Java Program on Difference Between call by value and call by reference

Program 1

package dataflair;

class Abc
{
      int n;
      
      void increment(Abc M)  // reference 
      {
          M.n=700;    
      }
}
public class TestMain 
{
    public static void main(String[] args) 
    {
        int n=200;    
        Abc A=new Abc();
        System.out.println("Before Change" +A.n);  //0
        A.increment(A);  // call by refernce
        System.out.println("After Change" +A.n);  //0
        A.n=900;
        System.out.println("After Second Change" +A.n);  //0
        
    }
}