Here you can find the source of isEmpty(Collection> c)
public static boolean isEmpty(Collection<?> c)
//package com.java2s; import java.util.Collection; import java.util.Map; public class Main { public static boolean isEmpty(Map<?, ?> c) { return c == null || c.isEmpty(); }//ww w .java 2 s. com public static boolean isEmpty(Collection<?> c) { return c == null || c.isEmpty(); } }