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 * Internal helper class for collector implementations.
31 */
32 class ObjectPool<T>
33 {
34
35 private final Map<Object, Reference<T>> objects = new WeakHashMap<>( 256 );
36
37 public synchronized T intern( T object )
38 {
39 Reference<T> pooledRef = objects.get( object );
40 if ( pooledRef != null )
41 {
42 T pooled = pooledRef.get();
43 if ( pooled != null )
44 {
45 return pooled;
46 }
47 }
48
49 objects.put( object, new WeakReference<>( object ) );
50 return object;
51 }
52
53 }