GridTuple.java

/*
 * 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.ignite.internal.util.lang;

import java.io.Externalizable;
import java.io.IOException;
import java.io.ObjectInput;
import java.io.ObjectOutput;
import java.util.Iterator;
import java.util.NoSuchElementException;
import org.apache.ignite.internal.util.tostring.GridToStringInclude;
import org.apache.ignite.internal.util.typedef.internal.S;
import org.jetbrains.annotations.Nullable;

/**
 * Convenience class representing mutable tuple of a single value.
 * <h2 class="header">Thread Safety</h2>
 * This class doesn't provide any synchronization for multi-threaded access
 * and it is responsibility of the user of this class to provide outside
 * synchronization, if needed.
 */
public class GridTuple<V> implements Iterable<V>, Cloneable, Externalizable {
    /** */
    private static final long serialVersionUID = 0L;

    /** The value to wrap. */
    @GridToStringInclude
    private V val;

    /**
     * Empty constructor required by {@link Externalizable}.
     */
    public GridTuple() {
        // No-op.
    }

    /**
     * Constructs mutable object with given value.
     *
     * @param val Wrapped value.
     */
    public GridTuple(@Nullable V val) {
        this.val = val;
    }

    /**
     * Gets value.
     *
     * @return Wrapped value.
     */
    @Nullable public V get() {
        return val;
    }

    /**
     * Sets value.
     *
     * @param val Value to set.
     */
    public void set(@Nullable V val) {
        this.val = val;
    }

    /** {@inheritDoc} */
    @Override public Iterator<V> iterator() {
        return new Iterator<V>() {
            private boolean hasNext = true;

            @Override public boolean hasNext() {
                return hasNext;
            }

            @Override public V next() {
                if (!hasNext())
                    throw new NoSuchElementException();

                hasNext = false;

                return val;
            }

            @Override public void remove() {
                throw new UnsupportedOperationException();
            }
        };
    }

    /** {@inheritDoc} */
    @SuppressWarnings({"CloneDoesntDeclareCloneNotSupportedException"})
    @Override public Object clone() {
        try {
            return super.clone();
        }
        catch (CloneNotSupportedException ignore) {
            throw new InternalError();
        }
    }

    /** {@inheritDoc} */
    @Override public void writeExternal(ObjectOutput out) throws IOException {
        out.writeObject(val);
    }

    /** {@inheritDoc} */
    @SuppressWarnings({"unchecked"})
    @Override public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException {
        val = (V)in.readObject();
    }

    /** {@inheritDoc} */
    @Override public int hashCode() {
        return val == null ? 0 : val.hashCode();
    }

    /** {@inheritDoc} */
    @Override public boolean equals(Object obj) {
        if (obj == this)
            return true;

        if (!(obj instanceof GridTuple))
            return false;

        GridTuple t = (GridTuple)obj;

        // Both nulls or equals.
        return val == null ? t.val == null : val.equals(t.val);
    }

    /** {@inheritDoc} */
    @Override public String toString() {
        return S.toString(GridTuple.class, this);
    }
}