Java Commons Collections removeAll [英] Java Commons Collections removeAll

问题描述

CollectionUtils :: removeAll（）Commons Collections 3.2.1

我必须疯了，因为看起来这个方法是做什么的文档状态：

删除从集合中移除的元素。也就是说，此方法返回一个包含c中所有不在remove中的元素的集合。

这个小JUnit测试

  @Test 
 public void testCommonsRemoveAll（）throws Exception {
 String str1 =foo; 
 String str2 =bar; 
 String str3 =qux; 
 
 List< String> collection = Arrays.asList（str1，str2，str3）; 
 System.out.println（collection：+ collection）; 
 
 List< String> remove = Arrays.asList（str1）; 
 System.out.println（remove：+ remove）; 
 
集合result = CollectionUtils.removeAll（collection，remove）; 
 System.out.println（result：+ result）; 
 assertEquals（2，result.size（））; 
} 
  

失败

< blockquote>

java.lang.AssertionError：expected：< 2>但是：< 1>

并打印

 集合：[foo，bar，qux] 
 remove：[foo] 
 result ：[foo] 
  

从我阅读的文档，我应该期望 [bar ，qux] 。

解决方案

编辑2014年1月1日 Apache Commons Collections 4.0终于发布2013年11月21日，并包含此问题的修正。

链接到 CollectionUtils.java

有问题的行（1688 - 1691），并确认该方法之前已损坏：

  / * 
。 .. 
 * @since 4.0（方法存在于3.2，但是完全折断）
 * / 
 public static< E>集合< E> removeAll（final Collection< E> collection，final Collection<？> remove）{
 return ListUtils.removeAll（collection，remove）; 
} 
  

---

不，你不疯了。 removeAll（）实际上（不正确）调用 retainAll（）。

这是 CollectionUtils 中的一个错误，影响版本3.2。已修复，但只在4.0分支中。

https://issues.apache.org/jira/browse/COLLECTIONS-349

作为进一步的证明，这里有一个指向源代码的链接： / p>

http://svn.apache.org/repos/asf/commons/proper/collections/tags/COLLECTIONS_3_2/src/java/org/apache/commons/collections/CollectionUtils.java

查看此行：

  removeAll（Collection collection，Collection remove）{
 return ListUtils.retainAll（collection，remove）; 
} 
  

是的...破碎！

CollectionUtils::removeAll() Commons Collections 3.2.1

I must be going crazy, becuase it seems like this method is doing the inverse of what the docs state:

Removes the elements in remove from collection. That is, this method returns a collection containing all the elements in c that are not in remove.

This little JUnit test

@Test
public void testCommonsRemoveAll() throws Exception {
    String str1 = "foo";
    String str2 = "bar";
    String str3 = "qux";

    List<String> collection = Arrays.asList(str1, str2, str3);
    System.out.println("collection: " + collection);

    List<String> remove = Arrays.asList(str1);
    System.out.println("remove: " + remove);

    Collection result = CollectionUtils.removeAll(collection, remove);
    System.out.println("result: " + result);
    assertEquals(2, result.size());
}

Is failing with

java.lang.AssertionError: expected:<2> but was:<1>

and prints

collection: [foo, bar, qux] 
remove: [foo] 
result: [foo]

From my reading of the docs I should expect [bar, qux]. What have I missed?

解决方案

Edit January 1, 2014 Apache Commons Collections 4.0 was finally released on November 21, 2013, and contains a fix for this issue.

Link to CollectionUtils.java

Lines in question (1688 - 1691), with acknowledgement the method was previously broken:

/*
 ...
 * @since 4.0 (method existed in 3.2 but was completely broken)
 */
public static <E> Collection<E> removeAll(final Collection<E> collection, final Collection<?> remove) {
    return ListUtils.removeAll(collection, remove);
}

---

Original Answer

Nope, you're not crazy. removeAll() is actually (incorrectly) calling retainAll().

This is a bug in CollectionUtils, affecting version 3.2. It's been fixed, but only in the 4.0 branch.

https://issues.apache.org/jira/browse/COLLECTIONS-349

And as further proof, here's a link to the source code:

http://svn.apache.org/repos/asf/commons/proper/collections/tags/COLLECTIONS_3_2/src/java/org/apache/commons/collections/CollectionUtils.java

Check out this line:

public static Collection removeAll(Collection collection, Collection remove) {
    return ListUtils.retainAll(collection, remove);
}

Yep...broken!

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