org.spf4j.base.Either Maven / Gradle / Ivy

Go to download
/*
 * Copyright (c) 2001-2017, Zoltan Farkas All Rights Reserved.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 * Additionally licensed with:
 *
 * 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 org.spf4j.base;

import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
import java.util.concurrent.ExecutionException;
import javax.annotation.Nullable;

/**
 * @author zoly
 */
public abstract class Either {

    //CHECKSTYLE:OFF
    protected final Object value;
    //CHECKSTYLE:ON

    private Either(@Nullable final Object value) {
        this.value = value;
    }

    public abstract boolean isLeft();


    public boolean isRight() {
        return !isLeft();
    }


    public abstract  A getLeft();

    public abstract  B getRight();

    @Override
    public int hashCode() {
        return 73 + (this.value != null ? this.value.hashCode() : 0);
    }

    @Override
    public boolean equals(final Object obj) {
        if (obj == null) {
            return false;
        }
        if (getClass() != obj.getClass()) {
            return false;
        }
        final Either other = (Either) obj;
        return (!(this.value != other.value && (this.value == null || !this.value.equals(other.value))));
    }



    @Override
    public String toString() {
        return "Either(" + value + ')';
    }


    public static final class Left extends Either {

        public Left(final A a) {
            super(a);
        }

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

        @Override
        public A getLeft() {
            return (A) this.value;
        }

        @Override
        public B getRight() {
            throw new UnsupportedOperationException("This union doe not have a right val, instead a " + value);
        }

    }

    public static final class Right extends Either {

        public Right(final B b) {
           super(b);
        }

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

        @Override
        public A getLeft() {
            throw new UnsupportedOperationException("This union doe not have a left val, instead a " + value);
        }

        @Override
        public B getRight() {
            return (B) value;
        }
    }

    public static  Either left(final A a) {
        return new Left(a);
    }

    public static  Either right(final B b) {
        return new Right(b);
    }

    @SuppressFBWarnings("ITC_INHERITANCE_TYPE_CHECKING")
    public static  T processResult(final Either result)
            throws ExecutionException {
        if (result.isLeft()) {
            return result.getLeft();
        } else {
            Exception e = result.getRight();
            if (e instanceof RuntimeException) {
              throw (RuntimeException) e;
            } else if (e instanceof ExecutionException) {
              throw (ExecutionException) e;
            } else {
              throw new ExecutionException(e);
            }
        }
    }

}