Method checkType

src/main/java/groovy/lang/Sequence.java:289–302

Checks that the given object instance is of the correct type otherwise a runtime exception is thrown

(Object object)

     * otherwise a runtime exception is thrown
     */
    protected void checkType(Object object) {
        if (object == null) {
            throw new NullPointerException("Sequences cannot contain null, use a List instead");
        }
        if (type != null) {
            if (!type.isInstance(object)) {
                throw new IllegalArgumentException(
                        "Invalid type of argument for sequence of type: "
                                + type.getName()
                                + " cannot add object: "
                                + object);
            }
        }
    }
}