insert() 函数表示在字符串中插入字符串

StringBuffer insert(int index,String str)

import java.lang.*;
public class insertdemo {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
        StringBuffer s=new StringBuffer("kbjkabjkvbk");
        s.insert(3,"abc");
        System.out.println(s);
	}

}