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Apache Commons Lang, a package of Java utility classes for the classes that are in java.lang's hierarchy, or are considered to be so standard as to justify existence in java.lang. The code is tested using the latest revision of the JDK for supported LTS releases: 8, 11, 17 and 21 currently. See https://github.com/apache/commons-lang/blob/master/.github/workflows/maven.yml Please ensure your build environment is up-to-date and kindly report any build issues.

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

/**
 * An immutable triple consisting of three {@code 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 triple, then the triple
 * itself effectively becomes mutable. The class is also {@code final}, so a subclass
 * can not add undesirable behavior.
 *
 * #ThreadSafe# if all three objects are thread-safe
 *
 * @param  the left element type
 * @param  the middle element type
 * @param  the right element type
 *
 * @since 3.2
 */
public final class ImmutableTriple extends Triple {

    /**
     * An empty array.
     * 
     * Consider using {@link #emptyArray()} to avoid generics warnings.
     * 
     *
     * @since 3.10.
     */
    public static final ImmutableTriple[] EMPTY_ARRAY = new ImmutableTriple[0];

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

    /** Serialization version */
    private static final long serialVersionUID = 1L;

    /**
     * Returns the empty array singleton that can be assigned without compiler warning.
     *
     * @param  the left element type
     * @param  the middle element type
     * @param  the right element type
     * @return the empty array singleton that can be assigned without compiler warning.
     *
     * @since 3.10.
     */
    @SuppressWarnings("unchecked")
    public static  ImmutableTriple[] emptyArray() {
        return (ImmutableTriple[]) EMPTY_ARRAY;
    }

    /**
     * Returns an immutable triple of nulls.
     *
     * @param  the left element of this triple. Value is {@code null}.
     * @param  the middle element of this triple. Value is {@code null}.
     * @param  the right element of this triple. Value is {@code null}.
     * @return an immutable triple of nulls.
     * @since 3.6
     */
    public static  ImmutableTriple nullTriple() {
        return NULL;
    }

    /**
     * Obtains an immutable triple of three objects inferring the generic types.
     *
     * This factory allows the triple to be created using inference to
     * obtain the generic types.
     *
     * @param  the left element type
     * @param  the middle element type
     * @param  the right element type
     * @param left  the left element, may be null
     * @param middle  the middle element, may be null
     * @param right  the right element, may be null
     * @return a triple formed from the three parameters, not null
     */
    public static  ImmutableTriple of(final L left, final M middle, final R right) {
        return new ImmutableTriple<>(left, middle, right);
    }
    /** Left object */
    public final L left;
    /** Middle object */
    public final M middle;

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

    /**
     * Create a new triple instance.
     *
     * @param left  the left value, may be null
     * @param middle the middle value, may be null
     * @param right  the right value, may be null
     */
    public ImmutableTriple(final L left, final M middle, final R right) {
        super();
        this.left = left;
        this.middle = middle;
        this.right = right;
    }

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

    /**
     * {@inheritDoc}
     */
    @Override
    public M getMiddle() {
        return middle;
    }

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