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‎api/maven-api-model/src/main/java/org/apache/maven/api/model/DependencyPool.java

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/*
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* Licensed to the Apache Software Foundation (ASF) under one
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* or more contributor license agreements. See the NOTICE file
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* distributed with this work for additional information
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* regarding copyright ownership. The ASF licenses this file
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* to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing,
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* software distributed under the License is distributed on an
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* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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* KIND, either express or implied. See the License for the
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* specific language governing permissions and limitations
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* under the License.
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*/
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package org.apache.maven.api.model;
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import java.util.Objects;
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import java.util.function.BiPredicate;
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/**
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* Global dependency pool for automatic memory optimization.
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* <p>
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* This class provides automatic pooling of Dependency objects to reduce memory
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* consumption in large Maven projects. All Dependency instances created through
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* the Builder.build() method are automatically pooled.
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* <p>
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* The pool uses comprehensive equality comparison including all dependency fields
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* and InputLocation information to ensure correct behavior.
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* <p>
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* This class is package-protected and intended for internal use by generated model classes.
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*/
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class DependencyPool {
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private static final ObjectPool<Dependency> POOL = new ObjectPool<>();
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static {
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// Add shutdown hook to print statistics
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Runtime.getRuntime()
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.addShutdownHook(new Thread(
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() -> {
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long totalCalls = POOL.getTotalInternCalls();
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if (totalCalls > 0) {
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System.err.println("[INFO] DependencyPool Statistics: " + POOL.getStatistics());
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}
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},
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"DependencyPool-Statistics"));
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}
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/**
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* Comprehensive equality predicate for dependencies.
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* <p>
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* Compares all dependency fields including:
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* - groupId, artifactId, version, type, classifier, scope
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* - optional flag
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* - exclusions list
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* - systemPath
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* - InputLocation (for tracking where the dependency was defined)
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*/
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private static final BiPredicate<Dependency, Dependency> DEPENDENCY_EQUALITY = (dep1, dep2) -> {
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if (dep1 == dep2) {
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return true;
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}
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if (dep1 == null || dep2 == null) {
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return false;
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}
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return Objects.equals(dep1.getGroupId(), dep2.getGroupId())
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&& Objects.equals(dep1.getArtifactId(), dep2.getArtifactId())
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&& Objects.equals(dep1.getVersion(), dep2.getVersion())
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&& Objects.equals(dep1.getType(), dep2.getType())
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&& Objects.equals(dep1.getClassifier(), dep2.getClassifier())
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&& Objects.equals(dep1.getScope(), dep2.getScope())
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&& Objects.equals(dep1.getSystemPath(), dep2.getSystemPath())
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&& dep1.isOptional() == dep2.isOptional()
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&& Objects.equals(dep1.getExclusions(), dep2.getExclusions())
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&& Objects.equals(dep1.getLocation(""), dep2.getLocation(""));
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};
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/**
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* Private constructor to prevent instantiation.
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*/
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private DependencyPool() {}
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/**
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* Interns a dependency object in the global pool.
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* <p>
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* If an equivalent dependency already exists in the pool, that dependency is returned.
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* Otherwise, the provided dependency is added to the pool and returned.
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* <p>
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* This method is automatically called by Dependency.Builder.build() to provide
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* transparent memory optimization.
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*
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* @param dependency the dependency to intern
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* @return the pooled dependency (either existing or newly added)
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* @throws NullPointerException if dependency is null
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*/
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static Dependency intern(Dependency dependency) {
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return POOL.intern(dependency, DEPENDENCY_EQUALITY);
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}
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/**
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* Returns the approximate number of dependencies currently in the pool.
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* <p>
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* This method is primarily useful for monitoring and debugging purposes.
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*
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* @return the approximate size of the dependency pool
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*/
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static int size() {
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return POOL.size();
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}
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/**
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* Removes all dependencies from the pool.
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* <p>
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* This method is primarily useful for testing and cleanup purposes.
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* In normal operation, the pool should not need to be cleared as it uses
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* weak references that allow garbage collection when memory is needed.
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*/
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static void clear() {
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POOL.clear();
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}
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/**
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* Returns true if the pool contains no dependencies.
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*
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* @return true if the pool is empty, false otherwise
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*/
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static boolean isEmpty() {
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return POOL.isEmpty();
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}
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}

