couple of interesting aspects about this story. On the one hand, it is frustrating to have quality assurance engineers, who are often overworked and not always experts in the fine points of Java, make questionable decisions about bug reports. On the other hand, it is remarkable that Sun puts the bug reports and their resolutions onto the Web, for anyone to scrutinize. The "bug parade" is a very useful resource for programmers. You can even "vote" for your favorite bug. Bugs with lots of votes have a high chance of being fixed in the next JDK release.

關(guān)于這個(gè)故事有兩個(gè)有趣的方面。一方面，讓那些經(jīng)常過(guò)勞工作的且不專于Java的細(xì)琢的質(zhì)量保證工程師對(duì)bug報(bào)告做出充滿問(wèn)題的決議是一件讓人沮喪的事情。另一方面，值得注意的是Sun公司將bug報(bào)告和他們的決議放在網(wǎng)上，供大家細(xì)察。Bug檢閱對(duì)程序員來(lái)說(shuō)是一個(gè)很有用處的資源。你甚至可以為你最青睞的bug投票。那些票數(shù)最高的bug將會(huì)有很大的幾率在下一版的JDK中被修復(fù)。

Notice the braces { } in the source code. In Java, as in C/C++, braces delineate the parts (usually called blocks) in your program. In Java, the code for any method must be started by an opening brace { and ended by a closing brace }.

注意程序中的括號(hào){ }。和在C++中一樣，在Java中，括號(hào)劃分出程序中的各個(gè)部分（通常叫做程序塊或代碼塊）。在Java中，任何方法的代碼都必須以開(kāi)括號(hào){開(kāi)始，以閉括號(hào)}結(jié)束。

Brace styles have inspired an inordinate amount of useless controversy. We use a style that lines up matching braces. Because whitespace is irrelevant to the Java compiler, you can use whatever brace style you like. We will have more to say about the use of braces when we talk about the various kinds of loops.

括號(hào)的使用風(fēng)格引發(fā)了大量混亂的無(wú)用爭(zhēng)論。我們使用一種風(fēng)格將匹配括號(hào)排隊(duì)。因?yàn)榭崭駥?duì)Java編譯器而言無(wú)關(guān)，你可以使用任何你喜歡的括號(hào)風(fēng)格。我們將會(huì)在講述各種循環(huán)的時(shí)候?qū)ㄌ?hào)的使用做更多的討論。

For now, don't worry about the keywords static void—just think of them as part of what you need to get a Java program to compile. By the end of Chapter 4, you will understand this incantation completely. The point to remember for now is that every Java application must have a main method that is declared in the following way:

現(xiàn)在，暫時(shí)不關(guān)注關(guān)鍵字static void，就把他們看作是你要編譯一個(gè)Java程序所必須的。在第四章最后，你將完全理解這個(gè)咒語(yǔ)。現(xiàn)在要記住的是每個(gè)Java應(yīng)用程序必須有一個(gè)像下面這樣定義的main方法：

public class?ClassName
{
???? public static void main(String[] args)
???? {
?????????? program?statements
???? }
}

C++ NOTE C++注釋

?

As a C++ programmer, you know what a class is. Java classes are similar to C++ classes, but there are a few differences that can trap you. For example, in Java all functions are methods of some class. (The standard terminology refers to them as methods, not member functions.) Thus, in Java you must have a shell class for the main method. You may also be familiar with the idea of static member functions in C++. These are member functions defined inside a class that do not operate on objects. The main method in Java is always static. Finally, as in C/C++, the void keyword indicates that this method does not return a value. Unlike C/C++, the main method does not return an "exit code" to the operating system. If the main method exits normally, the Java program has the exit code 0, indicating successful completion. To terminate the program with a different exit code, use the System.exit method.

作為C++程序員，你知道類是什么。Java類和C++中的類相似。但是也有一些不同會(huì)使你陷入其中。例如，在Java中，所有的函數(shù)都是某個(gè)類的方法。（他們的標(biāo)準(zhǔn)術(shù)語(yǔ)叫做方法，而非成員函數(shù)。）因此，在Java中，你必須給main方法一個(gè)外殼類。你或許對(duì)C++中的靜態(tài)成員函數(shù)也很熟悉。這是一些定義在類中但不對(duì)對(duì)象進(jìn)行操作的成員函數(shù)。Java中的main方法總是靜態(tài)的。最后，和在C++中一樣，void關(guān)鍵字說(shuō)明該方法不返回值。與C/C++不同的是，在C/C++中，main方法不會(huì)向操作系統(tǒng)返回一個(gè)“退出碼”。而在Java中，如果main方法正常退出，Java程序?qū)⒎祷匾粋€(gè)退出碼0，以表示成功完成。要以不同的退出碼終止程序，請(qǐng)使用System.exit()方法。

Next, turn your attention to this fragment.

