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(339) 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: 清水县| 罗田县| 新泰市| 筠连县| 荣成市| 千阳县| 镇赉县| 崇阳县| 彰武县| 利川市| 金川县| 千阳县| 弥渡县| 独山县| 墨竹工卡县| 淮滨县| 金川县| 桃源县| 宜兴市| 新巴尔虎右旗| 五华县| 乐陵市| 平湖市| 滦平县| 宜兰县| 兴义市| 开封市| 紫云| 四会市| 抚松县| 那曲县| 稷山县| 景洪市| 建始县| 甘洛县| 甘谷县| 银川市| 卢湾区| 洪湖市| 永仁县| 广南县|