Period.java

// Immutable class that uses defensive copying - Page 302
// This class is susceptible to several attacks!!
package org.effectivejava.examples.chapter11.item76;

import java.io.Serializable;
import java.util.Date;

public final class Period implements Serializable {
	private Date start;
	private Date end;

	/**
	 * @param start
	 *            the beginning of the period
	 * @param end
	 *            the end of the period; must not precede start
	 * @throws IllegalArgumentException
	 *             if start is after end
	 * @throws NullPointerException
	 *             if start or end is null
	 */
	public Period(Date start, Date end) {
		this.start = new Date(start.getTime());
		this.end = new Date(end.getTime());
		if (this.start.compareTo(this.end) > 0)
			throw new IllegalArgumentException(start + " after " + end);
	}

	public Date start() {
		return new Date(start.getTime());
	}

	public Date end() {
		return new Date(end.getTime());
	}

	public String toString() {
		return start + " - " + end;
	}

	// readObject method with validity checking - Page 304
	// This will defend against BogusPeriod attack but not MutablePeriod.
	// private void readObject(ObjectInputStream s)
	// throws IOException, ClassNotFoundException {
	// s.defaultReadObject();
	//
	// // Check that our invariants are satisfied
	// if (start.compareTo(end) > 0)
	// throw new InvalidObjectException(start +" after "+ end);
	// }

	// readObject method with defensive copying and validity checking - Page 306
	// This will defend against BogusPeriod and MutablePeriod attacks.
	// private void readObject(ObjectInputStream s)
	// throws IOException, ClassNotFoundException {
	// s.defaultReadObject();
	//
	// // Defensively copy our mutable components
	// start = new Date(start.getTime());
	// end = new Date(end.getTime());
	//
	// // Check that our invariants are satisfied
	// if (start.compareTo(end) > 0)
	// throw new InvalidObjectException(start +" after "+ end);
	// }
}