下面，請(qǐng)注意以下這個(gè)片段：

{

???? System.out.println("We will not use 'Hello, World!'");

}

Braces mark the beginning and end of the body of the method. This method has only one statement in it. As with most programming languages, you can think of Java statements as being the sentences of the language. In Java, every statement must end with a semicolon. In particular, carriage returns do not mark the end of a statement, so statements can span multiple lines if need be.

括號(hào)將方法體的開(kāi)始和結(jié)束標(biāo)記出來(lái)。方法中只有一個(gè)句子。和大多數(shù)編程語(yǔ)言一樣，你可以認(rèn)為Java語(yǔ)句就是一個(gè)語(yǔ)言的句子。在Java中，每個(gè)句子必須以分號(hào)結(jié)束。特別要指出的是，回車并不表示語(yǔ)句的結(jié)束，所以在需要的情況下語(yǔ)句可以跨越多行。

The body of the main method contains a statement that outputs a single line of text to the console.

main方法的方法體包含一條向控制臺(tái)輸出單行文本的語(yǔ)句。

Here, we are using the System.out object and calling its println method. Notice the periods used to invoke a method. Java uses the general syntax

這里，我們使用了System.out對(duì)象和它的println方法。注意用于調(diào)用方法的句點(diǎn)。Java使用一般語(yǔ)法：

object.method(parameters)

for its equivalent of function calls.

來(lái)進(jìn)行函數(shù)調(diào)用。

In this case, we are calling the println method and passing it a string parameter. The method displays the string parameter on the console. It then terminates the output line so that each call to println displays its output on a new line. Notice that Java, like C/C++, uses double quotes to delimit strings. (You can find more information about strings later in this chapter.)

此時(shí)，我們調(diào)用println方法并傳一個(gè)字符串參數(shù)給它。這個(gè)方法將該字符串參數(shù)顯示在控制臺(tái)中。之后就結(jié)束該輸出行，因此，每個(gè)println調(diào)用都可以將其輸出寫(xiě)入一個(gè)新行。注意到Java和C++一樣，也使用雙引號(hào)來(lái)劃分字符串。（本章稍后將詳細(xì)討論字符串）

Methods in Java, like functions in any programming language, can use zero, one, or more parameters (some programmers call them arguments). Even if a method takes no parameters, you must still use empty parentheses. For example, a variant of the println method with no parameters just prints a blank line. You invoke it with the call

Java中的方法，像任何編程語(yǔ)言中的一樣，可以使用零個(gè)一個(gè)或者更多參數(shù)（一些程序員習(xí)慣稱之為變量）。即使有些方法沒(méi)有參數(shù)，你也必須使用空?qǐng)A括號(hào)。例如，不同的無(wú)參println方法只輸出一個(gè)空行。你可以通過(guò)以下方法調(diào)用它：

System.out.println();

NOTE 注釋

?

System.out also has a print method that doesn't add a new line character to the output. For example, System.out.print("Hello") prints "Hello" without a new line. The next output appears immediately after the "o".

System.out 也有一個(gè)不換行的print方法，例如System.out.print(“Hello”)就可以輸出”Hello”而不換行。下個(gè)輸出將緊跟在“o”的后面。

文章來(lái)源:http://x-spirit.spaces.live.com/Blog/cns!CC0B04AE126337C0!286.entry

終于決定好好的學(xué)習(xí)Core Java了。

我的Core Java學(xué)習(xí)筆記基本上是自己把原文翻譯一遍，然后對(duì)部分有價(jià)值的代碼進(jìn)行一些討論。

學(xué)習(xí)筆記僅從最重要的部分開(kāi)始。前兩章暫不涉及。

原版書(shū)籍來(lái)源于Flyheart提供的電子書(shū)。本學(xué)習(xí)筆記連載的內(nèi)容僅供自學(xué)之用，嚴(yán)禁用于任何商業(yè)用途，由此引起的任何后果本人概不負(fù)責(zé)。。。

由于本人水平有限，難免會(huì)有很多錯(cuò)誤，希望大家多多捧場(chǎng)，多多指教。。

文章來(lái)源:http://x-spirit.spaces.live.com/Blog/cns!CC0B04AE126337C0!282.entry

飛鴿傳書(shū)（IP Messenger,簡(jiǎn)為IPMsg）是一個(gè)小巧方便的即時(shí)通信軟件，它適合用于局域網(wǎng)內(nèi)甚至廣域網(wǎng)間進(jìn)行實(shí)時(shí)通信和文檔共享。特別是在局域網(wǎng)內(nèi)傳送文件/文件夾的速度非常快！

