How are "ranges" defined in Java?

Question

I have a chunk of code that needs to determine if a given integer is between a set of other integers. I'd also like to have this in a case statement so as to not have a surplus of if..else statements everywhere. Here's a bit of the code:

switch (copies) {
        case copies >= 0 && copies <= 99: copyPrice = 0.30; break;
        case copies >= 100 && copies <= 499: copyPrice = 0.28; break;
        case copies >= 500 && copies <= 749: copyPrice = 0.27; break;
        case copies >= 750 && copies <= 1000: copyPrice = 0.26; break;
        case copies > 1000: copies = 0.25; break;
    }

where copies is an integer and copyPrice is a double. I get several errors saying that it expects to receive a integer but gets a boolean instead. What is the best (or optimal) way of setting this up? Any help is greatly appreciated!

What's the point of the case vs if-else? You have just as many cases as you would if else statements. — turbo, Feb 11 '14 at 15:11
"expects to receive a boolean but gets a double." - I think the error was saying the opposite. — Maroun, Feb 11 '14 at 15:12
Check out this post http://stackoverflow.com/questions/7721332/ranges-in-java-whats-the-best-approach — mikemil, Feb 11 '14 at 15:12
Can you please post the exact error and the line referenced in the error? — m0skit0, Feb 11 '14 at 15:14
Here @m0skit0: found : boolean required: int case copies >= 100 && copies <= 499: copyPrice = 0.28; break; — T145, Feb 11 '14 at 15:24
I t hink this is the best explanation for your case on Stack Overflow: http://stackoverflow.com/questions/10873590/in-java-using-switch-statement-with-a-range-of-value-in-each-case — msmolcic, Feb 11 '14 at 15:29
@msmolcic92 every `if-else` solution is ugly for this use case. It would be better to use a `NavigableMap` — Luiggi Mendoza, Feb 11 '14 at 15:33
@Luiggi Mendoza yes, you're right. You solved the problem nicely, I love it. +1 — msmolcic, Feb 11 '14 at 15:36

Luiggi Mendoza · Accepted Answer · 2014-02-11T15:32:30.493

This line (and similar):

case copies >= 0 && copies <= 99:

Returns a compiler error since it gives a boolean but the compiler expects an int since copy is declared as int.

One way to solve this is using an array with the desired ranks, and have a switch statement for the index found:

public double calculateCopyPrice(int copies) {
    int[] range = { 99, 499, 749, 1000 };
    double copyPrice = 0;
    int index = -1;
    for (int i = 0; i < range.length; i++) {
        if (range[i] >= copies) {
            index = i;
            break;
        }
    }
    switch (index) {
        case 0: copyPrice = 0.30; break;
        case 1: copyPrice = 0.28; break;
        case 2: copyPrice = 0.27; break;
        case 3: copyPrice = 0.26; break;
        default: copyPrice = 0.25; break; 
    }
    //probably more logic here...
    return copyPrice;
}

After some tests, I've found a more flexible solution using a TreeMap<Integer, Double> which allows you to have a specie of range (what you're looking for) and ease the search by using TreeMap#ceilingEntry:

//TreeMap to store the "ranges"
TreeMap<Integer, Double> theMap = new TreeMap<Integer, Double>();
//add the data
theMap.put(99, 0.3);
theMap.put(499, 0.28);
theMap.put(749, 0.27);
theMap.put(1000, 0.26);
//the "default" value for max entries
theMap.put(Integer.MAX_VALUE, 0.25);
//testing the solution
Double ex1 = theMap.ceilingEntry(50).getValue();
Double ex2 = theMap.ceilingEntry(500).getValue();
Double ex3 = theMap.ceilingEntry(5000).getValue();
Double ex4 = theMap.ceilingEntry(100).getValue();
System.out.println(ex1);
System.out.println(ex2);
System.out.println(ex3);
System.out.println(ex4);

Which JDK version did you use? I tested this on JDK version 1.6.0_21 (trying to keep some support for older stuff) and got a couple `symbol not found` errors. — T145, Feb 12 '14 at 14:42
@T145 check here: http://ideone.com/ZOaLeS (it uses Java 1.7.0_25 but should do fine on Java 6 as well. — Luiggi Mendoza, Feb 12 '14 at 14:46

score 2 · Answer 2 · answered Feb 11 '14 at 15:20

java has no native concept of "ranges", let alone support for them in case statements.

usually, when faced with this kind of logic i personally would do one of 2 things:

just have a chain of if-else statements. doesnt even habe to be a chain:
```
public static double calculateCopyPrice(int copies) {
   if (copies > 1000) return 0.25;
   if (copies >= 750) return 0.26;
   //etc
}
```
this code has no "else" branches and is just as much typing as the switch syntax you'd like. possibly even less (i only check a single bound every time)
you could use an enum, say:
```
public enum Division {UNDER_100, 100_to_500, ... }
```
and then :
```
Division division = categorize(copies);
switch (division) {
   case UNDER_100:
   //etc
}
```
but this is serious overkill for what youre trying to do. i'd use that if this division is also useful elsewhere in your code.

score 1 · Answer 3 · answered Feb 11 '14 at 15:25

Switch case function must have an exact number in case. For example:

case 0:
case 1:

You're trying to use case from some value to some value and it's not implemented that way in Java. For your problem, you must use if-else statement since it's impossible to do it with switch case. Hope it helped.

score 1 · Answer 4 · answered Feb 11 '14 at 15:32

Look the problem is very basic..

In a switch statement it allows only the following datatypes and wrapper classes Byte,short,char,int,Byte,Short,Character,Integer,enum,String..

If you are passing anything other than that will give you an error. In your case the condition which you are evaluating will give you result which is a Boolean value.

score 0 · Answer 5 · answered Oct 27 '15 at 10:36

NavigableMap.seilingEntry() may be a good solution in many cases,
but in other cases the following may be clearer:

double getPrice(int copies){
    return copies>1000 ? 0.25
            : copies>750 ? 0.26
            : copies>500 ? 0.27
            : copies>100 ? 0.28
            : copies>0 ? 0.30
            : 0; // or check this condition first, throwing an exception
}

How are "ranges" defined in Java?

5 Answers5