Here you can find the source of assertNotNull(final Object obj, final String reference)
public static void assertNotNull(final Object obj, final String reference)
//package com.java2s; //License from project: Apache License public class Main { public static void assertNotNull(final Object obj, final String reference) { if (obj == null) { throw new IllegalArgumentException(String .format("[Assertion failed error. Expected not null reference %s, but got <NULL>]", reference)); }//from w w w .java 2 s . c o m } }