• IPMsg 是一款局域網(wǎng)內(nèi)即時(shí)通信軟件, 基于 TCP/IP(UDP).
• 可運(yùn)行于多種操作平臺(tái)(Win/Mac/UNIX/Java), 并實(shí)現(xiàn)跨平臺(tái)信息交流.
• 不需要服務(wù)器支持.
• 支持文件/文件夾的傳送 (2.00版以上)
• 通訊數(shù)據(jù)采用 RSA/Blofish 加密 (2.00版以上)
• 十分小巧, 簡(jiǎn)單易用, 而且你可以完全免費(fèi)使用它
• 目前已有的版本包括: Win32, Win16, MacOS, MacOSX, X11, GTK, GNOME,Java 等, 并且公開(kāi)源代碼。

本文演示了如何使用Java的net包，向IPMSG客戶端發(fā)送消息。
IPMSG Command 常量定義如下：

1 /*==========?Constant?Value?==========*/
?2 public static final long IPMSG_COMMASK?= 0x000000ff;
?3 public static final long IPMSG_OPTMASK?= 0xffffff00;
?4 public static final long IPMSG_NOOPERATION?= 0x00000000;
?5 public static final long IPMSG_BR_ENTRY?= 0x00000001;
?6 public static final long IPMSG_BR_EXIT?= 0x00000002;
?7 public static final long IPMSG_ANSENTRY?= 0x00000003;
?8 public static final long IPMSG_BR_ABSENCE?= 0x00000004;
?9
10
11
12 public static final long IPMSG_BR_ISGETLIST?= 0x00000018;
13 public static final long IPMSG_OKGETLIST?= 0x00000015;
14 public static final long IPMSG_GETLIST?= 0x00000016;
15 public static final long IPMSG_ANSLIST?= 0x00000017;
16
17 public static final long IPMSG_SENDMSG?= 0x00000020;
18 public static final long IPMSG_RECVMSG?= 0x00000021;
19
20 public static final long IPMSG_READMSG?= 0x00000030;
21 public static final long IPMSG_DELMSG?= 0x00000031;
22
23 public static final long IPMSG_GETINFO?= 0x00000040;
24 public static final long IPMSG_SENDINFO?= 0x00000041;
25
26 //?other?opt
27 public static final long IPMSG_ABSENCEOPT?= 0x00000100;
28 public static final long IPMSG_SERVEROPT?= 0x00000200;
29 public static final long IPMSG_DIALUPOPT?= 0x00010000;
30
31 //?send?opt
32 public static final long IPMSG_SENDCHECKOPT?= 0x00000100;
33 public static final long IPMSG_SECRETOPT?= 0x00000200;
34 public static final long IPMSG_BROADCASTOPT?= 0x00000400;
35 public static final long IPMSG_MULTICASTOPT?= 0x00000800;
36 public static final long IPMSG_NOPOPUPOPT?= 0x00001000;
37 public static final long IPMSG_AUTORETOPT?= 0x00002000;
38 public static final long IPMSG_RETRYOPT?= 0x00004000;
39 public static final long IPMSG_PASSWORDOPT?= 0x00008000;
40 public static final long IPMSG_NOLOGOPT?= 0x00020000;
41 public static final long IPMSG_NEWMUTIOPT?= 0x00040000;
42
43 public static final int?MAXBUF?= 8192;
44 /*==========?end?==========*/

IPMSG收發(fā)數(shù)據(jù)包的格式（一行）：

1 version(IPMSG版本):no(消息編號(hào)，可以用系統(tǒng)時(shí)間):user(發(fā)送消息的用戶名):host(發(fā)送消息的主機(jī)名):command(上述?Command?常量，可以用?|?組合多個(gè)值):msg(消息內(nèi)容)

示例(向IPMSG發(fā)送消息，需要先打開(kāi)對(duì)方的IPMSG)：

1 import java.io.IOException;
?2 import java.net.DatagramPacket;
?3 import java.net.DatagramSocket;
?4 import java.net.InetAddress;
?5 import java.net.SocketException;
?6 import java.net.UnknownHostException;
?7 import java.util.Date;
?8
?9 /**
10 ?*?@author?亂?7?8?糟?http://blog.csdn.net/comstep
11 */
12 public class?TestIPMSG
13 {
14 public static void?main(String[]?args)
15 ??{
16 ????DatagramSocket?socket;
17 ????InetAddress?address;
18
19 long IPMSG_SENDMSG?= 0x00000020;
20
21 ????String?SENDER?= "亂?7?8?糟";
22 ????String?HOST?= "Localhost";
23 ????String?MSG_CONTENT?= "Hello?World!";
24
25 try
26 ????{
27 ??????socket?= new?DatagramSocket();
28 ??????address?=?InetAddress.getByName("192.168.1.20");// 發(fā)送給消息的地址
29
30 /**
31 ???????*?IPMSG收發(fā)數(shù)據(jù)包的格式（一行）：
32 ???????*?
33 ???????*?version(IPMSG版本):no(消息編號(hào)，可以用系統(tǒng)時(shí)間):user(發(fā)送消息的用戶名):
34 ???????*?host(發(fā)送消息的主機(jī)名):command(上述?Command?常量，可以用?|?組合多個(gè)值):
35 ???????*?msg(消息內(nèi)容)
36 ???????*?
37 */
38 byte[]?buffer?=?("1:" + new?Date().getTime()?+ ":" +?SENDER?+ ":" +?HOST
39 + ":" + IPMSG_SENDMSG?+ ":" +?MSG_CONTENT).getBytes();
40
41 ??????DatagramPacket?packet?= new?DatagramPacket(buffer,?buffer.length,
42 ??????????address,?2425);
43 ??????socket.send(packet);?//?發(fā)送報(bào)文
44
45 ??????packet?= new?DatagramPacket(buffer,?buffer.length);
46 ??????socket.receive(packet);//?接收回應(yīng)
47
48 ??????String?message?= new?String(packet.getData());?//?得到報(bào)文信息
49
50 ??????System.out.println(message);?//?顯示對(duì)方返回的信息
51 ????}
52 catch?(UnknownHostException?e)
53 ????{
54 ??????e.printStackTrace();
55 ????}
56 catch?(SocketException?e)
57 ????{
58 ??????e.printStackTrace();
59 ????}
60
61 catch?(IOException?e)
62 ????{
63 ??????e.printStackTrace();
64 ????}
65
66 ??}
67
68 }
69

