| /* |
| * Copyright 2008 Google Inc. |
| * |
| * Licensed 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 com.google.gwt.dev.util; |
| |
| /** |
| * Functional-language like either type. Holds either left or right value. |
| * Values must be non-null. |
| * |
| * @param <L> left type. |
| * @param <R> right type. |
| */ |
| public class Either<L, R> { |
| public static <L, R> Either<L, R> left(L l) { |
| if (l == null) { |
| throw new IllegalArgumentException(); |
| } |
| return new Either<L, R>(l, null); |
| } |
| |
| public static <L, R> Either<L, R> right(R r) { |
| if (r == null) { |
| throw new IllegalArgumentException(); |
| } |
| return new Either<L, R>(null, r); |
| } |
| |
| private final L left; |
| |
| private final R right; |
| |
| private Either(L a, R b) { |
| left = a; |
| right = b; |
| } |
| |
| @SuppressWarnings("rawtypes") |
| @Override |
| public boolean equals(Object obj) { |
| if (this == obj) { |
| return true; |
| } |
| if (obj == null) { |
| return false; |
| } |
| if (getClass() != obj.getClass()) { |
| return false; |
| } |
| Either other = (Either) obj; |
| if (left != null && other.left != null) { |
| return left.equals(other.left); |
| } else if (right != null && other.right != null) { |
| return right.equals(other.right); |
| } |
| return false; |
| } |
| |
| public L getLeft() { |
| Preconditions.checkNotNull(left); |
| return left; |
| } |
| |
| public R getRight() { |
| Preconditions.checkNotNull(right); |
| return right; |
| } |
| |
| @Override |
| public int hashCode() { |
| final int prime = 31; |
| int result = 1; |
| result = prime * result + ((left == null) ? 0 : left.hashCode()); |
| result = prime * result + ((right == null) ? 0 : right.hashCode()); |
| return result; |
| } |
| |
| public boolean isLeft() { |
| return left != null; |
| } |
| |
| public boolean isRight() { |
| return right != null; |
| } |
| |
| @Override |
| public String toString() { |
| if (isLeft()) { |
| return "L{" + left.toString() + "}"; |
| } |
| return "R{" + right.toString() + "}"; |
| } |
| } |