How do you use an enum for an array subscript?
enum {VALUE_ONE, ... , SIZE};
int[] x = new int[SIZE];
5 Answers
Here's the code. It doesn't look like good practice, though.
int[] x = new int[EnumClass.values().length];
You can then access the element by ordinal()
int val = x[enumVar.ordinal()];
Still doesn't look like good practice.
Consider using Map<EnumClass, AtomicInteger> like EnumMap<EnumClass, AtomicInteger>. Why atomic integer? because it can have it's value modified instead of assigning a new instance all the time (at the cost of possibly unnecessary synchronization). That's a different issue though.
1 Comment
Dariusz
I don't know what you wan't to achieve.
Map<Enum, AtomicInteger>? You have EnumMap designed for enums. I would not depend on enum's ordinal value for any data structure, since it depends entirely on the definition order. Suppose you save the array, modify the enum, and try to read the array. It'll be a problem.Use an EnumMap - it was intended for just this case.
enum Value {
VALUE_ONE, ... , VALUE_LAKH
}
Map<Value, Integer> x = new EnumMap<>();
x.put(Value.VALUE_ONE, 13);
Internally uses an array (Integer[]). The only disadvantage is using Integer instead of int. And assumedly java 9 or 10 will introduce primitive generic types (List<int> and such).
BTW EnumSet exists too, and is as efficient as BitSet.
Comments
Enum is not number. But you can do SIZE.ordinal()
Comments
For below enum
enum test{VALUE_ONE, ... , SIZE};
Use SIZE like this
int[] x = new int[test.SIZE.ordinal()];
Comments
You can use: int[] x = new int[SIZE.ordinal()]; int var = x[SOME_VALUE.ordinal()];
Its position in its enum declaration, where the initial constant is assigned an ordinal of zero.
Or set special number for each enum elements. like:
enum A {
VALUE_ONE(0),
SIZE(1),
;
int value;
private A( int value) {
this.value = value;
}
public int getValue() {
return this.value;
}
}
int[] x = new int[A.SIZE.getValue()];
int var = x[A.VALUE_ONE.getValue()];
5 Comments
Shadow
When i try System.out.println( x[A.VALUE_ONE.getValue()] ); I get arrayOutOfBoundIndexException
Shadow
VALUE_ONE(0), VALUE_TWO(1), I used these but they both resulted in 0 when printed when SIZE(2)
WidWing
int[] x = new int[A.SIZE.getValue()]; int var1 = x[A.VALUE_ONE.getValue()];// var1 == 0 int var2 = x[A.VALUE_TWO.getValue()];// var2 == 0 You mean that?Shadow
I set
var = x[A.VALUE_ONE.getValue()] and then printed var. I set var equal to the same thing but VALUE_TWO this time and they both printed out 0WidWing
did you fill array x? by default arrays fill with zero. your array is represented as
[0, 0]
values()to get all its values.and useordinal()to get it's position in enum.