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/*
* Copyright (c) 2010, 2018 Oracle and/or its affiliates. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v. 2.0, which is available at
* http://www.eclipse.org/legal/epl-2.0.
*
* This Source Code may also be made available under the following Secondary
* Licenses when the conditions for such availability set forth in the
* Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
* version 2 with the GNU Classpath Exception, which is available at
* https://www.gnu.org/software/classpath/license.html.
*
* SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
*/
package org.glassfish.jersey.internal.util.collection;
/**
* A collection of {@link Ref reference} factory & utility methods.
*
* @author Marek Potociar (marek.potociar at oracle.com)
*/
public final class Refs {
private Refs() {
// preventing instantiation
}
/**
* Immutable {@link Ref} implementation.
*/
private static final class ImmutableRefImpl implements Ref {
private final T reference;
ImmutableRefImpl(final T value) {
this.reference = value;
}
@Override
public T get() {
return reference;
}
@Override
public void set(final T value) throws IllegalStateException {
throw new IllegalStateException("This implementation of Ref interface is immutable.");
}
@Override
public String toString() {
return "ImmutableRefImpl{"
+ "reference=" + reference
+ '}';
}
@Override
public boolean equals(final Object obj) {
if (obj == null) {
return false;
}
if (!(obj instanceof Ref)) {
return false;
}
Object otherRef = ((Ref) obj).get();
return this.reference == otherRef || (this.reference != null && this.reference.equals(otherRef));
}
@Override
public int hashCode() {
int hash = 5;
hash = 47 * hash + (this.reference != null ? this.reference.hashCode() : 0);
return hash;
}
}
/**
* Default (mutable) {@link Ref} implementation. This implementation is not thread-safe.
*/
private static final class DefaultRefImpl implements Ref {
private T reference;
DefaultRefImpl() {
this.reference = null;
}
DefaultRefImpl(final T value) {
this.reference = value;
}
@Override
public T get() {
return reference;
}
@Override
public void set(final T value) throws IllegalStateException {
this.reference = value;
}
@Override
public String toString() {
return "DefaultRefImpl{"
+ "reference=" + reference
+ '}';
}
@Override
public boolean equals(final Object obj) {
if (obj == null) {
return false;
}
if (!(obj instanceof Ref)) {
return false;
}
Object otherRef = ((Ref) obj).get();
T ref = this.reference;
return ref == otherRef || (ref != null && ref.equals(otherRef));
}
@Override
public int hashCode() {
int hash = 5;
hash = 47 * hash + (this.reference != null ? this.reference.hashCode() : 0);
return hash;
}
}
/**
* Thread-safe {@link Ref} implementation.
*/
private static final class ThreadSafeRefImpl implements Ref {
private volatile T reference;
ThreadSafeRefImpl() {
this.reference = null;
}
ThreadSafeRefImpl(final T value) {
this.reference = value;
}
@Override
public T get() {
return reference;
}
@Override
public void set(final T value) throws IllegalStateException {
this.reference = value;
}
@Override
public String toString() {
return "ThreadSafeRefImpl{"
+ "reference=" + reference
+ '}';
}
@Override
public boolean equals(final Object obj) {
if (obj == null) {
return false;
}
if (!(obj instanceof Ref)) {
return false;
}
Object otherRef = ((Ref) obj).get();
T localRef = this.reference;
return localRef == otherRef || (localRef != null && localRef.equals(otherRef));
}
@Override
public int hashCode() {
T localRef = this.reference;
int hash = 5;
hash = 47 * hash + (localRef != null ? localRef.hashCode() : 0);
return hash;
}
}
/**
* Construct a new mutable {@link Ref} instance referencing the given
* input value.
*
* @param type of the referenced instance.
* @param value value of the newly constructed reference.
* @return a new mutable {@link Ref} instance referencing the given
* input value.
*/
public static Ref of(final T value) {
return new DefaultRefImpl(value);
}
/**
* Construct a new empty mutable {@link Ref} instance.
*
* @param type of the referenced instance.
* @return a new mutable empty {@link Ref} instance.
*/
public static Ref emptyRef() {
return new DefaultRefImpl();
}
/**
* Construct a new empty mutable thread-safe {@link Ref} instance.
*
* @param type of the referenced instance.
* @return a new mutable empty thread-safe {@link Ref} instance.
* @since 2.8
*/
public static Ref threadSafe() {
return new ThreadSafeRefImpl();
}
/**
* Construct a new mutable thread-safe {@link Ref} instance referencing the given
* input value.
*
* @param type of the referenced instance.
* @param value value of the newly constructed reference.
* @return a new mutable thread-safe {@link Ref} instance referencing the given
* input value.
* @since 2.8
*/
public static Ref threadSafe(final T value) {
return new ThreadSafeRefImpl(value);
}
/**
* Construct a new immutable {@link Ref} instance referencing the given
* input value.
*
* Invoking a {@link Ref#set(java.lang.Object)} on the returned instance
* will result in a {@link IllegalStateException} being thrown.
*
* @param type of the referenced instance.
* @param value value of the newly constructed reference.
* @return a new immutable {@link Ref} instance referencing the given
* input value.
*/
public static Ref immutableRef(final T value) {
return new ImmutableRefImpl(value);
}
}