程序代码：

package test_demon;

public class try1 {
    String str1 =new String("123");
   

    public void change(String str)
    {
        str = "ok";
    }

public static void main(String[] args) {
        try1 ex= new try1();
        ex.change(ex.str1);
        System.out.print(ex.str1);
    }
}