String 深浅拷贝的测试---有待继续测试

public class TestString {

    void test1() {
        // TODO Auto-generated method stub
        String str = new String();
        str = "12345";

        String STR = "12345";
        System.out.println(str == STR);

        String str_1 = str;

        String str_2 = null;
        str_2 = str;

        String str_3 = new String();
        str_3 = str;

        String str_4 = new String(str);

        System.out.println("str:" + str);

        System.out.println("str_1:" + str_1);
        System.out.println("str == str_1:" + str == str_1);

        System.out.println("str_2:" + str_2);
        System.out.println("str == str_2:" + str == str_2);

        System.out.println("str_3:" + str_3);
        System.out.println("str == str_3:" + str == str_3);

        System.out.println("str_4:" + str_4);
        System.out.println("str == str_4:" + str == str_4);

        str = "2345678";

        System.out.println("str:" + str);

        System.out.println("str_1:" + str_1);
        System.out.println("str == str_1:" + str == str_1);

        System.out.println("str_2:" + str_2);
        System.out.println("str == str_2:" + str == str_2);

        System.out.println("str_3:" + str_3);
        System.out.println("str == str_3:" + str == str_3);

        System.out.println("str_4:" + str_4);
        System.out.println("str == str_4:" + str == str_4);
    }

    static void test2(){//false
        String str = new String("123");
        String str_2 = new String("123");
        System.out.println( str == str_2);
    }

    static void test3(){//false
        String str =  "123";
        String str_2 = new String("123");
        System.out.println( str == str_2);
    }

    static void test4(){//true
        String str =  "123";
        String str_2 = "123";
        System.out.println( str == str_2);
    }    

    public static void main(String[] args) {
        test2();
        test3();
        test4();

    }

}

总结：new 一定是深拷贝，好要继续实验