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/*
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
*
* Copyright (c) 2010-2012 Oracle and/or its affiliates. All rights reserved.
*
* The contents of this file are subject to the terms of either the GNU
* General Public License Version 2 only ("GPL") or the Common Development
* and Distribution License("CDDL") (collectively, the "License"). You
* may not use this file except in compliance with the License. You can
* obtain a copy of the License at
* http://glassfish.java.net/public/CDDL+GPL_1_1.html
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* language governing permissions and limitations under the License.
*
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* file and include the License file at packager/legal/LICENSE.txt.
*
* GPL Classpath Exception:
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* exception as provided by Oracle in the GPL Version 2 section of the License
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*
* Modifications:
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*/
package org.glassfish.jersey.internal.util.collection;
import com.google.common.base.Objects;
/**
* Utility class with methods for working with references.
*
* @author Paul Sandoz
* @author Marek Potociar (marek.potociar at oracle.com)
*/
public final class Refs {
private Refs() {
// preventing istantiation
}
/**
* Immutable {@link Ref} implementation.
*/
private static final class ImmutableRefImpl implements Ref {
private final T reference;
public 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 Objects.toStringHelper(this).add("reference", reference).toString();
}
@Override
public boolean equals(final Object obj) {
if (obj == null) {
return false;
}
if (getClass() != obj.getClass()) {
return false;
}
@SuppressWarnings("unchecked")
final ImmutableRefImpl other = (ImmutableRefImpl) obj;
return reference == other.reference || (reference != null && reference.equals(other.reference));
}
@Override
public int hashCode() {
int hash = 7;
hash = 83 * hash + (this.reference != null ? this.reference.hashCode() : 0);
return hash;
}
}
/**
* Default (mutable) {@link Ref} implementation.
*/
private static final class DefaultRefImpl implements Ref {
private T reference;
public DefaultRefImpl() {
this.reference = null;
}
public 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 Objects.toStringHelper(this).add("reference", reference).toString();
}
@Override
public boolean equals(final Object obj) {
if (obj == null) {
return false;
}
if (getClass() != obj.getClass()) {
return false;
}
@SuppressWarnings("unchecked")
final DefaultRefImpl other = (DefaultRefImpl) obj;
return reference == other.reference || (reference != null && reference.equals(other.reference));
}
@Override
public int hashCode() {
int hash = 5;
hash = 47 * hash + (this.reference != null ? this.reference.hashCode() : 0);
return hash;
}
}
/**
* Constructs a new mutable {@link Ref} instance referencing the given
* input reference.
*
* @param type of the referenced instance
* @param value reference of the newly constructed reference
*
* @return a new mutable {@link Ref} instance referencing the given
* input reference.
*
* @see #immutableRef(java.lang.Object)
* @see #emptyRef()
*/
public static Ref of(final T value) {
return new DefaultRefImpl(value);
}
/**
* Constructs a new empty mutable {@link Ref} instance.
*
* @param type of the referenced instance
* @return a new mutable empty {@link Ref} instance
*
* @see #immutableRef(java.lang.Object)
* @see #of(java.lang.Object)
*/
public static Ref emptyRef() {
return new DefaultRefImpl();
}
/**
* Constructs a new immutable {@link Ref} instance referencing the given
* input reference.
*
* 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 reference of the newly constructed reference
*
* @return a new immutable {@link Ref} instance referencing the given
* input reference.
*
* @see #emptyRef()
* @see #of(java.lang.Object)
*/
public static Ref immutableRef(final T value) {
return new ImmutableRefImpl(value);
}
}