About Question enthuware.ocajp.i.v7.2.1027 :

[ETS User]

Isn't Integer mutable if the value lies between -128 and 127. And so the increment here will acutally affect the Integer variable?

[admin]

No, none of the wrapper classes is mutable.
I think you are confusing interning with mutability. Integer objects for integers between -128 to 127 are interened. I.e. if you have the following two lines:
Integer i1 = 100;
Integer i2 = 100;
then i1 and i2 would be referring to the same Integer object.

HTH,
Paul.

[Guest]

Thanks Paul!

[bidya74]

public class TestClass{
public static Integer wiggler(Integer x){
Integer y = x + 10;
x++;
System.out.println(x);
return y;
}

public static void main(String[] args){
Integer dataWrapper = new Integer(5);
Integer value = wiggler(dataWrapper);
System.out.println(dataWrapper+value);
}
}

here the o/p: 6,20 so q is how 6 is coming since wrappers are immutable.

[radupana]

I don't believe the code will compile (at least the version I have, where Integer.valueof(5,16) is called).

There is no valueOf method that takes two ints, defined on Integer, in Java 21.
The closest is public static Integer valueOf(String s, int radix): https://docs.oracle.com/en/java/javase/ ... tring,int)

Even the explanation uses the (String, int) signature:
3. Note that the exam expects you to know the basics of hexadecimal numbers. Specifically, you should know that the hexadecimal system has 16 digits - 0 to 9 and a, b, c, d, e , f. Thus, Integer.valueof("a", 16), will return 10. The digit 5 in hexadecimal is the same as 5 in decimal though.

[admin]

Yes, it should be valueOf("5", 16). This was mistakenly updated from 5 to to 5, 16 in the most recent version. Integer.valueOf(5) is fine but Integer.valueOf(5, 16) is not.
Fixed.
thank you for your feedback!