diff options
Diffstat (limited to 'src/org/apache/commons/lang3/tuple/Pair.java')
| -rw-r--r-- | src/org/apache/commons/lang3/tuple/Pair.java | 176 |
1 files changed, 176 insertions, 0 deletions
diff --git a/src/org/apache/commons/lang3/tuple/Pair.java b/src/org/apache/commons/lang3/tuple/Pair.java new file mode 100644 index 0000000..cd24e79 --- /dev/null +++ b/src/org/apache/commons/lang3/tuple/Pair.java @@ -0,0 +1,176 @@ +/*
+ * 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;
+
+import java.io.Serializable;
+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>
+ *
+ * <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
+ * @version $Id: Pair.java 1142401 2011-07-03 08:30:12Z bayard $
+ */
+public abstract class Pair<L, R> implements Map.Entry<L, R>, Comparable<Pair<L, R>>, Serializable {
+
+ /** Serialization version */
+ private static final long serialVersionUID = 4954918890077093841L;
+
+ /**
+ * <p>Obtains an immutable pair of from 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> Pair<L, R> of(L left, R right) {
+ return new ImmutablePair<L, R>(left, right);
+ }
+
+ //-----------------------------------------------------------------------
+ /**
+ * <p>Gets the left element from this pair.</p>
+ *
+ * <p>When treated as a key-value pair, this is the key.</p>
+ *
+ * @return the left element, may be null
+ */
+ public abstract L getLeft();
+
+ /**
+ * <p>Gets the right element from this pair.</p>
+ *
+ * <p>When treated as a key-value pair, this is the value.</p>
+ *
+ * @return the right element, may be null
+ */
+ public abstract R getRight();
+
+ /**
+ * <p>Gets the key from this pair.</p>
+ *
+ * <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
+ */
+ public final L getKey() {
+ return getLeft();
+ }
+
+ /**
+ * <p>Gets the value from this pair.</p>
+ *
+ * <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
+ */
+ 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
+ */
+ public int compareTo(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.</p>
+ *
+ * @param obj the object to compare to, null returns false
+ * @return true if the elements of the pair are equal
+ */
+ @Override
+ public boolean equals(Object obj) {
+ if (obj == this) {
+ return true;
+ }
+ if (obj instanceof Map.Entry<?, ?>) {
+ 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)}.</p>
+ *
+ * @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>
+ *
+ * <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(String format) {
+ return String.format(format, getLeft(), getRight());
+ }
+
+}
|