de.flapdoodle.guava.Either.java Source code

Introduction

Here is the source code for de.flapdoodle.guava.Either.java

Source

/**
 * Copyright (C) 2013
 *   Michael Mosmann <michael@mosmann.de>
 *
 * 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 de.flapdoodle.guava;

import java.io.Serializable;

import com.google.common.base.Preconditions;

public abstract class Either<L, R> implements Serializable {

    public abstract boolean isLeft();

    public abstract L left();

    public abstract R right();

    public static <L, R> Left<L, R> left(L value) {
        return new Left<L, R>(value);
    }

    public static <L, R> Right<L, R> right(R value) {
        return new Right<L, R>(value);
    }

    public static <L, R> Either<L, R> leftOrRight(L left, R right, String errorMessage) {
        Preconditions.checkArgument(Logics.xor(left, right), errorMessage);
        if (left != null) {
            return left(left);
        }
        return right(right);
    }

    public static <L, R> Either<L, R> leftOrRight(L left, R right) {
        return leftOrRight(left, right, "only left or right");
    }

    public static final class Left<L, R> extends Either<L, R> {

        private final L value;

        public Left(L value) {
            this.value = value;
        }

        @Override
        public boolean isLeft() {
            return true;
        }

        @Override
        public L left() {
            return value;
        }

        @Override
        public R right() {
            throw new NullPointerException("is left");
        }

        @Override
        public int hashCode() {
            final int prime = 31;
            int result = 1;
            result = prime * result + ((value == null) ? 0 : value.hashCode());
            return result;
        }

        @Override
        public boolean equals(Object obj) {
            if (this == obj)
                return true;
            if (obj == null)
                return false;
            if (getClass() != obj.getClass())
                return false;
            Left<?, ?> other = (Left<?, ?>) obj;
            if (value == null) {
                if (other.value != null)
                    return false;
            } else if (!value.equals(other.value))
                return false;
            return true;
        }

    }

    public static final class Right<L, R> extends Either<L, R> {

        private final R value;

        public Right(R value) {
            this.value = value;
        }

        @Override
        public boolean isLeft() {
            return false;
        }

        @Override
        public L left() {
            throw new NullPointerException("is right");
        }

        @Override
        public R right() {
            return value;
        }

        @Override
        public int hashCode() {
            final int prime = 31;
            int result = 1;
            result = prime * result + ((value == null) ? 0 : value.hashCode());
            return result;
        }

        @Override
        public boolean equals(Object obj) {
            if (this == obj)
                return true;
            if (obj == null)
                return false;
            if (getClass() != obj.getClass())
                return false;
            Right<?, ?> other = (Right<?, ?>) obj;
            if (value == null) {
                if (other.value != null)
                    return false;
            } else if (!value.equals(other.value))
                return false;
            return true;
        }

    }
}