dart/editor/tools/plugins/org.eclipse.wst.sse.ui/src/org/eclipse/wst/sse/ui/internal/util/Assert.java

/*******************************************************************************
 * Copyright (c) 2001, 2005 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 Jens Lukowski/Innoopract - initial renaming/restructuring
 *******************************************************************************/
package org.eclipse.wst.sse.ui.internal.util;

/**
 * <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 being catching them specifically).
 * </p>
 */
public final class Assert {

  /**
   * <code>AssertionFailedException</code> is a runtime exception thrown by some of the methods in
   * <code>Assert</code>.
   * <p>
   * This class is not declared public to prevent some misuses; programs that catch or otherwise
   * depend on assertion failures are susceptible to unexpected breakage when assertions in the code
   * are added or removed.
   * </p>
   */
  class AssertionFailedException extends RuntimeException {
    /**
     * Comment for <code>serialVersionUID</code>
     */
    private static final long serialVersionUID = 1L;

    /**
     * Constructs a new exception.
     */
    public AssertionFailedException() {
      super();
    }

    /**
     * Constructs a new exception with the given message.
     */
    public AssertionFailedException(String detail) {
      super(detail);
    }
  }

  /**
   * 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 outcode 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. 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
   * @exception IllegalArgumentException if the object is <code>null</code>
   */
  public static void isNotNull(Object object, String message) {
    if (object == null) {
      throw new Assert().new AssertionFailedException(message);
    }
  }

  /**
   * 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 outcode 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) {
    if (!expression) {
      throw new Assert().new AssertionFailedException(message);
    }
    return expression;
  }

  /* This class is not intended to be instantiated. */
  private Assert() {
  }
}