java.util.AbstractList.remove 处的 java.lang.UnsupportedOperationException（未知来源）

Question

I have tried below code

String s[]={"1","2","3","4"};  
Collection c=Arrays.asList(s);  
System.out.println(c.remove("1") +"  remove flag");  

System.out.println(" collcetion "+c);  

I was getting

Exception in thread "main" java.lang.UnsupportedOperationException  
at java.util.AbstractList.remove(Unknown Source)  
at java.util.AbstractList$Itr.remove(Unknown Source)  
at java.util.AbstractCollection.remove(Unknown Source)  
at test.main(test.java:26)  

Can anyone help me to solve this issue?

Answer 1

Easy work around is just to pass in the List into an ArrayList 's constructor.

For example:

String valuesInArray[]={"1","2","3","4"};  
List modifiableList = new ArrayList(Arrays.asList(valuesInArray));
System.out.println(modifiableList.remove("1") + "  remove flag");  
System.out.println(" collcetion "+ modifiableList);

Response:

true remove flag

collcetion [2, 3, 4]

Answer 2

Slight correction: no, it's not an unmodifiable Collection. It just doesn't support adding and removing elements, because it is backed by the supplied array and arrays aren't resizeable. But it supports operations like list.set(index, element)

Answer 3

I was having this problem, because I was also initializing my list with Arrays.asList :

 List<String> names = Arrays.asList("a", "b", "c"); 

To solve the problem, I used addAll instead:

List<String> names = new ArrayList<String>();
names.addAll(Arrays.asList("a", "b", "c"));

This way you can edit the list, add new items or remove.

Answer 4

The List returned by Arrays.asList method of java.util.Arrays class is a fixed-size list object which means that elements cannot be added to or removed from the list.

So functions like Adding or Removing cannot be operated on such kind of Lists.

The solution to adding or removing without getting java.lang.UnsupportedOperationException is ->

List<String> strList= new ArrayList<>(Arrays.asList(strs));

//Then Add or Remove can be called on such List

newList.add("100");
newList.remove("100");

Answer 5

一个衬线修复方法是像这样声明您的列表：

List<Integer> list2 = new ArrayList<>(Arrays.asList(0,8,1,5,7,0));

Answer 6

The following method

private void printCollection() {
  List<String> strings = new ArrayList<>(Arrays.asList("1", "2", "3", "4"));

  System.out.println(strings.remove("1") + " remove flag");
  System.out.println("collection " + strings);
}