Problems converting Set of Integers to int[] array

I have no problems converting a Set of Strings to 开发者_如何转开发a string[] array, but I'm having problems doing so with converting a Set of Integer to an int[] array. How can I convert the Integers to its primitive?

I cannot seem to find any related questions. Any quick suggestions that can help?

Sometimes, autoboxing cannot be used, as in the case of arrays. I don't think an array of integers will automatically be converted to an array of ints.

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string[] doesn't exist, I guess you mean String[].

For converting a Set<Integer> to int[] you'd have to iterate over the set manually.

Like this:

Set<Integer> set = ...;

int[] arr = new int[set.size()];

int index = 0;

for( Integer i : set ) {
  arr[index++] = i; //note the autounboxing here
}

Note that sets don't have any particular order, if the order is important, you'd need to use a SortedSet.

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This is why Guava has an Ints.toArray(Collection<Integer>) method, returning int[].

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With java 8:

Set<Integer> set = new HashSet<>(); 
// TODO: Add implement for set

int[] array = set.stream().mapToInt(Integer::intValue).toArray();

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I guess the problem is that Set<Integer>.toArray converts to Integer[], rather than int[]. So you have no simple way: you need to iterate through the set manually and add its elements to the int array. Converting an individual Integer to int is handled by autoboxing in Java 5 and above.

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This should work, assuming auto unboxing!

Set<Integer> myIntegers; // your set
int[] ints = new int[myIntegers.size()];
int index = 0;
for(Integer i : myIntegers){
    ints[index++] = i;
}

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you can call the

Integer.intValue();

function...

lemme know more specifics of what you need :)

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If you use Java 5+ Autoboxing should take care of this...!

What error do you get?

edit: ok i see..

Like other said:

loop on your Set and just put the Integer inside the int[], autoboxing should convert it.