/*
 * 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
 *
 *      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.
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package org.apache.commons.lang3.tuple;

import java.util.Map;

An immutable pair consisting of two Object elements.
Although the implementation is immutable, there is no restriction on the objects that may be stored. If mutable objects are stored in the pair, then the pair itself effectively becomes mutable. The class is also final, so a subclass can not add undesirable behavior.
#ThreadSafe# if both paired objects are thread-safe
Type parameters:
<L> – the left element type
<R> – the right element type
Since:
3.0/**
 * <p>An immutable pair consisting of two {@code Object} elements.</p>
 *
 * <p>Although the implementation is immutable, there is no restriction on the objects
 * that may be stored. If mutable objects are stored in the pair, then the pair
 * itself effectively becomes mutable. The class is also {@code final}, so a subclass
 * can not add undesirable behavior.</p>
 *
 * <p>#ThreadSafe# if both paired objects are thread-safe</p>
 *
 * @param <L> the left element type
 * @param <R> the right element type
 *
 * @since 3.0
 */
public final class ImmutablePair<L, R> extends Pair<L, R> {

    
An empty array.
 Consider using emptyArray() to avoid generics warnings. 
Since:
3.10./**
     * An empty array.
     * <p>
     * Consider using {@link #emptyArray()} to avoid generics warnings.
     * </p>
     *
     * @since 3.10.
     */
    public static final ImmutablePair<?, ?>[] EMPTY_ARRAY = new ImmutablePair[0];

    
An immutable pair of nulls.
/**
     * An immutable pair of nulls.
     */
    // This is not defined with generics to avoid warnings in call sites.
    @SuppressWarnings("rawtypes")
    private static final ImmutablePair NULL = of(null, null);

    
Serialization version /** Serialization version */
    private static final long serialVersionUID = 4954918890077093841L;

    
Returns the empty array singleton that can be assigned without compiler warning.
Type parameters:
<L> – the left element type
<R> – the right element type
Returns:
the empty array singleton that can be assigned without compiler warning.
Since:
3.10./**
     * Returns the empty array singleton that can be assigned without compiler warning.
     *
     * @param <L> the left element type
     * @param <R> the right element type
     * @return the empty array singleton that can be assigned without compiler warning.
     *
     * @since 3.10.
     */
    @SuppressWarnings("unchecked")
    public static <L, R> ImmutablePair<L, R>[] emptyArray() {
        return (ImmutablePair<L, R>[]) EMPTY_ARRAY;
    }

    
Creates an immutable pair of two objects inferring the generic types.
This factory allows the pair to be created using inference to
obtain the generic types.
Params:
left –  the left element, may be null
Type parameters:
<L> – the left element type
<R> – the right element type
Returns:
a pair formed from the two parameters, not null
Since:
3.11/**
     * <p>Creates an immutable pair of two objects inferring the generic types.</p>
     *
     * <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
     * @return a pair formed from the two parameters, not null
     * @since 3.11
     */
    public static <L, R> Pair<L, R> left(final L left) {
        return ImmutablePair.of(left, null);
    }

    
Returns an immutable pair of nulls.
Type parameters:
<L> – the left element of this pair. Value is null.
<R> – the right element of this pair. Value is null.
Returns:
an immutable pair of nulls.
Since:
3.6/**
     * Returns an immutable pair of nulls.
     *
     * @param <L> the left element of this pair. Value is {@code null}.
     * @param <R> the right element of this pair. Value is {@code null}.
     * @return an immutable pair of nulls.
     * @since 3.6
     */
    public static <L, R> ImmutablePair<L, R> nullPair() {
        return NULL;
    }

    
Creates an immutable pair of two objects inferring the generic types.
This factory allows the pair to be created using inference to
obtain the generic types.
Params:
left –  the left element, may be null
right –  the right element, may be null
Type parameters:
<L> – the left element type
<R> – the right element type
Returns:
a pair formed from the two parameters, not null/**
     * <p>Creates an immutable pair of two objects inferring the generic types.</p>
     *
     * <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> ImmutablePair<L, R> of(final L left, final R right) {
        return new ImmutablePair<>(left, right);
    }

    
Creates an immutable pair from an existing pair.
This factory allows the pair to be created using inference to
obtain the generic types.
Params:
pair – the existing pair.
Type parameters:
<L> – the left element type
<R> – the right element type
Returns:
a pair formed from the two parameters, not null
Since:
3.10/**
     * <p>Creates an immutable pair from an existing pair.</p>
     *
     * <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 pair the existing pair.
     * @return a pair formed from the two parameters, not null
     * @since 3.10
     */
    public static <L, R> ImmutablePair<L, R> of(final Map.Entry<L, R> pair) {
        final L left;
        final R right;
        if (pair != null) {
            left = pair.getKey();
            right = pair.getValue();
        } else {
            left = null;
            right = null;
        }
        return new ImmutablePair<>(left, right);
    }

    
Creates an immutable pair of two objects inferring the generic types.
This factory allows the pair to be created using inference to
obtain the generic types.
Params:
right –  the right element, may be null
Type parameters:
<L> – the left element type
<R> – the right element type
Returns:
a pair formed from the two parameters, not null
Since:
3.11/**
     * <p>Creates an immutable pair of two objects inferring the generic types.</p>
     *
     * <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 right  the right element, may be null
     * @return a pair formed from the two parameters, not null
     * @since 3.11
     */
    public static <L, R> Pair<L, R> right(final R right) {
        return ImmutablePair.of(null, right);
    }

    
Left object /** Left object */
    public final L left;

    
Right object /** Right object */
    public final R right;

    
Create a new pair instance.
Params:
left –  the left value, may be null
right –  the right value, may be null/**
     * Create a new pair instance.
     *
     * @param left  the left value, may be null
     * @param right  the right value, may be null
     */
    public ImmutablePair(final L left, final R right) {
        super();
        this.left = left;
        this.right = right;
    }

    
{@inheritDoc}
/**
     * {@inheritDoc}
     */
    @Override
    public L getLeft() {
        return left;
    }

    
{@inheritDoc}
/**
     * {@inheritDoc}
     */
    @Override
    public R getRight() {
        return right;
    }

    
Throws UnsupportedOperationException.
This pair is immutable, so this operation is not supported.
Params:
value –  the value to set
Throws:
UnsupportedOperationException – as this operation is not supported
Returns:
never/**
     * <p>Throws {@code UnsupportedOperationException}.</p>
     *
     * <p>This pair is immutable, so this operation is not supported.</p>
     *
     * @param value  the value to set
     * @return never
     * @throws UnsupportedOperationException as this operation is not supported
     */
    @Override
    public R setValue(final R value) {
        throw new UnsupportedOperationException();
    }

}