.equals ==

public class StringDemo {
    public static void main(String[] args) {
        String str1 = "hello";
        String str5=str1;
        String str6 = "hello";
        String str2 = null;
        String str3 = null;
        System.out.println(str1.equals(str5));
        System.out.println(str1==str5);
        System.out.println(str1.equals(str6));
        System.out.println(str1==str6);
        System.out.println(str2==str3);



        String s1,s2,s3="abc",s4="abc";
        s1=new String("abc");
        s2=new String("abc");
        System.out.println(s1==s2);   //两个变量的内存地址不一样(他们指向的对象不一样)
        System.out.println(s1.equals(s2));   //两个变量所包含的内容是abc
        
    }
}

public class StringDemo {
    public static void main(String[] args) {
        StringDemo obj1=new StringDemo();
        StringDemo obj2=new StringDemo();
        System.out.println(obj1==obj2);
        System.out.println(obj1.equals(obj2));

       /* StringDemo obj1=new StringDemo();
        StringDemo obj2=new StringDemo();
        obj1=obj2;
        System.out.println(obj1==obj2);
        System.out.println(obj1.equals(obj2));*/


    }
}

public class StringDemo {
    public static void main(String[] args) {
       /* StringDemo obj1=new StringDemo();
        StringDemo obj2=new StringDemo();
        System.out.println(obj1==obj2);
        System.out.println(obj1.equals(obj2));*/

        StringDemo obj1=new StringDemo();
        StringDemo obj2=new StringDemo();
        obj1=obj2;
        System.out.println(obj1==obj2);
        System.out.println(obj1.equals(obj2));


    }
}

public class StringDemo {
    public static void main(String[] args) {
      
        String str1 = new String("hello");
        String str2 = new String("hello");
        System.out.println(str1==str2);
        System.out.println(str1.equals(str2));
    }
}