public class TestClass
{
	public class CheckFailure extends RuntimeException {
		public String msg;
		CheckFailure(String msg){ this.msg = msg; }
	}
	
	protected void check(boolean expr) throws CheckFailure{
		if (!expr) throw new CheckFailure("");
	}
	protected void check(String msg, boolean expr) throws CheckFailure{
		if (!expr) throw new CheckFailure(msg);
	}
}