package listener;

import gov.nasa.jpf.ListenerAdapter;
import gov.nasa.jpf.vm.VM;
import gov.nasa.jpf.vm.VMListener;

/**
 * This listener prints the amount of time (in milliseconds) taken by the garbage
 * collector each time the garbage collector is invoked.
 * 
 * @author Franck van Breugel
 */
public class Garbage extends ListenerAdapter implements VMListener {
	private long start; // when the garbage collector was last started
	
	/**
	 * Whenever the garbage collector starts, records the current time.
	 * 
	 * @param vm JPF's VM
	 */
	@Override
	public void gcBegin(VM vm) {
		this.start = System.currentTimeMillis();
	}
	
	/**
	 * Whenever the garbage collector ends, prints the amount of time it has taken.
	 * 
	 * @param vm JPF's VM
	 */
	public void gcEnd(VM vm) {
		System.out.println(System.currentTimeMillis() - this.start);
	}
}