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By executing below code why i get the java.lang.UnsupportedOperationException

Here is Code.

public static void main(String[] args) {
        List<String> strs = Arrays.asList("One","Two","Three","Four");

        Consumer<String> upperCaseConsumer = s -> strs.add(s.toUpperCase());
        Consumer<String> printConsumer = s -> System.out.println(s);

        strs.forEach(upperCaseConsumer);
        strs.forEach(printConsumer);
}
RBS
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1 Answers1

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Arrays.asList("One","Two","Three","Four") returns a constant size List backed by an array, so you can't add elements to it.

Use 

List<String> strs = new ArrayList<>(Arrays.asList("One","Two","Three","Four"));

instead.

Eran
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  • By Executing List strs = Arrays.asList("One","Two","Three","Four"); System.out.println(strs.getClass().getSimpleName()); it gives me class name ArrayList And By executing List strs = new ArrayList<>(Arrays.asList("One","Two","Three","Four")); System.out.println(strs.getClass().getSimpleName()); it also give me ArrayList so how it makes difference whether i create arraylist by asList or using new ? – RBS Mar 03 '20 at 07:12
  • @RBS It's not the same ArrayList. The former is `java.util.Arrays$ArrayList` and the latter is `java.util.ArrayList` – Eran Mar 03 '20 at 07:15
  • Thanks, i need to read more in details for it. – RBS Mar 03 '20 at 07:18