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One-liner to make a read-only list of N copies of a link in Java

I have a link to Callable<V>

, and I want to put it in a list N times to go to ExecutorService.invokeAll(...)

. Is there one liner to accomplish this:

ArrayList<Callable<V>> list = new ArrayList<>(N);
for (int k = 0; k < N; ++k) {
    list.add(x); // x is a reference to Callable<V>
}

Similar to the following line in C ++:

const std::vector<T> list(N, x); // x is an instance of T
+3


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2 answers


Like this:



int N = 8;
Callable<Void> a = null;
List<Callable<Void>> nCopies = Collections.nCopies(N, a);
+7


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Returns an immutable list from the documentation . If it's good, this is the best choice.nCopies()

Alternatively you can use Arrays.fill()

to populate an array with the same value, which you can convert toList 



Arrays.fill(callableArray, x);
List<Callable<V>> list = new ArrayList(Arrays.asList(array));
+1


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