这类操作大同小异，但是，高手却能从String,StringBuilder,StringBuffer的应用场景和性能上，分析出其在JAVA编译和JVM上的实现过程差别。

我在CSDN上就看到一个高手分析过。

http://blog.csdn.net/clam_clam/article/details/6831345

http://www.cnblogs.com/dolphin0520/p/3778589.html

public class StringBufferDemo {  public static void main(String[] args) {    System.out.println("----------------------");    createString(new StringBuffer("hello java"));    System.out.println("----------------------");    deleteString(new StringBuffer("hello java"));    System.out.println("----------------------");    replaceString(new StringBuffer("hello java"));  }  public static void createString(StringBuffer stringBuffer) {    stringBuffer.append("hello").append("java").append(520).append(true);    System.out.println(stringBuffer);    stringBuffer.insert(0, "heima,");    System.out.println(stringBuffer);  }  public static void deleteString(StringBuffer stringBuffer) {    stringBuffer.delete(0, 6);    System.out.println(stringBuffer);    stringBuffer.deleteCharAt(1);    System.out.println(stringBuffer);  }  public static void replaceString(StringBuffer stringBuffer) {    stringBuffer.replace(6, stringBuffer.length(), "world");    System.out.println(stringBuffer);    stringBuffer.setCharAt(5, ',');    System.out.println(stringBuffer);    stringBuffer.reverse();    System.out.println(stringBuffer);  }}