Here you can find the source of assertState(boolean expression)
public static void assertState(boolean expression)
//package com.java2s; // The MIT License (MIT) public class Main { public static void assertState(boolean expression) { if (!expression) { throw new IllegalStateException(); }/*from w w w . j a v a 2 s .c o m*/ } public static void assertState(boolean expression, String errorMessage) { if (!expression) { throw new IllegalStateException(errorMessage); } } }