| /* |
| * 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. |
| */ |
| |
| package org.apache.wayang.core.util; |
| |
| import java.util.HashMap; |
| import java.util.Iterator; |
| import java.util.Map; |
| import java.util.Objects; |
| |
| /** |
| * This utility helps to count elements. |
| */ |
| public class Counter<T> implements Iterable<Map.Entry<T, Integer>> { |
| |
| private final Map<T, Integer> counts = new HashMap<>(); |
| |
| public int get(T element) { |
| return this.counts.getOrDefault(element, 0); |
| } |
| |
| /** |
| * Counts the given {@code delta} for the given {@code element}. |
| * @return the new count |
| */ |
| public int add(T element, int delta) { |
| final int currentCount = this.get(element); |
| final int newCount = currentCount + delta; |
| if (newCount == 0) { |
| this.counts.remove(element); |
| } else { |
| this.counts.put(element, newCount); |
| } |
| |
| return newCount; |
| } |
| |
| public int increment(T element) { |
| return this.add(element, 1); |
| } |
| |
| public int decrement(T element) { |
| return this.add(element, -1); |
| } |
| |
| public void addAll(Counter<T> that) { |
| this.addAll(that.counts); |
| } |
| |
| private void addAll(Map<T, Integer> counts) { |
| counts.entrySet().forEach(count -> this.add(count.getKey(), count.getValue())); |
| } |
| |
| public boolean isEmpty() { |
| return this.counts.isEmpty(); |
| } |
| |
| @Override |
| public boolean equals(Object o) { |
| if (this == o) return true; |
| if (o == null || this.getClass() != o.getClass()) return false; |
| Counter<?> counter = (Counter<?>) o; |
| return Objects.equals(this.counts, counter.counts); |
| } |
| |
| @Override |
| public int hashCode() { |
| return Objects.hash(this.counts); |
| } |
| |
| @Override |
| public Iterator<Map.Entry<T, Integer>> iterator() { |
| return this.counts.entrySet().iterator(); |
| } |
| |
| public void remove(T element) { |
| this.counts.remove(element); |
| } |
| |
| public void clear() { |
| this.counts.clear(); |
| } |
| } |