你可以在 SourceForge 找到開(kāi)源的 IP MSG for Java
http://blog.csdn.net/comstep

文章來(lái)源:http://x-spirit.spaces.live.com/Blog/cns!CC0B04AE126337C0!278.entry

?

?

受http://www.oreillynet.com/onjava/blog/2007/05/javafx_first_steps_hello_onjav_1.html這篇文章的啟發(fā)，加上想學(xué)習(xí)一下JavaFX，就在上面那篇文章的基礎(chǔ)上，做了一個(gè)簡(jiǎn)易的RSS閱讀器，其界面類似于Adobe Flex 2的一個(gè)demo：進(jìn)入http://try.flex.org/index.cfm，找到Blog Reader的demo。

讀取RSS feed并沒(méi)有什么問(wèn)題，使用rome：

java 代碼

1. package?rssreader; ??
3. import?com.sun.syndication.feed.synd.SyndEntry; ??
4. import?com.sun.syndication.feed.synd.SyndFeed; ??
5. import?com.sun.syndication.io.FeedException; ??
6. import?com.sun.syndication.io.SyndFeedInput; ??
7. import?com.sun.syndication.io.XmlReader; ??
8. import?java.io.IOException; ??
9. import?java.net.MalformedURLException; ??
10. import?java.net.URL; ??
12. public class?RssReader?{ ??
13. private?URL?url; ??
14. private?Integer?titleLength?=?50; ??
16. public?RssReader()?{ ??
18. ????} ??
20. public?SyndEntry[]?load(String?urlString)?throws?IllegalArgumentException,?FeedException,?IOException?{ ??
21. if?(urlString?!=?null?&&?urlString?!=?"")?{ ??
22. try?{ ??
23. ????????????????url?=?new?URL(urlString); ??
24. ????????????}?catch?(MalformedURLException?e)?{ ??
25. ????????????????e.printStackTrace(); ??
26. return null; ??
27. ????????????} ??
28. ????????} ??
29. if?(url?==?null)?{ ??
30. return null; ??
31. ????????} ??
32. ????????SyndFeedInput?input?=?new?SyndFeedInput(); ??
33. ????????SyndFeed?feed?=?input.build(new?XmlReader(url)); ??
34. ????????SyndEntry[]?entries?=?(SyndEntry[])?feed.getEntries().toArray(new?SyndEntry[0]); ??
36. for(?SyndEntry?entry?:?entries?)?{ ??
37. ????????????entry.setTitle(?entry.getTitle().length()?>?titleLength???entry.getTitle().substring(0,?titleLength?-?3?)?+?"..."?:?entry.getTitle()?); ??
38. ????????}? ??
40. return?entries; ??
41. ????} ??
44. } ??

