Java中List.remove()方法的bug

淡淡的烟草味﹌ 2022-05-28 08:23 202阅读 0赞

一、在Java中List.remove方法有个bug  
1.看第一个针对Object的

boolean remove(Object var1);

看一下API接口，在看一下实现类  
![这里写图片描述][70]  
实现类：

/**
         * {@inheritDoc}
         *
         * <p>This implementation iterates over the collection looking for the
         * specified element.  If it finds the element, it removes the element
         * from the collection using the iterator's remove method.
         *
         * <p>Note that this implementation throws an
         * <tt>UnsupportedOperationException</tt> if the iterator returned by this
         * collection's iterator method does not implement the <tt>remove</tt>
         * method and this collection contains the specified object.
         *
         * @throws UnsupportedOperationException {@inheritDoc}
         * @throws ClassCastException            {@inheritDoc}
         * @throws NullPointerException          {@inheritDoc}
         */
        public boolean remove(Object o) {
            Iterator<E> it = iterator();
            if (o==null) {
                while (it.hasNext()) {
                    if (it.next()==null) {
                        it.remove();
     return true;
                    }
                }
            } else {
                while (it.hasNext()) {
                    if (o.equals(it.next())) {
                        it.remove();
     return true;
                    }
                }
            }
     return false;
        }

2.看第二个针对索引

E remove(int var1);

![这里写图片描述][70 1]  
看一下实现类

/** * {@inheritDoc} * * <p>This implementation always throws an * {@code UnsupportedOperationException}. * * @throws UnsupportedOperationException {@inheritDoc} * @throws IndexOutOfBoundsException {@inheritDoc} */
        public E remove(int index) {
            throw new UnsupportedOperationException();
        }

二、在实际工作中可能会出现的bug  
看一下代码

package net.println.kotlin.chapter4;
    
    import java.util.ArrayList;
    import java.util.List;
    
    /** * @author:wangdong * @description:看一下list的bug */
    public class Bug { 
        public static void main(String[] args) {
            List<Integer> integerList = new ArrayList<>();
            integerList.add(23);
            integerList.add(233);
            integerList.add(243);
            integerList.add(235);
            integerList.add(5);
            integerList.add(50);
            integerList.add(500);
    
            System.out.println(integerList);
            //这里会出现一个bug,当list中存在与索引相同的元素的时候，使用remove，就不知道会删除掉那个了
            integerList.remove(1);
            //这个5的索引是4，这样写可能就删除了索引为5的50，也可能是删除了5的元素
            integerList.remove(5);
            System.out.println(integerList);
    
        }
    }

[70]: /images/20220528/946c3017ffb046e39b6b24fdb2660ce9.png
[70 1]: /images/20220528/773c1971dbf04850b173572d6153bbe3.png