getClass method

The getClass() method can be used to find the runtime class type of an object. See the example below:

public class User {
   
    private long userID;
    private String name;

    public User(long userID, String name) {
        this.userID = userID;
        this.name = name;
    }
}

public class SpecificUser extends User {
    private String specificUserID;

    public SpecificUser(String specificUserID, long userID, String name) {
        super(userID, name);
        this.specificUserID = specificUserID;
    }
}

public static void main(String[] args){
    User user = new User(879745, "John");
    SpecificUser specificUser = new SpecificUser("1AAAA", 877777, "Jim");
    User anotherSpecificUser = new SpecificUser("1BBBB", 812345, "Jenny");

    System.out.println(user.getClass()); //Prints "class User"
    System.out.println(specificUser.getClass()); //Prints "class SpecificUser"
    System.out.println(anotherSpecificUser.getClass()); //Prints "class SpecificUser"
}

The getClass() method will return the most specific class type, which is why when getClass() is called on anotherSpecificUser, the return value is class SpecificUser because that is lower down the inheritance tree than User.

It is noteworthy that, while the getClass method is declared as:

public final native Class<?> getClass();

The actual static type returned by a call to getClass is Class<? extends T> where T is the static type of the object on which getClass is called.

i.e. the following will compile:

Class<? extends String> cls = "".getClass();

Found a mistake? Have a question or improvement idea? Let me know.

Table Of Contents