Java reference

Objects.requireNonNull()

Checks that a value is not null and throws NullPointerException with a clear message right away.

Available since: Java 7

Syntax

static <T> T requireNonNull(T obj, String message)

Parameters

Parameter	Type	Description
obj	T	The value to check.
message	String	The error text. Optional.

Return value

TThe same value if it is not null — so the call fits right into an assignment.

Examples

Checking an argument in a constructor:

class User {
    final String name;
 
    User(String name) {
        this.name = Objects.requireNonNull(name, "name must not be null");
    }
}
 
void main() {
    IO.println(new User("Anna").name);
    try {
        new User(null);
    } catch (NullPointerException e) {
        IO.println(e.getMessage());
    }
}

Output:

Anna
name must not be null

A default instead of null — requireNonNullElse() (Java 9):

void main() {
    String nickname = null;
    IO.println(Objects.requireNonNullElse(nickname, "guest"));
}

Output:

guest

Notes

The error appears right when the object is created rather than later, when the null blows up somewhere else — which makes the cause easier to find.

Related recipes

In the tutorial

Encapsulation — Encapsulation in Java: the private modifier, getters and setters, data validation and final fields.

Thanks for reading!