public static boolean assert(boolean result) 
{
	return assert(result, null);
}

 public static boolean assert(boolean result,
    String error) 
{
	if (!result) {
	    System.err.print("Assertion failed: ");
	    if (error != null) {
		System.err.print(error);
	    }
	    System.err.println();
	    System.err.println(getSourceLocation());
	}
	return result;
}

 public static boolean equals(String s1,
    String s2) 
{
        boolean result = ((s1 != null && s1.equals(s2))
			  || (s1 == null && s2 == null));
	if (!result) {
	    assert(result);
	    System.err.println("  was: equals(" + s1 + ", \"" + s2 + "\")");
	}
	return result;
}

 public static String getSourceLocation() 
{
	RuntimeException ex = new RuntimeException("assertion failed");
	StringWriter writer = new StringWriter();
	PrintWriter printer = new PrintWriter(writer);
	ex.printStackTrace(printer);
	String buf = writer.toString();
	// skip the first line as well as every line related to this class
	int index = buf.lastIndexOf("dom.util.Assertion.");
	index = buf.indexOf('\n", index);
	return buf.substring(index + 1);
}