Pass by value and pass by reference

 package main;

public class PassByValueAndPassByReference {

    public static void main(String[] args) {
        int i = 3;
        int[] arr = {1, 2, 3};
        
        foo(i);
        System.out.println(i);

        foo(arr);
        System.out.println(arr[0]);
    }

    public static void foo(int i) {
        i++;
    }

    public static void foo(int[] i) {
        i[0]++;
    }
}

Lakin:

package main;

public class PassByValueAndPassByReference {

    public static void main(String[] args) {
        int i = 3;
        int[] arr = {1, 2, 3};

        i = foo(i);
        System.out.println(i);

        arr = foo(arr);
        System.out.println(arr[0]);
    }

    public static int foo(int i) {
        return ++i;
    }

    public static int[] foo(int[] i) {
        i[0]++;
        return i;
    }
}

package main;

public class A {
    public int a = 5;
}
package main;

public class PassByValueAndPassByReference {

    public static void main(String[] args) {
        A a = new A();
        foo(a);
        System.out.println(a.a);
    }

    public static void foo(A aa) {
        aa.a++;
    }
}