都java1.8了，你还不会遍历`List`时移除元素吗？

1.8之前，如何在遍历List的同时移除元素？没错，就是使用 Iterator迭代器

List<String> list = new ArrayList<>();
list.add("add");
list.add("remove");
Iterator<String> iterator = list.iterator();
String condition = "remove";
while (iterator.hasNext()) {
          
   
    String next = iterator.next();
    if (next.equals(condition)) {
          
   
        iterator.remove();
    }
}

java1.8之后，顶级接口Collection新加入了一个默认方法removeIf，见名知意，就是用来移除符合条件的元素的

/**
     * Removes all of the elements of this collection that satisfy the given
     * predicate.  Errors or runtime exceptions thrown during iteration or by
     * the predicate are relayed to the caller.
     * 移除所以满足filter条件的元素，如果发生了错误，将反馈给调用者
     *
     * @implSpec
     * The default implementation traverses all elements of the collection using
     * its {@link #iterator}.  Each matching element is removed using
     * {@link Iterator#remove()}.  If the collections iterator does not
     * support removal then an {@code UnsupportedOperationException} will be
     * thrown on the first matching element.
     * 默认使用iterator迭代器移除元素，如果集合不支持跌代器模式，就会抛出UnsupportedOperationException（不支持的操作）异常
     *
     * @param filter a predicate which returns {@code true} for elements to be
     *        removed 
     * filter条件为真时，移除当前元素
     * @return {@code true} if any elements were removed
     * 如果元素被移除成功，将返回真
     * @throws NullPointerException if the specified filter is null
     * filter断言如果为空，抛出NullPointerException（空指针）异常
     * @throws UnsupportedOperationException if elements cannot be removed
     *         from this collection.  Implementations may throw this exception if a
     *         matching element cannot be removed or if, in general, removal is not
     *         supported.
     * @since 1.8
     */
    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;
    }

代码实现：

List<String> list = new ArrayList<>();
list.add("add");
list.add("remove");
String condition = "remove";
list.removeIf(e -> e.equals(condition));