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Silk Java dependency injection framework

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/*
 *  Copyright (c) 2012, Jan Bernitt 
 *			
 *  Licensed under the Apache License, Version 2.0, http://www.apache.org/licenses/LICENSE-2.0
 */
package se.jbee.inject;

/**
 * How frequently do instances expire (become garbage, are not used any longer).
 * 
 * @author Jan Bernitt ([email protected])
 */
public final class Expiry {

	public static final Expiry NEVER = new Expiry( 0 );

	public static Expiry expires( int frequency ) {
		if ( frequency < 0 ) {
			throw new IllegalArgumentException( Expiry.class.getSimpleName()
					+ " frequency cannot be negative but was: " + frequency );
		}
		return new Expiry( frequency );
	}

	private final int frequency;

	public Expiry( int frequency ) {
		super();
		this.frequency = frequency;
	}

	public boolean equalTo( Expiry other ) {
		return frequency == other.frequency;
	}

	public boolean moreFrequent( Expiry other ) {
		return frequency > other.frequency;
	}

	@Override
	public String toString() {
		return String.valueOf( frequency );
	}

	@Override
	public boolean equals( Object obj ) {
		return obj instanceof Expiry && ( (Expiry) obj ).frequency == frequency;
	}

	@Override
	public int hashCode() {
		return frequency;
	}

	public boolean isNever() {
		return frequency == 0;
	}

}