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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.hudi.common.util.collection;

import java.io.Serializable;
import java.util.Map;

/**
 * (NOTE: Adapted from Apache commons-lang3)
 * 

* A pair consisting of two elements. *

* *

* 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'. *

* *

* 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. *

* * @param the left element type * @param the right element type */ public abstract class Pair implements Map.Entry, Comparable>, Serializable { /** * Serialization version. */ private static final long serialVersionUID = 4954918890077093841L; /** *

* Obtains an immutable pair of from two objects inferring the generic types. *

* *

* This factory allows the pair to be created using inference to obtain the generic types. *

* * @param the left element type * @param 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 Pair of(final L left, final R right) { return new ImmutablePair<>(left, right); } // ----------------------------------------------------------------------- /** *

* Gets the left element from this pair. *

* *

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

* * @return the left element, may be null */ public abstract L getLeft(); /** *

* Gets the right element from this pair. *

* *

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

* * @return the right element, may be null */ public abstract R getRight(); /** *

* Gets the key from this pair. *

* *

* This method implements the {@code Map.Entry} interface returning the left element as the key. *

* * @return the left element as the key, may be null */ @Override public final L getKey() { return getLeft(); } /** *

* Gets the value from this pair. *

* *

* This method implements the {@code Map.Entry} interface returning the right element as the value. *

* * @return the right element as the value, may be null */ @Override public R getValue() { return getRight(); } // ----------------------------------------------------------------------- /** *

* Compares the pair based on the left element followed by the right element. The types must be {@code Comparable}. *

* * @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 other) { checkComparable(this); checkComparable(other); Comparable thisLeft = (Comparable) getLeft(); Comparable thisRight = (Comparable) getRight(); Comparable otherLeft = (Comparable) other.getLeft(); Comparable otherRight = (Comparable) other.getRight(); if (thisLeft.compareTo(otherLeft) == 0) { return thisRight.compareTo(otherRight); } else { return thisLeft.compareTo(otherLeft); } } /** *

* 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 */ @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 getKey().equals(other.getKey()) && getValue().equals(other.getValue()); } return false; } /** *

* Returns a suitable hash code. The hash code follows the definition in {@code Map.Entry}. *

* * @return the hash code */ @Override public int hashCode() { // see Map.Entry API specification return (getKey() == null ? 0 : getKey().hashCode()) ^ (getValue() == null ? 0 : getValue().hashCode()); } /** *

* 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(); } /** *

* Formats the receiver using the given format. *

* *

* 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)}. *

* * @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()); } private void checkComparable(Pair pair) { if (!(pair.getLeft() instanceof Comparable) || !(pair.getRight() instanceof Comparable)) { throw new IllegalArgumentException("Elements of Pair must implement Comparable :" + pair); } } }




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