code: public static void checkArgument(
              boolean expression, String messageFormat, Object... messageArgs) {
          if (!expression) {
              throw new IllegalArgumentException(format(messageFormat, messageArgs));
          }
      }
docs: Checks the truth of the given expression and throws a customized
  {@link IllegalArgumentException} if it is false. Intended for doing parameter validation in
  methods and constructors, e.g.:
  <blockquote><pre>
  public void foo(int count) {
  Preconditions.checkArgument(count > 0, "count must be positive: %s.", count);
  }
  </pre></blockquote>
  
  @param expression the precondition to check involving one ore more parameters to the calling
  method or constructor
  @param messageFormat a {@link Formatter format} string for the detail message to be used in
  the event that an exception is thrown.
  @param messageArgs the arguments referenced by the format specifiers in the
  {@code messageFormat}
  @throws IllegalArgumentException if {@code expression} is false