使用JavaFX構(gòu)建UI：

JavaFX代碼

1. package?rssreader; ??
3. import?javafx.ui.*; ??
4. import?javafx.ui.canvas.*; ??
5. import?javax.swing.JComponent; ??
6. import?com.sun.syndication.feed.synd.SyndEntry; ??
8. var?reader:RssReader?=?READER; ??
10. class?RssReaderModel?{ ??
11. ????attribute?rssUrl:?String; ??
12. ????attribute?rssEntries:?SyndEntry*; ??
13. ????attribute?rssContent:?String?; ??
14. ????attribute?rssSelectedIndex:?Integer; ??
15. } ??
17. var?model?=?RssReaderModel?{ ??
18. ????rssUrl:?"http://woodstudio.javaeye.com/blog/rss_blog/alexcheng", ??
19. }; ??
22. var?panel?=?GroupPanel?{ ??
23. var?row1?=?Row?{} ??
24. var?row2?=?Row?{} ??
25. var?col?=?Column?{} ??
26. ?????rows:?[row1,?row2] ??
27. ?????columns:?col ??
28. ?????content:? ??
29. ?????????[ ??
30. ????????????GroupPanel??{ ??
31. ????????????????row:?row1 ??
32. ????????????????column:?col ??
33. var?row?=?Row?{} ??
34. var?labelCol?=??new?Column ??
35. var?urlCol?=??new?Column ??
36. var?butCol?=??new?Column ??
37. ????????????????rows:?row ??
38. ????????????????columns:?[labelCol,?urlCol,?butCol] ??
39. ????????????????content: ??
40. ????????????????[ ??
41. ????????????????????SimpleLabel?{ ??
42. ????????????????????????row:?row ??
43. ????????????????????????column:?labelCol ??
44. ????????????????????????text:?"RSS?URL:"
45. ????????????????????}, ??
46. ?????????????????????TextField?{ ??
47. ????????????????????????row:?row ??
48. ????????????????????????column:?urlCol ??
49. ????????????????????????columns:?60 ??
50. ????????????????????????value:?bind?model.rssUrl ??
51. ????????????????????}, ??
52. ????????????????????Button?{ ??
53. ????????????????????????row:?row ??
54. ????????????????????????column:?butCol ??
55. ????????????????????????text:?"Get?Entries"
56. ????????????????????????action:?operation()?{ ??
57. ????????????????????????????model.rssEntries?=?reader.load(model.rssUrl);??????????? ??
58. ????????????????????????} ??
59. ????????????????????} ??
60. ????????????????] ??
61. ????????????}, ??
62. ????????????SplitPane???{ ??
63. ????????????????row:?row2 ??
64. ????????????????column:?col ??
65. ????????????????orientation:?HORIZONTAL ??
66. ????????????????content: ??
67. ????????????????[ ??
68. ????????????????????SplitView??{ ??
69. ????????????????????????weight:?0.3 ??
70. ????????????????????????content:???? ??
71. ????????????????????????????Table?{ ??
72. ????????????????????????????????????columns: ??
73. ????????????????????????????????????[ ??
74. ????????????????????????????????????????TableColumn?{ ??
75. ????????????????????????????????????????????text:?"Title"
76. ????????????????????????????????????????}, ??
77. ????????????????????????????????????????TableColumn?{ ??
78. ????????????????????????????????????????????text:?"Date"
79. ????????????????????????????????????????}, ??
80. ????????????????????????????????????] ??
81. ????????????????????????????????????cells?:?bind?foreach?(entry?in?model.rssEntries) ??
82. ????????????????????????????????????????????[ ??
83. ????????????????????????????????????????????????TableCell?{ ??
84. ????????????????????????????????????????????????????text:?bind?entry.title ??
85. ????????????????????????????????????????????????}, ??
86. ????????????????????????????????????????????????TableCell?{ ??
87. ????????????????????????????????????????????????????text:?bind?entry.publishedDate.toLocaleString() ??
88. ????????????????????????????????????????????????} ??
89. ????????????????????????????????????????????] ??
90. ????????????????????????????????????selection:?bind?model.rssSelectedIndex ??
91. ????????????????????????????????}??? ??
92. ????????????????????}, ??
93. ????????????????????SplitView??{ ??
94. ????????????????????????weight:?0.7 ??
95. ????????????????????????content: ??
96. ????????????????????????????EditorPane???{ ??
97. ????????????????????????????????opaque:?true
98. ????????????????????????????????contentType:?HTML ??
99. ????????????????????????????????editable:?false
100. ????????????????????????????????text:?bind?model.rssContent ??
101. ????????????????????????????} ??
102. ????????????????????????} ??
103. ????????????????] ??
104. ????????????} ??
105. ?????????]? ??
106. }; ??
108. trigger?on?(RssReaderModel.rssSelectedIndex?=?value)?{ ??
109. var?desc?=?rssEntries[value].description.value; ??
110. ????rssContent?=?"?{desc}?";? ??
111. } ??
113. MY_CONTAINER:JComponent.add(panel.getComponent()); ??

