排序的算法是我们最常用的算法，初学E序Q每个h都尝试过排序。但只是局限于单的排序?br />如将下列数字q行排序
1Q?Q?Q?Q?Q?
于是我们得出l果
1Q?Q?Q?Q?Q?
下列字母（字符Q进行排?br />a,i,e,f,w,s
于是我们得出l果
a,e,f,i,s,w
但是我们遇到的情况就不是如此单了。如l公叔R的商品进行排序，我们很轻易的惛_按照商品的名U排序不完了，而且单明了。但现实q如我们怿般简单。同一商品名称可以有不同的ҎQ进货时_可能q会有单L不同。显然只Ҏ商品名称排序是不合理的?br />
再D个简单例子然后用E序实现。如公司要将员工q行排序Q不要说领导排在前面Q，假设我们的需求比较复杂。先q行姓排序，谁的姓拼音靠前，谁就排前面。然后对名字q行排序。恩.如果同名Q女性排前头。如果名字和性别都相同，q龄的排前头。okQ一个也不算复杂的需求?br />
如果对java比较熟悉的会知道java.util.Comparator 接口。要实现里面的函?br /> int compare(Object o1, Object o2) q回一个基本类型的整型Q返回负数表Co1 于o2Q返? 表示o1和o2相等Q返回正数表Co1大于o2?br />
于是我们设计的h员类要有几个变量Qfirstname,lastname,sex,age分别表示姓，名，性别Q年龄?br />
public class Person {
String firstname,lastname;
Boolean sex;
Integer age;
public Person(String firstname,String lastname,Boolean sex,Integer age) {
this.firstname = firstname;
this.lastname = lastname;
this.sex = sex;
this.age = age;
}
public String getFirstName() {
return firstname;
}
public String getLastName() {
return lastname;
}
public Boolean getSex() {
return sex;
}
public Integer getAge() {
return age;
}
//Z输入方便Q重写了toString()
public String toString()
{
return firstname +" "+lastname+" "+(sex.booleanValue()?"?:"?)+" "+age;
}
}
//end person
下面是要实现比较?br />
public class Comparators {
public static java.util.Comparator getComparator() {
return new java.util.Comparator() {
public int compare(Object o1, Object o2) {
if (o1 instanceof String) {
return compare( (String) o1, (String) o2);
}
else if (o1 instanceof Integer) {
return compare( (Integer) o1, (Integer) o2);
}
else if (o1 instanceof Person) {
return compare( (Person) o1, (Person) o2);
}
else {
System.err.println("未找到合适的比较?);
return 1;
}
}
public int compare(String o1, String o2) {
String s1 = (String) o1;
String s2 = (String) o2;
int len1 = s1.length();
int len2 = s2.length();
int n = Math.min(len1, len2);
char v1[] = s1.toCharArray();
char v2[] = s2.toCharArray();
int pos = 0;
while (n-- != 0) {
char c1 = v1[pos];
char c2 = v2[pos];
if (c1 != c2) {
return c1 - c2;
}
pos++;
}
return len1 - len2;
}
public int compare(Integer o1, Integer o2) {
int val1 = o1.intValue();
int val2 = o2.intValue();
return (val1 < val2 ? -1 : (val1 == val2 ? 0 : 1));
}
public int compare(Boolean o1, Boolean o2) {
return (o1.equals(o2)? 0 : (o1.booleanValue()==true?1:-1));
}
public int compare(Person o1, Person o2) {
String firstname1 = o1.getFirstName();
String firstname2 = o2.getFirstName();
String lastname1 = o1.getLastName();
String lastname2 = o2.getLastName();
Boolean sex1 = o1.getSex();
Boolean sex2 = o2.getSex();
Integer age1 = o1.getAge();
Integer age2 = o2.getAge();
return (compare(firstname1, firstname2) == 0 ?
