public static void isTrue(boolean expression, String message) {
        if (!expression) {
            throw new IllegalArgumentException(message);
        }
    }
Assert a boolean expression, throwing {@code IllegalArgumentException}
if the test result is {@code false}.
<pre class="code">Assert.isTrue(i &gt; 0, "The value must be greater than zero");</pre>

@param expression a boolean expression
@param message    the exception message to use if the assertion fails
@throws IllegalArgumentException if expression is {@code false}
src/main/java/spark/utils/Assert.java