接著就是使用JSR223的scripting framework來(lái)執(zhí)行：

java 代碼

1. package?rssreader; ??
3. import?javax.script.Bindings; ??
4. import?javax.script.ScriptContext; ??
5. import?javax.script.ScriptEngine; ??
6. import?javax.script.ScriptEngineManager; ??
7. import?javax.script.SimpleScriptContext; ??
8. import?javax.swing.JFrame; ??
10. public class?Main?{ ??
12. /**
13. ?????*?@param?args
14. ?????*?@throws?Exception
15. ?????*/
16. public static void?main(String[]?args)?throws?Exception?{ ??
17. ????????RssReader?reader?=?new?RssReader(); ??
19. ????????JFrame?frame?=?new?JFrame( ??
20. "RSS?Reader?implemented?using?JavaFX?by?alexcheng"); ??
21. ????????frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); ??
22. ????????frame.setSize(800,?600); ??
24. ????????ClassLoader?loader?=?Thread.currentThread().getContextClassLoader(); ??
25. ????????ScriptEngineManager?manager?=?new?ScriptEngineManager(loader); ??
26. ????????ScriptEngine?engine?=?manager.getEngineByExtension("fx"); ??
28. ????????Bindings?bindings?=?engine.createBindings(); ??
29. ????????bindings.put("READER:rssreader.RssReader",?reader); ??
31. ????????bindings.put("MY_CONTAINER:javax.swing.JComponent",?frame ??
32. ????????????????.getContentPane()); ??
34. ????????ScriptContext?context?=?new?SimpleScriptContext(); ??
35. ????????context.setBindings(bindings,?ScriptContext.GLOBAL_SCOPE); ??
36. ????????context.setBindings(bindings,?ScriptContext.ENGINE_SCOPE); ??
37. ????????engine.setContext(context); ??
39. ????????String?script?=?"import?rssreader.FxMain;"; ??
40. ????????engine.eval(script); ??
42. ????????frame.setVisible(true); ??
43. ????} ??
45. } ??

最后的界面如下：

javafxrssreader.JPG

?描述:
?JavaFX RSS Reader

?文件大小:
?74 KB

?看過(guò)的:
?文件被下載或查看 28 次

文章來(lái)源:http://x-spirit.spaces.live.com/Blog/cns!CC0B04AE126337C0!274.entry

1。 Release Test
　　Purpose:
　　測(cè)試手機(jī)的基本功能是否實(shí)現(xiàn)，是否有進(jìn)一步測(cè)試的必要性
　　Attention:
　　Release Test的Test Case具有一定的典型性，主要是反映手機(jī)最基本功能的Test Case
　　本類測(cè)試只需要依據(jù)Test Case進(jìn)行測(cè)試，不需要進(jìn)一步發(fā)揮
　　如果有發(fā)現(xiàn)與Case無(wú)關(guān)的Error, 在測(cè)試通過(guò)后才可以填報(bào)Error Report
　　此類測(cè)試有一門(mén)檻值，即Test Case的Pass率達(dá)到一定值（如95%）才能宣布版本發(fā)布成功，進(jìn)入進(jìn)一步的測(cè)試，否則此版本無(wú)效。
　　除了門(mén)檻值外，如果重要功能模塊的Test Case沒(méi)通過(guò)，也會(huì)終止這個(gè)版本。
　　2 System Test
　　Full Round System Test
　　Purpose
　　對(duì)手機(jī)的所有功能進(jìn)行全面的測(cè)試(所有語(yǔ)言包)
　　由于Case不可能包含所有方面，所以測(cè)試時(shí)應(yīng)適度發(fā)揮，盡力完成全面測(cè)試
　　Common System Test (Medium or Minor)
　　Attention:
　　System Test一般分為兩個(gè)部分，“跑Case”和Free Test。
　　在測(cè)試初期，一般只需要按照Test Case測(cè)，把一些不可重現(xiàn)的Error都記錄下來(lái)。同時(shí)遇到Test Case的問(wèn)題或者不充分，應(yīng)該立即解決（和Team Leader或者Special List討論，補(bǔ)寫(xiě)Test Case）。在這一階段結(jié)束后，一般要寫(xiě)一個(gè)Summary Report。把這一階段的測(cè)試結(jié)果和遇到的問(wèn)題、自己的見(jiàn)解都寫(xiě)在里面（當(dāng)然是用English）。
　　當(dāng)所有Test Case都測(cè)完后，就進(jìn)入Free Test期間。這里的Free Test具有明確的目的性和范圍。一般來(lái)說(shuō)，這段時(shí)間的Free Test只需要測(cè)自己負(fù)責(zé)的模塊。而且Free Test還負(fù)責(zé)重現(xiàn)前期“跑Case”是遺留的不可重現(xiàn)的Error。
　　3 Focus Test
　　Purpose:
　　集中于一個(gè)或幾個(gè)點(diǎn)進(jìn)行測(cè)試(同System Test)

