/com/in28minutes/java/object/EqualsHashCodeExamples.java

package com.in28minutes.java.object;

class Client {
	private int id;

	public Client(int id) {
		this.id = id;
	}

	@Override
	public int hashCode() {
		final int prime = 31;
		int result = 1;
		result = prime * result + id;
		return result;
	}

	@Override
	public boolean equals(Object obj) {
		if (this == obj)
			return true;
		if (obj == null)
			return false;
		if (getClass() != obj.getClass())
			return false;
		Client other = (Client) obj;
		if (id != other.id)
			return false;
		return true;
	}

}

public class EqualsHashCodeExamples {

	public static void main(String[] args) {

		// == comparison operator checks if the object references are pointing
		// to the same object. It does NOT look at the content of the object.
		Client client1 = new Client(25);
		Client client2 = new Client(25);
		Client client3 = client1;

		System.out.println(client1.equals(client2));// true
		System.out.println(client1.equals(client3));// true

	}
}

/com/in28minutes/java/object/ToStringExamples.java

package com.in28minutes.java.object;

class Animal {

	public Animal(String name, String type) {
		this.name = name;
		this.type = type;
	}

	String name;
	String type;

	public String toString() {
		return "Animal [name=" + name + ", type=" + type + "]";
	}

}

public class ToStringExamples {
	public static void main(String[] args) {
		Animal animal = new Animal("Tommy", "Dog");
		System.out.println(animal);// Animal [name=Tommy, type=Dog]
	}
}