TennisBall.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.mina.example.tennis;

/**
 * A tennis ball which has TTL value and state whose value is one of 'PING' and
 * 'PONG'.
 *
 * @author <a href="http://mina.apache.org">Apache MINA Project</a>
 */
public class TennisBall {
    private final boolean ping;

    private final int ttl;

    /**
     * Creates a new ball with the specified TTL (Time To Live) value.
     */
    public TennisBall(int ttl) {
        this(ttl, true);
    }

    /**
     * Creates a new ball with the specified TTL value and PING/PONG state.
     */
    private TennisBall(int ttl, boolean ping) {
        this.ttl = ttl;
        this.ping = ping;
    }

    /**
     * Returns the TTL value of this ball.
     */
    public int getTTL() {
        return ttl;
    }

    /**
     * Returns the ball after {@link TennisPlayer}'s stroke.
     * The returned ball has decreased TTL value and switched PING/PONG state.
     */
    public TennisBall stroke() {
        return new TennisBall(ttl - 1, !ping);
    }

    /**
     * Returns string representation of this message (<code>[PING|PONG]
     * (TTL)</code>).
     */
    @Override
    public String toString() {
        if (ping) {
            return "PING (" + ttl + ")";
        } else {
            return "PONG (" + ttl + ")";
        }
    }
}