　　4 Stress Test
　　Purpose:
　　為了解決市場(chǎng)上發(fā)現(xiàn)的重大Error，而進(jìn)行的有針對(duì)性的強(qiáng)度測(cè)試
　　主要是利用邊緣測(cè)試（臨界測(cè)試）手段
　　Attention:
　　壓力測(cè)試，顧名思義，是給手機(jī)施加一定壓力，從而找出手機(jī)軟件上的Error。一般來(lái)說(shuō)，對(duì)手機(jī)施加的壓力主要有：
　　存儲(chǔ)壓力：由于手機(jī)采用的是棧式存儲(chǔ)，所以當(dāng)一個(gè)存儲(chǔ)塊滿了之后，如果程序員不做相應(yīng)處理或者處理不好的話，很容易造成其他存儲(chǔ)區(qū)被擦除，從而在UI上出現(xiàn)問(wèn)題（其他功能無(wú)法正常使用）。
　　邊界壓力：邊界一直是程序員最容易忽略的地方。
　　響應(yīng)能力壓力：有時(shí)候某個(gè)操作可能處理的時(shí)間很長(zhǎng)，在處理期間如果測(cè)試者再不斷地進(jìn)行其他操作的話，很容易出現(xiàn)問(wèn)題。
　　網(wǎng)絡(luò)流量壓力（如在接電話時(shí)進(jìn)行短信服務(wù)）等等。
　　在項(xiàng)目中，Stress Test有時(shí)也會(huì)用來(lái)重現(xiàn)不可重現(xiàn)的Error。
　　由于有不少不可重現(xiàn)的Error是由于Memory Leak(內(nèi)存泄漏)引起的，所以不停的重復(fù)同一個(gè)操作是重現(xiàn)一個(gè)不可重現(xiàn)的Error的一個(gè)好方法。
　　5 Free Test

　　Purpose:
　　測(cè)試System Test中沒(méi)有做完的不可重現(xiàn)Error
　　尋找平時(shí)沒(méi)有找到的忽略的Error
　　Attention:
　　在System Test階段所用的Free Test具有明顯的目的性和范圍
　　平時(shí)的Free Test從理論上應(yīng)該對(duì)所測(cè)試的范圍窮盡所有的測(cè)試方法。但是，這是不現(xiàn)實(shí)的。在實(shí)際項(xiàng)目中，主要有兩個(gè)方面是Free Test所需要重視的。
　　一是從UI Spec上找靈感。應(yīng)為T(mén)est Case是依據(jù)UI Spec寫(xiě)的，所以從UI Spec上突破是一個(gè)行之有效的方法。UI Spec有一定的探索深度，加大探索深度，是一種突破的途徑；另外同一個(gè)功能用其他不同的方法去實(shí)現(xiàn)，也是一種突破途徑。
　　二是多關(guān)注不同F(xiàn)eature之間的Interaction。這是手機(jī)軟件相對(duì)比較容易出問(wèn)題，而Test Case又很少能反映的地方。這是一個(gè)很大的Free Test空間。
文章來(lái)源:http://x-spirit.spaces.live.com/Blog/cns!CC0B04AE126337C0!269.entry

JavaFX Script? （下文中成為JavaFX）語(yǔ)言是一種聲明式的靜態(tài)類型編程語(yǔ)言。它具有第一級(jí)函數(shù)（first-class functions）、聲明式的語(yǔ)法、列表推導(dǎo)（list-comprehensions）及基于依賴關(guān)系的增量式求值（incremental dependency-based evaluation）等特征。JavaFX 腳本式語(yǔ)言特別適用于Java2D swing GUI組件，它允許簡(jiǎn)單地創(chuàng)建圖形界面。

譯者注：第一級(jí)函數(shù)指函數(shù)被當(dāng)作對(duì)象對(duì)待，可以在運(yùn)行時(shí)賦值、傳遞和返回。詳見(jiàn)wikipedia上的解釋。

譯者注：列表推導(dǎo)指一種在函數(shù)語(yǔ)言中的表達(dá)式，它表示了在一個(gè)或者多個(gè)列表的成員（被選擇的）進(jìn)行某種操作的結(jié)果。它被稱為“syntactic sugar”，即為開(kāi)發(fā)者提供了便捷的多種函數(shù)的應(yīng)用組合。詳見(jiàn)FOLDC對(duì)list comprehension的解釋。

