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Java example source code file (

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Java - Java tags/keywords

comparable, immutablepair, object, override, pair, serializable, string, suppresswarnings, util

The Java example source code

 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * See the License for the specific language governing permissions and
 * limitations under the License.
package org.apache.commons.lang3.tuple;

import java.util.Map;

import org.apache.commons.lang3.ObjectUtils;
import org.apache.commons.lang3.builder.CompareToBuilder;

 * <p>A pair consisting of two elements.

* * <p>This class is an abstract implementation defining the basic API. * It refers to the elements as 'left' and 'right'. It also implements the * {@code Map.Entry} interface where the key is 'left' and the value is 'right'.</p> * * <p>Subclass implementations may be mutable or immutable. * However, there is no restriction on the type of the stored objects that may be stored. * If mutable objects are stored in the pair, then the pair itself effectively becomes mutable.</p> * * @param <L> the left element type * @param <R> the right element type * * @since Lang 3.0 */ public abstract class Pair<L, R> implements Map.Entry, Comparable>, Serializable { /** Serialization version */ private static final long serialVersionUID = 4954918890077093841L; /** * <p>Obtains an immutable pair of from two objects inferring the generic types.

* * <p>This factory allows the pair to be created using inference to * obtain the generic types.</p> * * @param <L> the left element type * @param <R> the right element type * @param left the left element, may be null * @param right the right element, may be null * @return a pair formed from the two parameters, not null */ public static <L, R> Pair of(final L left, final R right) { return new ImmutablePair<L, R>(left, right); } //----------------------------------------------------------------------- /** * <p>Gets the left element from this pair.

* * <p>When treated as a key-value pair, this is the key.

* * @return the left element, may be null */ public abstract L getLeft(); /** * <p>Gets the right element from this pair.

* * <p>When treated as a key-value pair, this is the value.

* * @return the right element, may be null */ public abstract R getRight(); /** * <p>Gets the key from this pair.

* * <p>This method implements the {@code Map.Entry} interface returning the * left element as the key.</p> * * @return the left element as the key, may be null */ @Override public final L getKey() { return getLeft(); } /** * <p>Gets the value from this pair.

* * <p>This method implements the {@code Map.Entry} interface returning the * right element as the value.</p> * * @return the right element as the value, may be null */ @Override public R getValue() { return getRight(); } //----------------------------------------------------------------------- /** * <p>Compares the pair based on the left element followed by the right element. * The types must be {@code Comparable}.</p> * * @param other the other pair, not null * @return negative if this is less, zero if equal, positive if greater */ @Override public int compareTo(final Pair<L, R> other) { return new CompareToBuilder().append(getLeft(), other.getLeft()) .append(getRight(), other.getRight()).toComparison(); } /** * <p>Compares this pair to another based on the two elements.

* * @param obj the object to compare to, null returns false * @return true if the elements of the pair are equal */ @SuppressWarnings( "deprecation" ) // ObjectUtils.equals(Object, Object) has been deprecated in 3.2 @Override public boolean equals(final Object obj) { if (obj == this) { return true; } if (obj instanceof Map.Entry<?, ?>) { final Map.Entry<?, ?> other = (Map.Entry) obj; return ObjectUtils.equals(getKey(), other.getKey()) && ObjectUtils.equals(getValue(), other.getValue()); } return false; } /** * <p>Returns a suitable hash code. * The hash code follows the definition in {@code Map.Entry}.</p> * * @return the hash code */ @Override public int hashCode() { // see Map.Entry API specification return (getKey() == null ? 0 : getKey().hashCode()) ^ (getValue() == null ? 0 : getValue().hashCode()); } /** * <p>Returns a String representation of this pair using the format {@code ($left,$right)}.

* * @return a string describing this object, not null */ @Override public String toString() { return new StringBuilder().append('(').append(getLeft()).append(',').append(getRight()).append(')').toString(); } /** * <p>Formats the receiver using the given format.

* * <p>This uses {@link java.util.Formattable} to perform the formatting. Two variables may * be used to embed the left and right elements. Use {@code %1$s} for the left * element (key) and {@code %2$s} for the right element (value). * The default format used by {@code toString()} is {@code (%1$s,%2$s)}.</p> * * @param format the format string, optionally containing {@code %1$s} and {@code %2$s}, not null * @return the formatted string, not null */ public String toString(final String format) { return String.format(format, getLeft(), getRight()); } }

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