Overloaded Methods

Here's an example that shows how methods can be overloaded.

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package org.megha.blog.example.part4;

import org.megha.blog.example.part2.Circle;
import org.megha.blog.example.part3.Person;

/**
 * A printer that can print a {@link Circle} or a {@link Person} or both.
 */
public class Printer {

	public void print(Circle circle) {
		System.out.println("printing circle...");
		circle.print();
	}

	public void print(Person person) {
		System.out.println("printing person...");
		person.print();
	}

	public void print(Circle circle, Person person) {
		System.out.println("printing circle and person");
		person.print();
		circle.print();
	}

	public void print(Person person, Circle circle) {
		System.out.println("printing person and circle");
		person.print();
		circle.print();
	}

	public static void main(String args[]) {

		Printer printer = new Printer();

		Circle circle1 = new Circle(8);
		Person person1 = new Person("Samuel", "Engineer");

		printer.print(circle1);
		printer.print(person1);
		printer.print(circle1, person1);
		printer.print(person1, circle1);
	}
}

Overloaded Constructors

Here's how we can overload constructors - and use any one of them at create time.

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package org.megha.blog.example.part3;

/**
 * Represents a person, with a name and a title.
 */
public class Person {

	private String name;
	private String title;

	/** creates a {@link Person} with a name and a title */
	public Person(String name, String title) {
		this.name = name;
		this.title = title;
	}

	/** creates a {@link Person} with only a name (title is set to UNKNOWN) */
	public Person(String name) {
		this(name, "UNKNOWN"); // calls the previous constructor
                                       // with title as UNKNOWN
	}

	/** creates a {@link Person} without a name or a title */
	public Person() {
		this("NO_NAME"); 
                // note how the one-arg constructor is called, 
                // which calls the two arg constructor
	}

	public void print() {
		System.out.println("----------------------");
		System.out.println("Name = " + name);
		System.out.println("Title = " + title);
	}

	public static void main(String args[]) {
		// Person class has overloaded constructors,
                // and we can call any of these.
		Person person1 = new Person();
		Person person2 = new Person("Sam");
		Person person3 = new Person("Sam","Engineer");

		person1.print();
		person2.print();
		person3.print();
	}
}

Output of this program:

----------------------
Name = NO_NAME
Title = UNKNOWN
----------------------
Name = Sam
Title = UNKNOWN
----------------------
Name = Sam
Title = Engineer