1  import java.text.*; 2   public class Gxjun 3  { 4     public static void main(String atgs[]) 5     { 6        StringBuffer str= new StringBuffer();  7        str.append("大家好"); 8        System.out.println("str:"+str); 9        System.out.println("length:"+str.length());  10        System.out.println("capacity:"+str.capacity());       11        str.setCharAt(0,'w');12        str.setCharAt(1,'e');13        System.out.println(str);14        str.insert(2, "are all");15        System.out.println(str);16        int index=str.indexOf("好");17        str.replace(index, str.length(),"right");18        System.out.println(str); 19     }20  }