1 package org.eclipse.aether.internal.impl.collect; 2 3 /* 4 * Licensed to the Apache Software Foundation (ASF) under one 5 * or more contributor license agreements. See the NOTICE file 6 * distributed with this work for additional information 7 * regarding copyright ownership. The ASF licenses this file 8 * to you under the Apache License, Version 2.0 (the 9 * "License"); you may not use this file except in compliance 10 * with the License. You may obtain a copy of the License at 11 * 12 * http://www.apache.org/licenses/LICENSE-2.0 13 * 14 * Unless required by applicable law or agreed to in writing, 15 * software distributed under the License is distributed on an 16 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 17 * KIND, either express or implied. See the License for the 18 * specific language governing permissions and limitations 19 * under the License. 20 */ 21 22 import java.lang.ref.Reference; 23 import java.lang.ref.WeakReference; 24 import java.util.Map; 25 import java.util.WeakHashMap; 26 27 /** 28 * Pool of immutable object instances, used to avoid excessive memory consumption of (dirty) dependency graph which 29 * tends to have many duplicate artifacts/dependencies. 30 */ 31 class ObjectPool<T> 32 { 33 34 private final Map<Object, Reference<T>> objects = new WeakHashMap<>( 256 ); 35 36 public synchronized T intern( T object ) 37 { 38 Reference<T> pooledRef = objects.get( object ); 39 if ( pooledRef != null ) 40 { 41 T pooled = pooledRef.get(); 42 if ( pooled != null ) 43 { 44 return pooled; 45 } 46 } 47 48 objects.put( object, new WeakReference<>( object ) ); 49 return object; 50 } 51 52 }