com.github.hilcode.versionator.misc.Either.java Source code

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Here is the source code for com.github.hilcode.versionator.misc.Either.java

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/*
 * Copyright (C) 2016 H.C. Wijbenga
 *
 * 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.github.hilcode.versionator.misc;

import com.google.common.base.Preconditions;

public final class Either<L, R> {
    public static final <L, R> Either<L, R> left(final L value) {
        return new Either<>(value, null);
    }

    public static final <T, L, R> Either<L, R> asLeft(final Either<L, T> either) {
        Preconditions.checkArgument(either.isLeft(), "Invalid cast, this Either represents a Right.");
        @SuppressWarnings("unchecked")
        final Either<L, R> either_ = (Either<L, R>) either;
        return either_;
    }

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

    public static final <T, L, R> Either<L, R> asRight(final Either<T, R> either) {
        Preconditions.checkArgument(either.isRight(), "Invalid cast, this Either represents a Left.");
        @SuppressWarnings("unchecked")
        final Either<L, R> either_ = (Either<L, R>) either;
        return either_;
    }

    private final L left;

    private final R right;

    private Either(final L left, final R right) {
        Preconditions.checkArgument(left != null && right == null || left == null && right != null,
                "Invalid left/right.");
        this.left = left;
        this.right = right;
    }

    public final boolean isLeft() {
        return this.left != null;
    }

    public final boolean isRight() {
        return this.right != null;
    }

    public final L left() {
        Preconditions.checkNotNull(this.left, "This Either represents a Right.");
        return this.left;
    }

    public final R right() {
        Preconditions.checkNotNull(this.right, "This Result represents a Left.");
        return this.right;
    }

    @Override
    public String toString() {
        final StringBuilder builder = new StringBuilder();
        builder.append("(Either");
        if (isLeft()) {
            builder.append(" left=<").append(this.left).append('>');
        } else {
            builder.append(" right=<").append(this.right).append('>');
        }
        builder.append(")");
        return builder.toString();
    }
}