Problems

1) Inspect all the properties of equals method:

package certification.collections;

class WrongMoney {

}

class Money extends Object {
	private int id;
	private String currency;

	public Money(int id, String currency) {
		super();
		this.id = id;
		this.currency = currency;
	}

	public int getId() {
		return id;
	}

	public void setId(int id) {
		this.id = id;
	}

	public String getCurrency() {
		return currency;
	}

	public void setCurrency(String currency) {
		this.currency = currency;
	}

	public boolean equals(Object obj) {
		if (this == obj) {
			return true;
		}
		if (null != obj) {
			if (obj instanceof Money) {
				Money money = (Money) obj;
				if (this.getId() == money.getId() && this.getCurrency().equals(money.getCurrency())) {
					return true;
				} else {
					return false;
				}
			} else {
				return false;
			}
		} else {
			return false;
		}
	}

}

public class TestEquals {

	public static void main(String[] args) {

		Money m1 = new Money(1, "INR");
		Money m2 = new Money(1, "INR");
		Money m3 = new Money(1, "INR");

		WrongMoney wrongMoney = new WrongMoney();

		if (m1.equals(m2)) {
			System.out.println("They are same");
		} else {
			System.out.println("Not same");
		}

		if (m1.equals(wrongMoney)) {
			System.out.println("They are same");
		} else {
			System.out.println("Not same");
		}

		if (m1.equals(m1)) {
			System.out.println("my equals is reflexive");
		}
		if (m1.equals(m2) && m2.equals(m1)) {
			System.out.println("my equals is symmetric");
		}
		if (m1.equals(m2) && m2.equals(m3)) {
			if (m1.equals(m3)) {
				System.out.println("my equals is transitive");
			}
		}

	}

}