Java Tech - Chapter 3

The example below illustrates the two different ways to instantiate a class that contains two constructors. A class can possess any number of constructors and thus allow great flexiblity in the initialization of an instance of that class. (In Chapter 4 we discuss this technique of overloading constructors and methods.)

ConstructorsApplet.java
(Output goes to browser's Java console.)

public class ConstructorsApplet extends java.applet.Applet
{
  public void init () {
    // Create an instance of the Test class using
    // its no argument constructor.
    Test test = new Test ();

    // Here a new Test object is created using
    // its one argument constructor.
    test = new Test (i);
  }

  // Paint message in Applet window.
  public void paint (java.awt.Graphics g) {
  g.drawString ("ConstructorsApplet", 10, 20);
}
}

// This Test class has two constructors.
class Test
{
  Test () {
    System.out.println ("In Test ()");
    System.out.println ("m = " + m);
    System.out.println ();
  }

  // Note that placement of a data field in the class
  // definition is not important
  int m;
  Test (int j) {
    m = j;
    System.out.println ("In Test (int j)");
    System.out.println ("m = " + m);
    System.out.println ();
  }
}

Application version:
ConstructorsApp.java