Thread: assert() function is not working. Why?

The following program is not working as I want. The assert() function is not working while I'm entering a number which is out of range 0-10. Whereas, according to my book, it is working like that:

Output:
Enter a number between 0 and 10: 50
Exception in thread "main" java.lang.AssertionError: bad number: 50
at AssertionTest.main(AssertTest.java:15)


But I cannot see the error message above after compiling the program on eclipse and netbeans. I just see that:

Output:
Enter a number between 0 and 10: 50
You entered 50

What is the problem? Why the function assert is not working?

import java.util.Scanner;
 
public class Assertion {
 
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
 
        System.out.print("Enter a number between 0 and 10: ");
        int number = input.nextInt();
 
        assert(number >= 0 && number <= 10) : "bad number: " + number; // assert, "bildir" demektir.
 
        System.out.printf("You entered %d\n",number);
    }
 
}

assert is not a function, its a keyword. Its a build in feature that must be enabled before it can be used.

To enable this feature you have to add the command "-ea" to the argument list when initializing your JVM.
Your IDE should give you the option to set a Run-Configuration where you can select the JVM commands to be used when testing your application. Make sure to add the command to the correct list.

Thank you so much Cornix. I did it in Eclipse and Netbeans like that:

In Eclipse:
Run->Run Configurations->Arguments->VM Arguments-> ....
I wrote -ea in VM Arguments.

In Netbeans:
Run->Set Project Configuration->Customize->VM Options->...
I wrote -ea in VM Options.