The _ () sign in Java is a kind of constructor

I am new to Java and started learning and learning a little about the language. Can anyone explain what is the meaning of _ () in this constructor. Is this a called constructor?

public class UserRequestCache {

    private final static ThreadLocal <UserRequest> t = new ThreadLocal <UserRequest>();

    private static UserRequestCache instance = new UserRequestCache();

    public static UserRequestCache _() {
        return instance;
    }

    private UserRequestCache() {
    }

    public void checkPoint() {
        if (logDebug()) {
            if (getUserRequest() != null) {
                logDebug(getUserRequest().toString());
            }
        }
    }

    public UserRequest getCache() {
        // checkPoint();
        return getUserRequest();
    }

    private UserRequest getUserRequest() {
        return t.get();
    }

    public void setCache(UserRequest value) {
        t.set(value);
    }
}