State.java

/*
 * Copyright (c) OSGi Alliance (2002, 2009). All Rights Reserved.
 *
 * 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.osgi.util.measurement;

/**
 * Groups a state name, value and timestamp.
 * 
 * <p>
 * The state itself is represented as an integer and the time is measured in
 * milliseconds since midnight, January 1, 1970 UTC.
 * 
 * <p>
 * A <tt>State</tt> object is immutable so that it may be easily shared.
 * 
 * @version $Revision: 1.1 $
 * @author Open Services Gateway Initiative
 */

public class State {
	final int value;
	final long time;
	final String name;

	/**
	 * Create a new <tt>State</tt> object.
	 * 
	 * @param value
	 *            The value of the state.
	 * @param name
	 *            The name of the state.
	 * @param time
	 *            The time measured in milliseconds since midnight, January 1,
	 *            1970 UTC.
	 */
	public State(int value, String name, long time) {
		this.value = value;
		this.name = name;
		this.time = time;
	}

	/**
	 * Create a new <tt>State</tt> object with a time of 0.
	 * 
	 * @param value
	 *            The value of the state.
	 * @param name
	 *            The name of the state.
	 */
	public State(int value, String name) {
		this(value, name, 0);
	}

	/**
	 * Returns the value of this <tt>State</tt>.
	 * 
	 * @return The value of this <tt>State</tt> object.
	 */
	public final int getValue() {
		return value;
	}

	/**
	 * Returns the time with which this <tt>State</tt> was created.
	 * 
	 * @return The time with which this <tt>State</tt> was created. The time
	 *         is measured in milliseconds since midnight, January 1, 1970 UTC.
	 */
	public final long getTime() {
		return time;
	}

	/**
	 * Returns the name of this <tt>State</tt>.
	 * 
	 * @return The name of this <tt>State</tt> object.
	 */
	public final String getName() {
		return name;
	}

	/**
	 * Returns a <tt>String</tt> object representing this object.
	 * 
	 * @return a <tt>String</tt> object representing this object.
	 */
	public String toString() {
		StringBuffer sb = new StringBuffer();

		sb.append(value);

		if (name != null) {
			sb.append(" \"");
			sb.append(name);
			sb.append("\"");
		}

		return (sb.toString());
	}

	/**
	 * Returns a hash code value for this object.
	 * 
	 * @return A hash code value for this object.
	 */
	public int hashCode() {
		int hash = value;

		if (name != null) {
			hash ^= name.hashCode();
		}

		return hash;
	}

	/**
	 * Return whether the specified object is equal to this object. Two
	 * <tt>State</tt> objects are equal if they have same value and name.
	 * 
	 * @param obj
	 *            The object to compare with this object.
	 * @return <tt>true</tt> if this object is equal to the specified object;
	 *         <tt>false</tt> otherwise.
	 */
	public boolean equals(Object obj) {
		if (this == obj) {
			return true;
		}

		if (!(obj instanceof State)) {
			return false;
		}

		State that = (State) obj;

		if (value != that.value) {
			return false;
		}

		if (name == that.name) {
			return true;
		}

		if (name == null) {
			return false;
		}

		return name.equals(that.name);
	}
}