eaglercraft-1.8/sources/main/java/com/google/common/collect/Constraint.java

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2022-12-25 01:12:28 -08:00
/*
* Copyright (C) 2007 The Guava Authors
*
* 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 com.google.common.collect;
import com.google.common.annotations.GwtCompatible;
/**
* A constraint that an element must satisfy in order to be added to a
* collection. For example, {@link Constraints#notNull()}, which prevents a
* collection from including any null elements, could be implemented like this:
*
* <pre>
* {@code
*
* public Object checkElement(Object element) {
* if (element == null) {
* throw new NullPointerException();
* }
* return element;
* }}
* </pre>
*
* <p>
* In order to be effective, constraints should be deterministic; that is, they
* should not depend on state that can change (such as external state, random
* variables, and time) and should only depend on the value of the passed-in
* element. A non-deterministic constraint cannot reliably enforce that all the
* collection's elements meet the constraint, since the constraint is only
* enforced when elements are added.
*
* @author Mike Bostock
*/
@GwtCompatible
interface Constraint<E> {
/**
* Throws a suitable {@code RuntimeException} if the specified element is
* illegal. Typically this is either a {@link NullPointerException}, an
* {@link IllegalArgumentException}, or a {@link ClassCastException}, though an
* application-specific exception class may be used if appropriate.
*
* @param element the element to check
* @return the provided element
*/
E checkElement(E element);
/**
* Returns a brief human readable description of this constraint, such as "Not
* null" or "Positive number".
*/
@Override
String toString();
}