如何从Java中的集合中弹出项目？ [英] How to pop items from a collection in Java?

问题描述

在JDK或apache commons中有一个方法来弹出一个来自java.util.List的元素列表吗？我的意思是，删除元素列表并返回它，像这样的方法：

  public Collection pop（Collection elementsToPop，Collection elements） {
 
 Collection popped = new ArrayList（）; 
 
 for（Object object：elementsToPop）{
 if（elements.contains（object））{
 elements.remove（object）; 
 popped.add（object）; 
} 
} 
 
 return popped; 
} 
  

解决方案

一个堆栈式结构我建议接受 Deque （ LinkedList 是最常见的实现）而不是 Collection 。

如果你实际上不需要把它当作栈，只需从 Collection 并使用 remove（）方法：

  for（Iterator< SomeType> it = elements.iterator（）; it.hasNext（）;）{
 SomeType e = it.next（）; 
 it.remove（）; 
 popped.add（e）; 
} 
  

请注意，remove是一个可选操作， code> UnsupportedOperationException （例如，从 Collections.unmodifiable ...（）的集合返回的迭代器将会）。

编辑：仔细查看您的问题后，我认为您只需要：

  elements.removeAll（elementsToRemove）; 
  

如果你的要点是你需要准确知道 popped，我想你卡住你的原始代码。

Is there a method in JDK or apache commons to "pop" a list of elements from a java.util.List? I mean, remove the list of elements and return it, like this method:

public Collection pop(Collection elementsToPop, Collection elements) {

  Collection popped = new ArrayList();

  for (Object object : elementsToPop) {
    if (elements.contains(object)) {
      elements.remove(object);
      popped.add(object);
    }
  }

  return popped;
}

解决方案

If you're looking for a stack-like structure I suggest accepting a Deque (LinkedList is the most common implementation) instead of a Collection.

If you don't actually need to treat it as a stack, just get an iterator from the Collection and use the remove() method:

for (Iterator<SomeType> it = elements.iterator(); it.hasNext(); ) {
    SomeType e = it.next();
    it.remove();
    popped.add(e);
}

Do note that remove is an optional operation, and some implementations may throw an UnsupportedOperationException (for example, the iterator returned by a Collection from Collections.unmodifiable...() will).

Edit: After looking more closely at your question, I think you just need this:

elements.removeAll(elementsToRemove);

If your main point is you need to know exactly which elements were actually popped, I think you're stuck with your original code.

这篇关于如何从Java中的集合中弹出项目？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！