Sung in Blog

                     一些技術(shù)文章 & 一些生活雜碎

          java.lang
          Class StringBuffer

          java.lang.Object
            |
            +--java.lang.StringBuffer
          
          All Implemented Interfaces:
          CharSequence, Serializable

          public final class StringBuffer
          extends Object
          implements Serializable, CharSequence

          A string buffer implements a mutable sequence of characters. A string buffer is like a String, but can be modified. At any point in time it contains some particular sequence of characters, but the length and content of the sequence can be changed through certain method calls.

          String buffers are safe for use by multiple threads. The methods are synchronized where necessary so that all the operations on any particular instance behave as if they occur in some serial order that is consistent with the order of the method calls made by each of the individual threads involved.

          String buffers are used by the compiler to implement the binary string concatenation operator +. For example, the code:

               x = "a" + 4 + "c"
           

          is compiled to the equivalent of:

               x = new StringBuffer().append("a").append(4).append("c")
                                     .toString()
           
          which creates a new string buffer (initially empty), appends the string representation of each operand to the string buffer in turn, and then converts the contents of the string buffer to a string. Overall, this avoids creating many temporary strings.

          The principal operations on a StringBuffer are the append and insert methods, which are overloaded so as to accept data of any type. Each effectively converts a given datum to a string and then appends or inserts the characters of that string to the string buffer. The append method always adds these characters at the end of the buffer; the insert method adds the characters at a specified point.

          For example, if z refers to a string buffer object whose current contents are "start", then the method call z.append("le") would cause the string buffer to contain "startle", whereas z.insert(4, "le") would alter the string buffer to contain "starlet".

          In general, if sb refers to an instance of a StringBuffer, then sb.append(x) has the same effect as sb.insert(sb.length(), x).

          Every string buffer has a capacity. As long as the length of the character sequence contained in the string buffer does not exceed the capacity, it is not necessary to allocate a new internal buffer array. If the internal buffer overflows, it is automatically made larger.

          Since:
          JDK1.0
          See Also:
          ByteArrayOutputStream, String, Serialized Form
          posted on 2005-10-26 14:26 Sung 閱讀(332) 評論(1)  編輯  收藏 所屬分類: Java

          FeedBack:
          # re: Class StringBuffer
          2005-10-26 14:43 | Sung
          Strings are constant; their values cannot be changed after they are created. String buffers support mutable strings. Because String objects are immutable they can be shared.  回復(fù)  更多評論
            
          主站蜘蛛池模板: 原阳县| 江油市| 临武县| 柳州市| 钟山县| 泾源县| 长子县| 汾阳市| 新宾| 乌兰察布市| 琼海市| 类乌齐县| 昌都县| 江北区| 吉林市| 唐海县| 龙门县| 凤城市| 屯昌县| 叶城县| 辽宁省| 资源县| 城固县| 沙河市| 平山县| 英吉沙县| 乾安县| 信阳市| 盐津县| 麟游县| 康保县| 印江| 五常市| 友谊县| 利辛县| 方山县| 台北县| 沐川县| 林芝县| 济南市| 大洼县|