Java Unable to add a new list item

Question

I am generating a list from the Registery using the code below.

  List<String> options = Arrays.asList(Advapi32Util.registryGetStringArray(HKEY_LOCAL_MACHINE, key, value)

Later on in the code I want to add to this list However the add method is not working.

The following code below give me an java.lang.unsupportedOperationException.

  options.add("Test");


  Exception in thread "AWT-EventQueue-0" java.lang.UnsupportedOperationException
    at java.util.AbstractList.add(AbstractList.java:148)
    at java.util.AbstractList.add(AbstractList.java:108)

Any ideas.

ldz · Answer 1 · 2019-12-02T22:02:12.510

3

Arrays.asList() returns an immutable list. Instead new ArrayList<>() could be used. The code would then look like follows:

List<String> options = new ArrayList<>(Arrays.asList(
    Advapi32Util.registryGetStringArray(HKEY_LOCAL_MACHINE, key, value)));
options.add("Test");

edited Dec 02 '19 at 22:02

answered Dec 02 '19 at 21:19

ldz

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Thanks let me give that a try. – user1158745 Dec 02 '19 at 21:28
Java doesn't seem to link that. The method add(String) in the type List is not applicable for the arguments (String[]). Is it becuase I am getting it from the reg? – user1158745 Dec 02 '19 at 21:35
I overlooked that the method returns an array. As you can pass collections to the `ArrayList` constructor the only change in your code would be wrapping it with `new ArrayList<>()`. See answer update. – ldz Dec 02 '19 at 22:03

score 0 · Answer 2 · answered Dec 02 '19 at 21:22

0

Arrays.asList creates immutable list which cannot be modified.

answered Dec 02 '19 at 21:22

Mohamed Sweelam

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Java Unable to add a new list item

2 Answers2