Programming with Constructors in Java

The explanation for the code in this section was given in the previous section.  Now, open your previous application (or download it from my previous articles) and open “MyCalc.java.”  Modify your code so that it looks something like the following:

  public class MyCalc {

    int x;
    int y;

    public MyCalc() {
        x = 10;
        y = 10;
    }

    public MyCalc(int m, int n) {
        x=m;
        y=n;
    }

    public void setValues(int m, int n) {
        x = m;
        y = n;
    }

   
    public int getSum() {
        int z;
        z = x + y;
        return z;
    }

  }

In the above class, I simply included two constructors. But you are free to include any number of constructors, as long as there exists some difference in the parameters.  You can also include a constructor which accepts an object as a parameter as follows:

    public MyCalc(MyCalc c) {
        x=c.x;
        y=c.y;
    }

In fact, you can also pass arrays as parameters (including arrays of objects).  It is simply your choice. Now, go back to the frame “test.java.” Double click on it to open and finally double click on the button to open source view.  Within the source view, modify your “buttonActionPerformed” in such a way that it looks like the following:

  private void btnShowActionPerformed(java.awt.event.ActionEvent evt) {
  // TODO add your handling code here:
        MyCalc obj1 = new MyCalc();
        MyCalc obj2 = new MyCalc(10,20);
        int r;
        r = obj1.getSum();
        this.lblMsg.setText("Sum = " + String.valueOf(r));
        r = obj2.getSum();
        this.lblMsg2.setText("Sum = " + String.valueOf(r));

    }

The entire code for this article is freely available in the form of a zip file.  That downloadable solution was developed using NetBeans 4.1 IDE together with Microsoft Windows 2003 Standard Edition. I didn’t really test it in any other version or platform. Please follow the respective platform documentation to get it worked. This series is dedicated to the beginners who wanted to work with NetBeans IDE.

Any doubts, bugs, errors, suggestions, feedback etc. are highly appreciated at jag_chat@yahoo.com.