本文檔給出了JavaFX 腳本式編程語(yǔ)言的非正式描述。

就語(yǔ)言方面來(lái)說(shuō)，出現(xiàn)了Java FX script 項(xiàng)目。Java FX是很靈巧的，它提供了一個(gè)高級(jí)的腳本接口，運(yùn)行在Java 2D的API上。從用戶的角度來(lái)看，他們不需要編寫(xiě)Java代碼，不需要深入理解復(fù)雜的線程，Java 2D，Swing類的層次結(jié)構(gòu)，定時(shí)框架結(jié)構(gòu)（timing framework）等等。相反，他們只是編寫(xiě)腳本語(yǔ)言和描繪出所需要的GUI，包括活波的音響效果，圖形效果，比如說(shuō)梯度或者音樂(lè)，和數(shù)據(jù)綁定等等，這些都建立在一個(gè)基礎(chǔ)API上。
??? 這里有許多的工具幫助你學(xué)習(xí)syntax語(yǔ)言，相關(guān)資源這個(gè)從這個(gè)網(wǎng)站獲得；Java FX研發(fā)小組的目標(biāo)就是提供syntax語(yǔ)言，和一些關(guān)于Java FX的用戶體驗(yàn)，這些用戶包括美術(shù)設(shè)計(jì)員和那些對(duì)應(yīng)用程序可視界面美觀感興趣的民眾。當(dāng)前，Java FX某種程度上作為第四步產(chǎn)生的語(yǔ)言在運(yùn)行，因?yàn)槭紫仁墙忉屍鲗X腳本創(chuàng)建成為Java代碼，然后再調(diào)用適當(dāng)?shù)腏ava 2D API。該小組長(zhǎng)期的目標(biāo)是將FX腳本直接編譯成字節(jié)碼。
??? Java FX添加到桌面Java是一件非常好的事情，但是，這得取決于是否有這樣的一種JRE的存在，它能運(yùn)行Java FX生成的代碼。有些人認(rèn)為FX已經(jīng)進(jìn)軍到RIA(rich Internet application)領(lǐng)域，和Adobe公司的 Flex一較高下。但是，目前還是有一些難題需要解決，舉個(gè)例子，如何才能讓桌面Java的安裝體驗(yàn)和運(yùn)行時(shí)間性能比得上其它的RIA框架。還好，這種問(wèn)題正在被其他的項(xiàng)目解決，這個(gè)項(xiàng)目名稱就是Java kernel。
??? Java kernel主動(dòng)承認(rèn)這么一個(gè)事情，即大多數(shù)的Java應(yīng)用程序都是只有JRE的部分大小，如Limewire（一個(gè)文件共享的桌面應(yīng)用程序），它只有JRE的三分之一大小。Kernel將會(huì)對(duì)JRE重新打包，使得只下載應(yīng)用程序所需要的部分JRE。每個(gè)程序所需要的基本部分將會(huì)被下載，作為JRE啟動(dòng)所需要的最小部分，其他的部分根據(jù)需要下載，或者根據(jù)ClassNotFound異常信息，下載缺失的類。這將是一個(gè)巨大的好消息幫助桌面Java應(yīng)用程序瘦身，同時(shí)還能使得桌面Java應(yīng)用程序執(zhí)行的更為有效。除了解決如何下載的問(wèn)題外，kernel還非常關(guān)注Java程序的啟動(dòng)性能。
??? 在先前的kernel幾個(gè)版本，熱啟動(dòng)時(shí)間（warm start times）減少了很多，但是，在應(yīng)用程序調(diào)用main(String[])前，冷啟動(dòng)JRE仍然需要延誤許多秒的時(shí)間。Java kernel正在嘗試有效的處理冷啟動(dòng)，將冷啟動(dòng)轉(zhuǎn)變?yōu)闊釂?dòng)，通過(guò)一些相關(guān)的技術(shù)，如預(yù)加載（pre-loading）JRE，從硬盤(pán)讀入到內(nèi)存，還有一個(gè)操作系統(tǒng)服務(wù)，這個(gè)服務(wù)的功能就是監(jiān)視可分配的內(nèi)存來(lái)加載JRE，使得用戶獲得最佳的性能。出了這些，kernel還提供了一個(gè)新的瀏覽器插件，提供給Web 開(kāi)發(fā)者更多的關(guān)于桌面運(yùn)行信息，可獲得的JRE水平等等。
???? 對(duì)于桌面Java來(lái)說(shuō)，Java kernel 和Java FX兩大好消息。說(shuō)Kernel是一個(gè)非常好的技術(shù)，是因?yàn)樗姓J(rèn)了Swing已經(jīng)到了一個(gè)非常成熟的階段，并且?guī)椭_(kāi)發(fā)這如何將他們的Java應(yīng)用程序更為快速，更為有效的搬到用戶桌面上。說(shuō)FX是兩外一個(gè)非常好的消息，是因?yàn)樗鼮镴ava開(kāi)發(fā)者打開(kāi)了新篇章，特別是那些愿意使用腳本語(yǔ)言和做一些高級(jí)的，活波的，圖形效果的開(kāi)發(fā)者，他們只需要寫(xiě)簡(jiǎn)單幾行代碼就可以完成。我相信這兩項(xiàng)技術(shù)將會(huì)使得更多的應(yīng)用程序用Java語(yǔ)言編寫(xiě)，運(yùn)行在用戶的機(jī)器上，同時(shí)，對(duì)于用戶和開(kāi)發(fā)者來(lái)說(shuō)，應(yīng)用程序變得更快，更簡(jiǎn)單。

相關(guān)學(xué)習(xí)資料

https://openjfx.dev.java.net/JavaFX_Programming_Language_CN.html

https://openjfx.dev.java.net/JavaFX_Programming_Language.html

https://openjfx.dev.java.net/Getting_Started_With_JavaFX.html

https://openjfx.dev.java.net/

文章來(lái)源:http://x-spirit.spaces.live.com/Blog/cns!CC0B04AE126337C0!266.entry

文章來(lái)源:http://x-spirit.spaces.live.com/Blog/cns!CC0B04AE126337C0!203.entry