java基础--常用类

package com.atguigu.java;

import org.junit.Test;


public class StringTest {

    
    @Test
    public void test1(){
        String s1 = "abc";
        String s2 = "abc";

        s1="hello";

        System.out.println(s1 == s2);       //比较s1和s2的地址值

        System.out.println(s1);
        System.out.println(s2);

        System.out.println("*******************************");

        String s3="abc";

        s3+="def";

        System.out.println(s3);

        String s4 = "abc";
        String s5 = s4.replace('a', 'm');
        System.out.println(s4);
        System.out.println(s5);

    }


}