guava/src/com/google/common/base/Verify.java
public static void verify(
      boolean expression,
      @Nullable String errorMessageTemplate,
      @Nullable Object @Nullable ... errorMessageArgs) {
    if (!expression) {
      throw new VerifyException(lenientFormat(errorMessageTemplate, errorMessageArgs));
    }
  }
public static void verify(
      boolean expression,
      @Nullable String errorMessageTemplate,
      @Nullable Object @Nullable ... errorMessageArgs) {
    if (!expression) {
      throw new VerifyException(lenientFormat(errorMessageTemplate, errorMessageArgs));
    }
  }
Ensures that {@code expression} is {@code true}, throwing a {@code VerifyException} with a
custom message otherwise.

@param expression a boolean expression
@param errorMessageTemplate a template for the exception message should the check fail. The
message is formed by replacing each {@code %s} placeholder in the template with an
argument. These are matched by position - the first {@code %s} gets {@code
errorMessageArgs[0]}, etc. Unmatched arguments will be appended to the formatted message in
square braces. Unmatched placeholders will be left as-is.
@param errorMessageArgs the arguments to be substituted into the message template. Arguments
are converted to strings using {@link String#valueOf(Object)}.
@throws VerifyException if {@code expression} is {@code false}
@see Preconditions#checkState Preconditions.checkState()