001/* -*- mode: Java; c-basic-offset: 2; indent-tabs-mode: nil; coding: utf-8-unix -*- 002 * 003 * Copyright © 2017–2019 microBean. 004 * 005 * Licensed under the Apache License, Version 2.0 (the "License"); 006 * you may not use this file except in compliance with the License. 007 * You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or 014 * implied. See the License for the specific language governing 015 * permissions and limitations under the License. 016 */ 017package org.microbean.configuration.spi; 018 019import java.util.Comparator; 020import java.util.Objects; 021 022/** 023 * An {@code abstract} {@link Arbiter} that uses a {@link Comparator} 024 * in some way. 025 * 026 * @param <T> the type of object that will be compared 027 * 028 * @author <a href="https://about.me/lairdnelson" 029 * target="_parent">Laird Nelson</a> 030 */ 031public abstract class ComparatorBasedArbiter<T> implements Arbiter { 032 033 034 /* 035 * Instance fields. 036 */ 037 038 039 /** 040 * A {@link Comparator} used by this {@link ComparatorBasedArbiter} 041 * in some way. 042 * 043 * @see #getComparator() 044 */ 045 private final Comparator<T> comparator; 046 047 048 /* 049 * Constructors. 050 */ 051 052 053 /** 054 * Creates a new {@link ComparatorBasedArbiter}. Should never be 055 * used. 056 * 057 * @see #ComparatorBasedArbiter(Comparator) 058 * 059 * @deprecated Please use the {@link 060 * #ComparatorBasedArbiter(Comparator)} constructor instead. 061 */ 062 @Deprecated 063 private ComparatorBasedArbiter() { 064 super(); 065 this.comparator = null; 066 } 067 068 /** 069 * Creates a new {@link ComparatorBasedArbiter}. 070 * 071 * @param comparator the {@link Comparator} to use; must not be 072 * {@code null} 073 * 074 * @exception NullPointerException if {@code comparator} is {@code 075 * null} 076 * 077 * @see #getComparator() 078 */ 079 protected ComparatorBasedArbiter(final Comparator<T> comparator) { 080 super(); 081 this.comparator = Objects.requireNonNull(comparator); 082 } 083 084 085 /* 086 * Instance methods. 087 */ 088 089 090 /** 091 * Returns the {@link Comparator} used by this {@link 092 * ComparatorBasedArbiter} implementation. 093 * 094 * <p>This method never returns {@code null}.</p> 095 * 096 * <p>Overrides of this method must never return {@code null}.</p> 097 * 098 * @return a non-{@code null} {@link Comparator} 099 * 100 * @see #ComparatorBasedArbiter(Comparator) 101 */ 102 protected Comparator<T> getComparator() { 103 return this.comparator; 104 } 105 106}