Working with Arrays of Objects with Java and NetBeans IDE

Creating array in Java is very easy.  Similarly, creating an object in Java is also very easy.  At the same time, creating an array of objects in Java is also easy, if and only if you remember that every object (or element) in the array needs to be instantiated separately.

Let us go through the code first.  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=0;
    int y=0;

    /** Creates a new instance of MyCalc */
    public MyCalc() {
    }

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

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

I simply removed the overloaded methods for the sake of convenience.  In fact, there exists no problem in having them as well.  Now, get 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[] ar = new MyCalc[10];

        for(int i=0;i<10;i++) {
            ar[i] = new MyCalc();
            ar[i].setValues(i*10,i*10+1);
        }

        int s=0;
        for(int i=0;i<10;i++) {
            s += ar[i].getSum();
        }

        this.lblMsg.setText("Sum = " + String.valueOf(s));
    }                                  

The next section will explain all of the above code.