Assert.java

/*
 * Copyright 2012 Daniel Bechler
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package de.danielbechler.util;

import java.util.Collection;

/** @author Daniel Bechler */
public class Assert
{
	private Assert()
	{
	}

	public static void equalTypesOrNull(final Object... objects)
	{
		final Collection<Class<?>> types = Classes.typesOf(objects);
		Class<?> previousType = null;
		for (final Class<?> type : types)
		{
			if (previousType != null && !type.equals(previousType))
			{
				throw new IllegalArgumentException("The given objects should be either null or of the same type ('" + previousType + "') = " + types);
			}
			previousType = type;
		}
	}

	public static void notNull(final Object object, final String name)
	{
		if (object == null)
		{
			throw new IllegalArgumentException("'" + name + "' must not be null");
		}
	}

	public static void notEmpty(final Collection<?> collection, final String name)
	{
		if (Collections.isEmpty(collection))
		{
			throw new IllegalArgumentException("'" + name + "' must not be null or empty");
		}
	}

	/**
	 * Same as {@link #hasText(String, String)}.
	 *
	 * @see #hasText(String, String)
	 */
	public static void notEmpty(final String text, final String name) throws IllegalArgumentException
	{
		hasText(text, name);
	}

	/**
	 * Ensures that the given <code>value</code> contains characters.
	 *
	 * @param value The value to check.
	 * @param name  The name of the variable (used for the exception message).
	 *
	 * @throws IllegalArgumentException If the given value is <code>null</code> or doesn't contain any non-whitespace
	 *                                  characters.
	 */
	public static void hasText(final String value, final String name) throws IllegalArgumentException
	{
		if (Strings.isEmpty(name)) // Yo dawg, I heard you like assertions, so I put an assertion in your assertion
		{
			throw new IllegalArgumentException("'name' must not be null or empty");
		}
		if (Strings.isEmpty(value))
		{
			throw new IllegalArgumentException("'" + name + "' must not be null or empty");
		}
	}
}