代码:
- public static void main(String[] args) {
- String[] arr ={"a","b","c"};
- List<String> list = Arrays.asList(arr);
- list.add("d");
- list.add("e");
- }
运行结果:
- Exception in thread "main" java.lang.UnsupportedOperationException
- at java.util.AbstractList.add(AbstractList.java:131)
- at java.util.AbstractList.add(AbstractList.java:91)
- at com.cn.test.main(test.java:11)
修改方法:
List arrayList =new ArrayList(a);
例如:
- public static void main(String[] args) {
- String[] arr ={"a","b","c"};
- List<String> list = Arrays.asList(arr);
- List arrList = new ArrayList(list);
- arrList.add("d");
- arrList.add("e");
- }
原因:
在使用Arrays.asList()后调用add,remove这些method时出现java.lang.UnsupportedOperationException异常。这是由于Arrays.asList() 返回java.util.Arrays$ArrayList, 而不是ArrayList。Arrays$ArrayList和ArrayList都是继承AbstractList,remove,add等method在AbstractList中是默认throw UnsupportedOperationException而且不作任何操作。ArrayList override这些method来对list进行操作,但是Arrays$ArrayList没有override remove(),add()等,所以throw UnsupportedOperationException。