Here i wrote small code  to test the different between equals and "=="
public class TestString {
    public static void main(String[] args){
        String s = "Hello World";
        String s1 = new String("Hello World");
        String s2 =s.intern();
        String s3 = "Hello World";

        System.out.println("s == s1: " + (s==s1));
        System.out.println("s == s2: " + (s==s2));
        System.out.println("s == s3: " + (s==s3));

        System.out.println("s equal s1: " + s.equals(s1));
        System.out.println("s == s1: " + s1.intern()==s.intern());

        }
}

However, I got some strange output as follows:
s == s1: false
s == s2: true
s == s3: true
false

For the last output s==s1 is missed. Does anyone have some idea about
this?

Thanks