‎api/maven-api-model/src/main/java/org/apache/maven/api/model/ObjectPool.java

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/*
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* Licensed to the Apache Software Foundation (ASF) under one
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* or more contributor license agreements. See the NOTICE file
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* distributed with this work for additional information
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* regarding copyright ownership. The ASF licenses this file
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* to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing,
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* software distributed under the License is distributed on an
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* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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* KIND, either express or implied. See the License for the
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* specific language governing permissions and limitations
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* under the License.
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*/
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package org.apache.maven.api.model;
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import java.util.Objects;
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import java.util.concurrent.atomic.AtomicLong;
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import java.util.function.BiPredicate;
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/**
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* A thread-safe object pool for reusing objects to reduce memory consumption.
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* <p>
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* This pool is particularly useful for immutable objects that are created frequently
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* and have a high likelihood of duplication, such as InputLocation objects in Maven builds.
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* <p>
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* The pool uses a custom equality predicate to determine if two objects are equivalent,
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* allowing for flexible comparison strategies beyond the standard equals() method.
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* <p>
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* This class is package-protected and intended for internal use by generated model classes.
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*
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* @param <T> the type of objects to pool
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*/
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class ObjectPool<T> {
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private final SoftConcurrentMap<PoolKey<T>, T> pool = new SoftConcurrentMap<>();
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/**
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* Statistics tracking for monitoring pool effectiveness.
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*/
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private final AtomicLong totalInternCalls = new AtomicLong(0);
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private final AtomicLong cacheHits = new AtomicLong(0);
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/**
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* Creates a new empty object pool.
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*/
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ObjectPool() {}
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/**
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* Interns an object in the pool using a custom equality predicate.
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* <p>
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* If an equivalent object already exists in the pool, that object is returned.
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* Otherwise, the provided object is added to the pool and returned.
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*
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* @param object the object to intern
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* @param equalityPredicate predicate to test if two objects are equivalent
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* @return the pooled object (either existing or newly added)
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* @throws NullPointerException if object or equalityPredicate is null
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*/
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T intern(T object, BiPredicate<T, T> equalityPredicate) {
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Objects.requireNonNull(object, "object cannot be null");
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Objects.requireNonNull(equalityPredicate, "equalityPredicate cannot be null");
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totalInternCalls.incrementAndGet();
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PoolKey<T> key = new PoolKey<>(object, equalityPredicate);
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T existing = pool.get(key);
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if (existing != null) {
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cacheHits.incrementAndGet();
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return existing;
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}
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return pool.computeIfAbsent(key, k -> object);
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}
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/**
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* Retrieves an object from the pool if it exists.
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*
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* @param object the object to look for
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* @param equalityPredicate predicate to test if two objects are equivalent
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* @return the pooled object if it exists, null otherwise
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*/
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T getIfPresent(T object, BiPredicate<T, T> equalityPredicate) {
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if (object == null || equalityPredicate == null) {
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return null;
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}
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PoolKey<T> key = new PoolKey<>(object, equalityPredicate);
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return pool.get(key);
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}
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/**
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* Returns the approximate number of objects currently in the pool.
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*
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* @return the approximate size of the pool
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*/
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int size() {
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return pool.size();
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}
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/**
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* Removes all objects from the pool and resets statistics.
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*/
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void clear() {
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pool.clear();
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totalInternCalls.set(0);
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cacheHits.set(0);
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}
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/**
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* Returns true if the pool contains no objects.
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*
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* @return true if the pool is empty, false otherwise
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*/
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boolean isEmpty() {
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return pool.isEmpty();
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}
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/**
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* Returns the total number of intern calls made to this pool.
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* This method is primarily for monitoring and debugging purposes.
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*
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* @return the total number of intern calls
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*/
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long getTotalInternCalls() {
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return totalInternCalls.get();
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}
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/**
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* Returns the number of cache hits (objects found in pool).
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* This method is primarily for monitoring and debugging purposes.
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*
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* @return the number of cache hits
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*/
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long getCacheHits() {
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return cacheHits.get();
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}
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/**
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* Returns the cache hit ratio as a percentage.
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* This method is primarily for monitoring and debugging purposes.
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*
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* @return the cache hit ratio (0.0 to 1.0)
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*/
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double getCacheHitRatio() {
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long total = totalInternCalls.get();
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return total > 0 ? (double) cacheHits.get() / total : 0.0;
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}
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/**
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* Returns statistics about this pool.
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* This method is primarily for monitoring and debugging purposes.
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*
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* @return a string containing pool statistics
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*/
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String getStatistics() {
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long total = totalInternCalls.get();
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long hits = cacheHits.get();
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double hitRatio = total > 0 ? (double) hits / total : 0.0;
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return String.format(
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"ObjectPool[size=%d, totalCalls=%d, hits=%d, hitRatio=%.2f%%]",
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pool.size(), total, hits, hitRatio * 100);
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}
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/**
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* Returns a string representation of this pool, including its size and statistics.
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*
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* @return a string representation of this pool
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*/
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@Override
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public String toString() {
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return getStatistics();
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}
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/**
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* A wrapper class that combines an object with its equality predicate.
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* This allows us to use custom equality comparison for pooling.
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*/
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private static class PoolKey<T> {
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private final T object;
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private final BiPredicate<T, T> equalityPredicate;
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private final int hashCode;
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PoolKey(T object, BiPredicate<T, T> equalityPredicate) {
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this.object = Objects.requireNonNull(object, "object cannot be null");
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this.equalityPredicate = Objects.requireNonNull(equalityPredicate, "equalityPredicate cannot be null");
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this.hashCode = object.hashCode();
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}
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@Override
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public boolean equals(Object obj) {
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if (this == obj) {
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return true;
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}
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if (!(obj instanceof PoolKey<?> other)) {
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return false;
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}
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// Use the equality predicate to compare objects
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@SuppressWarnings("unchecked")
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PoolKey<T> otherKey = (PoolKey<T>) other;
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return equalityPredicate.test(this.object, otherKey.object);
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}
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@Override
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public int hashCode() {
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return hashCode;
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}
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@Override
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public String toString() {
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return "PoolKey{object=" + object + "}";
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}
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}
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}

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