Triple.java
/*
* 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
*
* https://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;
import java.io.Serializable;
import java.util.Objects;
import org.apache.commons.lang3.builder.CompareToBuilder;
/**
* A triple consisting of three elements.
*
* <p>This class is an abstract implementation defining the basic API.
* It refers to the elements as 'left', 'middle' and '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 triple, then the triple itself effectively becomes mutable.</p>
*
* @param <L> the left element type.
* @param <M> the middle element type.
* @param <R> the right element type.
* @since 3.2
*/
public abstract class Triple<L, M, R> implements Comparable<Triple<L, M, R>>, Serializable {
/** Serialization version */
private static final long serialVersionUID = 1L;
/**
* An empty array.
* <p>
* Consider using {@link #emptyArray()} to avoid generics warnings.
* </p>
*
* @since 3.10
*/
public static final Triple<?, ?, ?>[] EMPTY_ARRAY = {};
/**
* Returns the empty array singleton that can be assigned without compiler warning.
*
* @param <L> the left element type.
* @param <M> the middle 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, M, R> Triple<L, M, R>[] emptyArray() {
return (Triple<L, M, R>[]) EMPTY_ARRAY;
}
/**
* Obtains an immutable triple of three objects inferring the generic types.
*
* <p>This factory allows the triple to be created using inference to
* obtain the generic types.</p>
*
* @param <L> the left element type.
* @param <M> the middle element type.
* @param <R> 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 <L, M, R> Triple<L, M, R> of(final L left, final M middle, final R right) {
return ImmutableTriple.of(left, middle, right);
}
/**
* Obtains an immutable triple of three non-null objects inferring the generic types.
*
* <p>This factory allows the triple to be created using inference to
* obtain the generic types.</p>
*
* @param <L> the left element type.
* @param <M> the middle element type.
* @param <R> the right element type.
* @param left the left element, may not be null.
* @param middle the middle element, may not be null.
* @param right the right element, may not be null.
* @return a triple formed from the three parameters, not null.
* @throws NullPointerException if any input is null.
* @since 3.13.0
*/
public static <L, M, R> Triple<L, M, R> ofNonNull(final L left, final M middle, final R right) {
return ImmutableTriple.ofNonNull(left, middle, right);
}
/**
* Constructs a new instance.
*/
public Triple() {
// empty
}
/**
* Compares the triple based on the left element, followed by the middle element,
* finally the right element.
* The types must be {@link Comparable}.
*
* @param other the other triple, not null.
* @return negative if this is less, zero if equal, positive if greater.
*/
@Override
public int compareTo(final Triple<L, M, R> other) {
return new CompareToBuilder().append(getLeft(), other.getLeft())
.append(getMiddle(), other.getMiddle())
.append(getRight(), other.getRight()).toComparison();
}
/**
* Compares this triple to another based on the three elements.
*
* @param obj the object to compare to, null returns false.
* @return true if the elements of the triple are equal.
*/
@Override
public boolean equals(final Object obj) {
if (obj == this) {
return true;
}
if (obj instanceof Triple<?, ?, ?>) {
final Triple<?, ?, ?> other = (Triple<?, ?, ?>) obj;
return Objects.equals(getLeft(), other.getLeft())
&& Objects.equals(getMiddle(), other.getMiddle())
&& Objects.equals(getRight(), other.getRight());
}
return false;
}
/**
* Gets the left element from this triple.
*
* @return the left element, may be null.
*/
public abstract L getLeft();
/**
* Gets the middle element from this triple.
*
* @return the middle element, may be null.
*/
public abstract M getMiddle();
/**
* Gets the right element from this triple.
*
* @return the right element, may be null.
*/
public abstract R getRight();
/**
* Returns a suitable hash code.
* <p>
* The hash code is adapted from the definition in {@code Map.Entry}.
* </p>
*
* @return the hash code.
*/
@Override
public int hashCode() {
// See Map.Entry API specification
return Objects.hashCode(getLeft()) ^ Objects.hashCode(getMiddle()) ^ Objects.hashCode(getRight());
}
/**
* Returns a String representation of this triple using the format {@code (left,middle,right)}.
*
* @return a string describing this object, not null.
*/
@Override
public String toString() {
return "(" + getLeft() + "," + getMiddle() + "," + getRight() + ")";
}
/**
* Formats the receiver using the given format.
*
* <p>This uses {@link java.util.Formattable} to perform the formatting. Three variables may
* be used to embed the left and right elements. Use {@code %1$s} for the left
* element, {@code %2$s} for the middle and {@code %3$s} for the right element.
* The default format used by {@code toString()} is {@code (%1$s,%2$s,%3$s)}.</p>
*
* @param format the format string, optionally containing {@code %1$s}, {@code %2$s} and {@code %3$s}, not null.
* @return the formatted string, not null.
*/
public String toString(final String format) {
return String.format(format, getLeft(), getMiddle(), getRight());
}
}