如何对CopyOnWriteArrayList进行排序 [英] How to sort CopyOnWriteArrayList

问题描述

我想对CopyOnWriteArrayList进行排序。目前它正在抛出未排序的操作异常。

I want to sort CopyOnWriteArrayList. Currently it is throwing unsorted operation exception.

  import java.util.Collections;
  import java.util.List;
  import java.util.concurrent.CopyOnWriteArrayList;

 public class CopyOnWriteArrayListExample {

  public static void main(final String[] args) {
     List<String> list = new CopyOnWriteArrayList<>();
    list.add("3");
    list.add("2");
    list.add("1");

    Collections.sort(list);
   }
}

Exception in thread "main" java.lang.UnsupportedOperationException
at java.util.concurrent.CopyOnWriteArrayList$COWIterator.set(CopyOnWriteArrayList.java:1049)
at java.util.Collections.sort(Collections.java:159)
at com.sac.list.CopyOnWriteArrayListExample.main(CopyOnWriteArrayListExample.java:15)  

提前致谢。

推荐答案

Collections.sort使用ListIterator.set

Collections.sort uses ListIterator.set

    ...
    for (int j=0; j<a.length; j++) {
        i.next();
        i.set((T)a[j]);
    }

但CopyOnWriteArrayList的ListIterator不支持删除，设置或添加方法。

but CopyOnWriteArrayList's ListIterator does not support the remove, set or add methods.

解决方法：

    Object[] a = list.toArray();
    Arrays.sort(a);
    for (int i = 0; i < a.length; i++) {
        list.set(i, (String) a[i]);
    }

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