instanceof

An operator that tests whether an object is compatible with a given type.

What does instanceof do in Java?

instanceof — An operator that tests whether an object is compatible with a given type.

class LabelReader {
    int lengthOf(Object value) {
        if (value instanceof String text) {
            return text.length();
        }

        return 0;
    }
}

Level: Journeyman · More Java terms at this level

Updated September 27, 2026