Integer vs int in java

Is there anything interesting between them.

If you are a Junior Java developer then maybe it is fun.
If you are a Senior Java developer then maybe it is also funny for you
If you are a Profesional Java Developer then maybe it is not excited

Anyone try to run this block code

public static void main(String[] args) {

        Integer x = new Integer(1);

        int y = 1;

        if (x == y) {

            System.out.println(true);

        } else {

            System.out.println(false);

        }

}              

---> It is clearly: true

public static void main(String[] args) {

        Integer x = 100;

        Integer y = 100;

        if (x == y) {

            System.out.println(true);

        } else {

            System.out.println(false);

        }

    }

--> It is still true

public static void main(String[] args) {

        Integer x = 300;

        Integer y = 300;

        if (x == y) {

            System.out.println(true);

        } else {

            System.out.println(false);

        }

    }

-> It is still true ??????  No, It is false. If you dont belive You can run it online
https://www.jdoodle.com/online-java-compiler



So what happened ????

All you need to remember that

You have a Integer Box that contains {-128 ,-127, -126, ..., 0, ... , 125, 126, 127}

So when you use this command:
Integer x= 123; 

Because          -128      =<       123       <=         127
It will search in Integer Box and return the memory address of that value

Integer y = 123;

It return the same memory address of 123

So  x == y return TRUE because x and y were the same memory address

-----------------------------------
If you code

Integer x= 128;
Integer y=128;

128 is not in Integer Box

Then x and y has different memory address. Then x == y will return false

----------------------------------

Integer x = new Integer(123);  --> new heap memory address
Integer y =123;  -> Integer Box memory address

Then x==y return false
----------------------------------

Integer x= 300;
int y =300;

Then x == y return true; Because x will be cast to int value, and they will compare the same value of 300

-------------------------------
Integer x = new Integer(100);     a new heap address memory
Integer y = new Integer(100);      another new heap address memory

then x == y return false. Because It compare the address in heap memory