java迭代器移除元素出现并发修改异常的原因及解决

public class InteratorTest {
 public static void main(String[] args) {
 List<String> list = new ArrayList<>();
 list.add("zhangsan");
 list.add("lisi");
 list.add("wangwu");
 list.add("zhaoliu");
 
 Iterator<String> it = list.iterator();
 while(it.hasNext()) {
 String str = it.next();//java.util.ConcurrentModificationException并发修改异常
 System.out.println(str);
 if("lisi".equals(str)) {
 list.remove(str);
 }
 }
 System.out.println(list);
 }
}

public E next() {
   checkForComodification();//检查迭代器元素修改的次数是否和集合元素修改的此处一样，如果不一样则会抛出并发修改异常
   int i = cursor;
   if (i >= size)
    throw new NoSuchElementException();
   Object[] elementData = ArrayList.this.elementData;
   if (i >= elementData.length)
    throw new ConcurrentModificationException();
   cursor = i + 1;
   return (E) elementData[lastRet = i];
  }

 public void remove() {
   if (lastRet < 0)
    throw new IllegalStateException();
   checkForComodification();
 
   try {
    ArrayList.this.remove(lastRet);//用的还是集合的remove方法
    cursor = lastRet;
    lastRet = -1;
    expectedModCount = modCount;
   } catch (IndexOutOfBoundsException ex) {
    throw new ConcurrentModificationException();
   }
  }

public class InteratorTest {
 public static void main(String[] args) {
 List<String> list = new ArrayList<>();
 list.add("zhangsan");
 list.add("lisi");
 list.add("wangwu");
 list.add("zhaoliu");
 
 Iterator<String> it = list.iterator();
 while(it.hasNext()) {
 String str = it.next();//不会出现并发修改异常
 System.out.println(str);
 if("wangwu".equals(str)) {//用集合Remove方法删除倒数第二个元素
 list.remove(str);
 }
 }
 System.out.println(list);
 }
}

public boolean hasNext() {
   return cursor != size;//根据上面的说法在循环第四次是返回的是false，不会执行循环里的的代码
  }

Map<Integer, String> map = new HashMap<>();
map.put(1, "value 1");
map.put(2, "value 2");
map.put(3, "value 3");
map.put(4, "value 4");
map.put(5, "value 5");

for(Iterator<Integer> iterator = map.keySet().iterator(); iterator.hasNext(); ) {
 Integer key = iterator.next();
 if(key != 1) {
  iterator.remove();
 }
}

// remove by value
map.values().removeIf(value -> !value.contains("1"));
// remove by key
map.keySet().removeIf(key -> key != 1);
// remove by entry / combination of key + value
map.entrySet().removeIf(entry -> entry.getKey() != 1);

default boolean removeIf(Predicate<? super E> filter) {
 Objects.requireNonNull(filter);
 boolean removed = false;
 final Iterator<E> each = iterator();
 while (each.hasNext()) {
  if (filter.test(each.next())) {
   each.remove();
   removed = true;
  }
 }
 return removed;
}