how to convert unix timestamp to date time in java

/**
 * @author lautturi.com
 * Java example: how to convert timestamp to date in java
 */

import java.util.*;

public class Lautturi {
	
	public static void main(String[] args) {

		Date date = new Date();
		
		long epoch = 1515311799851L;
		date.setTime(epoch);
		
		System.out.println(epoch);
		System.out.println(date);
	}
}

output:

1515311799851
Sun Jan 07 15:56:39 CST 2018