Period.java

// Broken "immutable" time period class - Page 184
package org.effectivejava.examples.chapter07.item39;

import java.util.Date;

public final class Period {
	private final Date start;
	private final 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) {
		if (start.compareTo(end) > 0)
			throw new IllegalArgumentException(start + " after " + end);
		this.start = start;
		this.end = end;
	}

	// Repaired constructor - makes defensive copies of parameters - Page 185
	// Stops first attack
	// 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 start;
	}

	public Date end() {
		return end;
	}

	// Repaired accessors - make defensive copies of internal fields - Page 186
	// Stops second attack
	// public Date start() {
	// return new Date(start.getTime());
	// }
	//
	// public Date end() {
	// return new Date(end.getTime());
	// }

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

	// Remainder omitted
}