StaticObject.java
/*
* Java Genetic Algorithm Library (@__identifier__@).
* Copyright (c) @__year__@ Franz Wilhelmstötter
*
* 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.
*
* Author:
* Franz Wilhelmstötter (franz.wilhelmstoetter@gmx.at)
*/
package org.jenetics.util;
import static java.lang.String.format;
/**
* This class is used to <i>tag</i> a class as <i>object</i> with static
* methods only. Such classes are not supposed to be treated as <i>types</i>.
* The protected constructor always throws an {@link AssertionError} and
* prevents the <i>static object</i> from being instantiated.
*
* The following <i>pattern</i> is used for creating such static helper
* classes—the only constructors is declared private to gain the wished
* compile-time safety:
* [code]
* public final class utils extends StaticObject {
* private utils() {}
*
* ...
* }
* [/code]
*
* By convention, {@code StaticObject} names are all lower-case in this library.
*
* @author <a href="mailto:franz.wilhelmstoetter@gmx.at">Franz Wilhelmstötter</a>
* @since 1.1
* @version 1.1 — <em>$Date: 2013-09-01 $</em>
*/
public abstract class StaticObject {
/**
* Calling the constructor of an {@code StaticObject} will always throw an
* {@link AssertionError}.
*
* @throws AssertionError always.
*/
protected StaticObject() {
String message = "Object instantiation is not allowed";
final StackTraceElement[] trace = Thread.currentThread().getStackTrace();
if (trace.length >= 3) {
message = format(
"Instantiation of '%s' is not allowed.",
trace[2].getClassName()
);
}
throw new AssertionError(message);
}
}