编写程序使用类StringBuffer的replace方法将字符串”Mary was a ”改为”Mary had a book.”(程序设计题)

import java.util.*; public class String_test { public static void main(String args[]) { StringBuffer str1=new StringBuffer(“Mary was a”); StringBuffer str2=str1.replace(5,10,”had a book.”); System.out.println(str2); } }