Assert.java

/*******************************************************************************
 * Copyright (c) 2000, 2009 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 * 
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.core.runtime;

/**
 * <code>Assert</code> is useful for for embedding runtime sanity checks in
 * code. The predicate methods all test a condition and throw some type of
 * unchecked exception if the condition does not hold.
 * <p>
 * Assertion failure exceptions, like most runtime exceptions, are thrown when
 * something is misbehaving. Assertion failures are invariably unspecified
 * behavior; consequently, clients should never rely on these being thrown (and
 * certainly should not be catching them specifically).
 * </p>
 * <p>
 * This class can be used without OSGi running.
 * </p>
 * <p>
 * This class is not intended to be instantiated or sub-classed by clients.
 * </p>
 * 
 * @since org.eclipse.equinox.common 3.2
 * @noinstantiate This class is not intended to be instantiated by clients.
 */
public final class Assert {
	/* This class is not intended to be instantiated. */
	private Assert() {
		// not allowed
	}

	/**
	 * Asserts that an argument is legal. If the given boolean is not
	 * <code>true</code>, an <code>IllegalArgumentException</code> is thrown.
	 * 
	 * @param expression
	 *            the outcome of the check
	 * @return <code>true</code> if the check passes (does not return if the
	 *         check fails)
	 * @exception IllegalArgumentException
	 *                if the legality test failed
	 */
	public static boolean isLegal(boolean expression) {
		return isLegal(expression, ""); //$NON-NLS-1$
	}

	/**
	 * Asserts that an argument is legal. If the given boolean is not
	 * <code>true</code>, an <code>IllegalArgumentException</code> is thrown.
	 * The given message is included in that exception, to aid debugging.
	 * 
	 * @param expression
	 *            the outcome of the check
	 * @param message
	 *            the message to include in the exception
	 * @return <code>true</code> if the check passes (does not return if the
	 *         check fails)
	 * @exception IllegalArgumentException
	 *                if the legality test failed
	 */
	public static boolean isLegal(boolean expression, String message) {
		if (!expression)
			throw new IllegalArgumentException(message);
		return expression;
	}

	/**
	 * Asserts that the given object is not <code>null</code>. If this is not
	 * the case, some kind of unchecked exception is thrown.
	 * 
	 * @param object
	 *            the value to test
	 */
	public static void isNotNull(Object object) {
		isNotNull(object, ""); //$NON-NLS-1$
	}

	/**
	 * Asserts that the given object is not <code>null</code>. If this is not
	 * the case, some kind of unchecked exception is thrown. The given message
	 * is included in that exception, to aid debugging.
	 * 
	 * @param object
	 *            the value to test
	 * @param message
	 *            the message to include in the exception
	 */
	public static void isNotNull(Object object, String message) {
	}

	/**
	 * Asserts that the given boolean is <code>true</code>. If this is not the
	 * case, some kind of unchecked exception is thrown.
	 * 
	 * @param expression
	 *            the outcome of the check
	 * @return <code>true</code> if the check passes (does not return if the
	 *         check fails)
	 */
	public static boolean isTrue(boolean expression) {
		return isTrue(expression, ""); //$NON-NLS-1$
	}

	/**
	 * Asserts that the given boolean is <code>true</code>. If this is not the
	 * case, some kind of unchecked exception is thrown. The given message is
	 * included in that exception, to aid debugging.
	 * 
	 * @param expression
	 *            the outcome of the check
	 * @param message
	 *            the message to include in the exception
	 * @return <code>true</code> if the check passes (does not return if the
	 *         check fails)
	 */
	public static boolean isTrue(boolean expression, String message) {
		return expression;
	}
}