为什么我可以在for-each循环中调用remove？

Question

ArrayList<String> collection = new ArrayList<String>();
collection.add("Apple");
collection.add("Banana");
collection.add("Cherry");
for (String element : collection) 
{
    if (element.equals("Banana")) {
        collection.remove(element);
    }
}

如果这是真的那么为什么上面的代码片段可以正常工作？它不会像我预期的那样抛出并发修改错误。

Answer 1

看两个例子

     // ======  not safe
        List<String> ccollectionNotSafeRemoving = new ArrayList<>();
        ccollectionNotSafeRemoving.add("Apple");
        ccollectionNotSafeRemoving.add("Banana");
        ccollectionNotSafeRemoving.add("Cherry");
        for (String element : ccollectionNotSafeRemoving) 
        {
            // when removing last element will work
            if (element.equals("Banana")) { 
                ccollectionNotSafeRemoving.remove(element);
            }

            // BUT: this won't work ( java.util.ConcurrentModificationException )
            // if (element.equals("Apple")) { 
            //     ccollectionNotSafeRemoving.remove(element);
            // }
        }
        ccollectionNotSafeRemoving.forEach(System.out::println);

      // ====== better
        List<String> collectionSafeRemoving = new ArrayList<>();
        collectionSafeRemoving.add("Apple");
        collectionSafeRemoving.add("Banana");
        collectionSafeRemoving.add("Cherry");
        Iterator<String> iteratorToRemove = collectionSafeRemoving.iterator();
        while (iteratorToRemove.hasNext()) {
           var element = iteratorToRemove.next();
           if (element.equals("Apple")) {
              iteratorToRemove.remove();
           }
        }
        collectionSafeRemoving.forEach(System.out::println);