(compare(lastname1, lastname2) == 0 ? (compare(sex1, sex2) == 0 ? (compare(age1, age2) == 0 ? 0 :
compare(age1, age2)) :
compare(sex1, sex2)) :
compare(lastname1, lastname2)) :
compare(firstname1, firstname2));
}
};
}
}
以上代码有可能因为浏览器的布局自动换行?br />compare(Person o1, Person o2)的返回值看h比较别扭。最单的?br />
public int compare(Boolean o1, Boolean o2) {
return (o1.equals(o2)? 0 : (o1.booleanValue()==true?1:-1));
}
o1和o2相等q回0Q否则o1如果是true pCo1大于o2?br />
再尝试输出结果看?br />
public class Main {
public Main() {
}
public static void main(String[] args) {
Person[] person = new Person[] {
new Person("ouyang", "feng", Boolean.TRUE, new Integer(27)),
new Person("zhuang", "gw", Boolean.TRUE, new Integer(27)),
new Person("zhuang", "gw", Boolean.FALSE, new Integer(27)),
new text.Person("zhuang", "gw", Boolean.FALSE, new Integer(2)),
};
for (int i = 0; i < person.length; i++) {
System.out.println("before sort=" + person[i]);
}
java.util.Arrays.sort(person, Comparators.getComparator());
for (int i = 0; i < person.length; i++) {
System.out.println("after sort=" + person[i]);
}
}
}
输出l果Q?br />
before sort=ouyang feng ?27
before sort=zhuang gw ?27
before sort=zhuang gw ?27
before sort=zhuang gw ?2
after sort=ouyang feng ?27
after sort=zhuang gw ?2
after sort=zhuang gw ?27
after sort=zhuang gw ?27
仔细理解java的Comparator会给你写排序带来很大帮助
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- Build AJAX apps in the Java language
Google Web Toolkit (GWT) is a Java software development framework that makes writing AJAX applications like Google Maps and Gmail easy for developers who don't speak browser quirks as a second language. Writing dynamic web applications today is a tedious and error-prone process; you spend 90% of your time working around subtle incompatabilities between web browsers and platforms, and JavaScript's lack of modularity makes sharing, testing, and reusing AJAX components difficult and fragile.
GWT lets you avoid many of these headaches while offering your users the same dynamic, standards-compliant experience. You write your front end in the Java programming language, and the GWT compiler converts your Java classes to browser-compliant JavaScript and HTML.
GWT的特?
-
To communicate from your web application to your web server, you just need to define serializable Java classes for your request and response. In production, GWT automatically serializes the request and deserializes the response from the server. GWT's RPC mechanism can even handle polymorphic class hierarchies, and you can throw exceptions across the wire.
-
No, AJAX applications don't need to break the browser's back button. GWT lets you make your site more usable by easily adding state to the browser's back button history.
-
In production, your code is compiled to JavaScript, but at development time it runs in the Java virtual machine. That means when your code performs an action like handling a mouse event, you get full-featured Java debugging, with exceptions and the advanced debugging features of IDEs like Eclipse.
-
Your GWT applications automatically support IE, Firefox, Mozilla, Safari, and Opera with no browser detection or special-casing within your code in most cases.
-
If GWT's class library doesn't meet your needs, you can mix handwritten JavaScript in your Java source code using our JavaScript Native Interface (JSNI).
and there is a feedback that it's not better than dojo.
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class MyPage extends WebPage {
private String criteria;
//getter/setter for criteria
public MyPage() {
IModel listModel=new LoadableDetachableModel() {
Object load() {
UserService service=...get user service;
List users=service.findUsersFiltered(criteria);
return users;
}
}
add(new ListView("users", listModel) {....});
// so here we have the listview that will show a list that is filtered on page's criteria property. now we hookup our dropdownchoice in such a way that it modifies this property and when the page refreshes so will the listview because it is using a detachble model.
Form form=new Form();
add(form);
List filters=new ArrayList();
filters.add("a");
filters.add("b");
form.add(new DropDownChoice("filter", new PropertyModel(this, "criteria"), filters) {
wantOnChangeNotifiaction() { return true; });
// here we glue dropdown choice to our criteria property via the property model
}}
and thats it. to overview what we have done:
the listview "pulls" its filter from the criteria property on the page and uses a detachable model so that it refreshes on every request
dropdown choice puts its selection into the criteria property
so the listview is glued to the dropdown choice by sharing a property
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