Why can't Java switch over the primitive long?

Question

Possible Duplicate:
Why can’t your switch statement data type be long, Java?

Why is something like that not possible?

private void importantFunction( long arg1 ) {

    switch (arg1){
    case 0:
         // do stuff
        break;
    case 1:
         // do other stuff
        break;
    default:
        //do default stuff
        break;
    }
}

The way I understand long values, there shouldn't be that much of a difference between them and integers.

http://stackoverflow.com/questions/2676210/why-cant-your-switch-statement-data-type-be-long-java — bartlaarhoven, Dec 19 '12 at 11:30
"Why is something like that not possible?" Its one of the things I like about the Java language, its designed to prevent you from introducing design flaws as far as is possible. If you are switching over a long value, you are doing something wrong. — Gimby, Dec 19 '12 at 13:34
Well it may be a bad decision if I would switching between a ton of values. But in my case I'm working with a proprietary api, which gives me a long value. I'm just checking if the value is 0, 1 or not set yet and a simple cast solves this in an easy way, but I was curious why Java does not allow it. A bad design with integer values is possible without any difficulties. The class Integer supports 2*2^31-1 different values. — Robert Schröder, Dec 19 '12 at 14:34

score 5 · Answer 1 · answered Dec 19 '12 at 11:36

5

As per Java 7 you could use a String: LINK TO ORACLE

So basicly this would allow String.valueOf(23423423L);

answered Dec 19 '12 at 11:36

IDKFA

436
3
5

score 5 · Answer 2 · answered Dec 19 '12 at 11:58

There are many, many features Java could have had. Language design is a continuous series of trade-offs between utility and complexity. Put in too many features, and the language becomes hard to learn and implement.

Obviously, one can have a long that has only a few possible values, so that it is reasonable to use it as a switch expression, but that is unusual. Mainly, long is used when there are too many values for int, and so far too many values for a switch expression.

One solution is a Map that maps the values of the long you would like to use to a small set of Integer values:

import java.util.HashMap;
import java.util.Map;

public class Test {
  public static void main(String[] args) {
    final int ONE_CASE = 3;
    final int ANOTHER_CASE = 4;
    Map<Long, Integer> map = new HashMap<Long, Integer>();
    map.put((long) 1e10, ONE_CASE);
    map.put((long) 1e11, ANOTHER_CASE);
    long arg1 = (long) 1e11;
    switch (map.get(arg1)) {
    case 3:
      System.out.println("ONE_CASE");
      break;
    case 4:
      System.out.println("ANOTHER_CASE");
      break;
    }
  }
}

+1 for the uniqueness of the answer.. – Amit Aug 22 '13 at 05:28 — Amit, Aug 22 '13 at 05:28

score 3 · Answer 3 · edited Jun 20 '20 at 09:12

3

JVM spec says: The Java virtual machine's tableswitch and lookupswitch instructions operate only on int data.

edited Jun 20 '20 at 09:12

Community

1
1

answered Dec 19 '12 at 11:35

Alexei Kaigorodov

13,189
1
21
38

score 0 · Answer 4 · answered Dec 19 '12 at 11:36

0

because Java doesn't want you to switch over those many options as a long can contain, so they restricted it to ints

answered Dec 19 '12 at 11:36

vishal_aim

7,636
1
20
23

2

that would be an awkward solution since integer can contain values up to 2^31-1 – Robert Schröder Dec 19 '12 at 12:44

Why can't Java switch over the primitive long?

4 Answers4