org.jboss.marshalling.Pair Maven / Gradle / Ivy
/*
* JBoss, Home of Professional Open Source.
* Copyright 2014 Red Hat, Inc., and individual contributors
* as indicated by the @author tags.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.jboss.marshalling;
import java.io.ObjectInputStream;
import java.io.Serializable;
import java.io.Externalizable;
import java.io.ObjectOutput;
import java.io.IOException;
import java.io.ObjectInput;
/**
* A serializable pair of values. There is also a specified externalizer as well, to support more efficient I/O.
*
* @param the first value type
* @param the second value type
* @apiviz.exclude
*/
@Externalize(Pair.Externalizer.class)
public final class Pair implements Serializable {
private static final long serialVersionUID = 7331975617882473974L;
private final A a;
private final B b;
@SuppressWarnings({ "InstanceVariableMayNotBeInitializedByReadObject" })
private final transient int hashCode;
private static final FieldSetter setter = FieldSetter.get(Pair.class, "hashCode");
/**
* Create a new instance.
*
* @param a the first value
* @param b the second value
*/
public Pair(final A a, final B b) {
this.a = a;
this.b = b;
hashCode = hashCode(a, b);
}
/**
* Calculate the combined hash code of two objects.
*
* @param a the first object
* @param b the second object
* @return the combined hash code
*/
private static int hashCode(final Object a, final Object b) {
return (a == null ? 0 : a.hashCode()) * 1319 + (b == null ? 0 : b.hashCode());
}
/**
* Get the first value.
*
* @return the first value
*/
public A getA() {
return a;
}
/**
* Get the second value.
*
* @return the second value
*/
public B getB() {
return b;
}
/**
* Reinitialize the object and set the hash code.
*
* @param ois the object input stream
* @throws IOException if an I/O error occurs while reading the default fields
* @throws ClassNotFoundException if a class isn't found while reading the default fields
*/
private void readObject(ObjectInputStream ois) throws IOException, ClassNotFoundException {
ois.defaultReadObject();
setter.setInt(this, hashCode(a, b));
}
/**
* Return the combined hash code of the two argument objects.
*
* @return the combined hash code
*/
public int hashCode() {
return hashCode;
}
/**
* Determine if this pair equals another. A pair is equal to another pair if both members are equal.
*
* @param other the other pair
* @return {@code true} if they are equal, {@code false} otherwise
*/
public boolean equals(final Object other) {
return (other instanceof Pair) ? equals((Pair) other) : false;
}
/**
* Determine if this pair equals another. A pair is equal to another pair if both members are equal.
*
* @param other the other pair
* @return {@code true} if they are equal, {@code false} otherwise
*/
public boolean equals(final Pair other) {
if (other == null) {
return false;
}
final Object a = this.a;
final Object othera = other.a;
final Object b = this.b;
final Object otherb = other.b;
return (a == othera || a != null && a.equals(othera)) &&
(b == otherb || b != null && b.equals(otherb));
}
/**
* Get a string representation of this pair.
*
* @return the string representation
*/
public String toString() {
final StringBuilder builder = new StringBuilder();
builder.append("Pair (").append(a).append(", ").append(b).append(')');
return builder.toString();
}
/**
* Create a new instance.
*
* @param a the first value
* @param b the second value
* @param the first value type
* @param the second value type
* @return the new instance
*/
public static Pair create(A a, B b) {
return new Pair(a, b);
}
/**
* An externalizer for {@link Pair} instances.
* @apiviz.exclude
*/
public static final class Externalizer implements org.jboss.marshalling.Externalizer, Externalizable {
private static final long serialVersionUID = 930391108343329811L;
private static final Externalizer instance = new Externalizer();
/**
* Get the single instance. Though multiple instances can be created using the public constructor, only a single
* instance need be used in practice since this class maintains no internal state.
*
* @return the instance
*/
public static Externalizer getInstance() {
return instance;
}
/** {@inheritDoc} */
public void writeExternal(final Object subject, final ObjectOutput output) throws IOException {
output.writeObject(((Pair)subject).a);
output.writeObject(((Pair)subject).b);
}
/** {@inheritDoc} */
public Object createExternal(final Class subjectType, final ObjectInput input) throws IOException, ClassNotFoundException {
return create(input.readObject(), input.readObject());
}
/** {@inheritDoc} */
public void writeExternal(final ObjectOutput out) {
}
/** {@inheritDoc} */
public void readExternal(final ObjectInput in) {
}
/**
* Resolve the object to the single externalizer instance.
*
* @return the instance
*/
protected Object readResolve() {
return instance;
}
}
}