记一次list循环中对其remove报ConcurrentModificationException错踩过的坑

 增强循环：

public static void main(String[] args) {
ArrayList list = Lists.newArrayList(1, 2, 3, 4, 5);
list.forEach(e -> {
if (1 == e) {
System.out.println(e);
list.remove(e);
}
});
System.out.println(list);
}

public static void main(String[] args) {
ArrayList list = Lists.newArrayList(1, 2, 3, 4, 5);
for (Integer e : list) {
if (1 == e) {
System.out.println(e);
list.remove(e);
}
}
System.out.println(list);
}

上面两种代码会包如下错误：

1常规循环：

public static void main(String[] args) {
ArrayList list = Lists.newArrayList(5, 1, 3, 4, 6);
for (int i = 0; i if (1 == list.get(i)) {
System.out.println(list.get(i));
list.remove(i);
}
if (5 == list.get(i)) {
System.out.println(list.get(i));
list.remove(i);
// 或者 list.remove(list.get(i));
}
}
System.out.println(list);
}


注：上面这种方法可以删除元素，但是删除的同时索引在增加，列表的size在减小，导致最后会漏删,比如下面的运行结果1就没有删除掉。这种适合只删除一条数据的情况

2迭代器：

public static void main(String[] args) {
ArrayList list = Lists.newArrayList(5, 1, 3, 4, 6);
Iterator iterator = list.iterator();
while (iterator.hasNext()) {
Integer next = iterator.next();
if (1 == next) {
System.out.println(next);
iterator.remove();
}
if (5 == next) {
System.out.println(next);
iterator.remove();
}
}
System.out.println(list);
}

这种方式可以正常的循环和删除