api/src/main/java/org/apache/commons/graph/utils/Assertions.java

package org.apache.commons.graph.utils;

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.
 */

import static java.lang.String.format;

/**
 * Code partially extracted from Google Collections
 */
public final class Assertions
{

    private Assertions()
    {
        // do nothing
    }

    /**
     * Ensures the truth of an expression involving one or more parameters to the
     * calling method.
     *
     * @param expression a boolean expression
     * @param errorMessageTemplate a template for the exception message should the
     *     check fail. The message is formed by replacing each {@code %s}
     *     placeholder in the template with an argument. These are matched by
     *     position - the first {@code %s} gets {@code errorMessageArgs[0]}, etc.
     *     Unmatched arguments will be appended to the formatted message in square
     *     braces. Unmatched placeholders will be left as-is.
     * @param errorMessageArgs the arguments to be substituted into the message
     *     template. Arguments are converted to strings using
     *     {@link String#valueOf(Object)}.
     * @throws IllegalArgumentException if {@code expression} is false
     * @throws NullPointerException if the check fails and either {@code
     *     errorMessageTemplate} or {@code errorMessageArgs} is null (don't let
     *     this happen)
     */
    public static void checkArgument( boolean expression, String errorMessageTemplate, Object... errorMessageArgs )
    {
        if ( !expression )
        {
            throw new IllegalArgumentException( format( errorMessageTemplate, errorMessageArgs ) );
        }
    }

    /**
     * Ensures the truth of an expression involving the state of the calling
     * instance, but not involving any parameters to the calling method.
     *
     * @param expression a boolean expression
     * @param errorMessageTemplate a template for the exception message should the
     *     check fail. The message is formed by replacing each {@code %s}
     *     placeholder in the template with an argument. These are matched by
     *     position - the first {@code %s} gets {@code errorMessageArgs[0]}, etc.
     *     Unmatched arguments will be appended to the formatted message in square
     *     braces. Unmatched placeholders will be left as-is.
     * @param errorMessageArgs the arguments to be substituted into the message template.
     * @throws IllegalStateException if {@code expression} is false
     * @throws NullPointerException if the check fails and either {@code
     *     errorMessageTemplate} or {@code errorMessageArgs} is null (don't let
     *     this happen)
     */
    public static void checkState( boolean expression, String errorMessageTemplate, Object... errorMessageArgs )
    {
        if ( !expression )
        {
            throw new IllegalStateException( format( errorMessageTemplate, errorMessageArgs ) );
        }
    }

    /**
     * Ensures that an object reference passed as a parameter to the calling
     * method is not null.
     *
     * @param reference an object reference
     * @param <T> the reference type
     * @param errorMessageTemplate a template for the exception message should the
     *     check fail. The message is formed by replacing each {@code %s}
     *     placeholder in the template with an argument. These are matched by
     *     position - the first {@code %s} gets {@code errorMessageArgs[0]}, etc.
     *     Unmatched arguments will be appended to the formatted message in square
     *     braces. Unmatched placeholders will be left as-is.
     * @param errorMessageArgs the arguments to be substituted into the message
     *     template. Arguments are converted to strings using
     *     {@link String#valueOf(Object)}.
     * @return the non-null reference that was validated
     * @throws NullPointerException if {@code reference} is null
     */
    public static <T> T checkNotNull( T reference, String errorMessageTemplate, Object... errorMessageArgs )
    {
        if ( reference == null )
        {
            // If either of these parameters is null, the right thing happens anyway
            throw new NullPointerException( format( errorMessageTemplate, errorMessageArgs ) );
        }
        return reference;
    }

}