Java throw Keyword

Example

Throw an exception if age is below 18 (print "Access denied"). If age is 18 or older, print "Access granted":

public class Main {
  static void checkAge(int age) {
    if (age < 18) {
      throw new ArithmeticException("Access denied - You must be at least 18 years old.");
    }
    else {
      System.out.println("Access granted - You are old enough!");
    }
  }

  public static void main(String[] args) {
    checkAge(15); // Set age to 15 (which is below 18...)
  }
}

Try it Yourself »

Definition and Usage

The throw keyword is used to create a custom error.

The throw statement is used together with an exception type. There are many exception types available in Java: ArithmeticException, ClassNotFoundException, ArrayIndexOutOfBoundsException, SecurityException, etc.

The exception type is often used together with a custom method, like in the example above.

Differences between throw and throws:

throw	throws
Used to throw an exception for a method	Used to indicate what exception type may be thrown by a method
Cannot throw multiple exceptions	Can declare multiple exceptions
Syntax: `throw` is followed by an object (new type) used inside the method	Syntax: `throws` is followed by a class and used with the method signature