peek | 易学教程

Is there any way to peek at the stdin buffer?

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问题 We know that stdin is, by default, a buffered input; the proof of that is in usage of any of the mechanisms that \"leave data\" on stdin , such as scanf() : int main() { char c[10] = {\'\\0\'}; scanf(\"%9s\", c); printf(\"%s, and left is: %d\\n\", c, getchar()); return 0; } ./a.out hello hello, and left is 10 10 being newline of course... I\'ve always been curious, is there any way to \"peek\" at the stdin buffer without removing whatever may reside there? EDIT A better example might be:

lambda的peek（流元素操作），filter（过滤），map（映射），limit（截断），skip（跳过），collect，distinct（去重）函数使用

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原博地址 @RequestMapping(value = "/list.json", method = GET) public void list(ModelMap modelMap, String taskId, Integer currentPage, Integer pageSize) { Pagination pagination = Pagination.builder().current(currentPage).pageSize(pageSize).build(); if (StringUtils.isNotBlank(taskId)) { return; } Map<Long, TaskBO> taskMap = Maps.newHashMap(); Pager<RecordBO> boPager = recordManager.findRecordList(taskId, pagination); modelMap.addAttribute(KEY_DATA, new Pager<>(pagination, boPager.getList() .stream() .peek(recordBO -> { if (!taskMap.containsKey(recordBO.getTaskId())) { Optional<TaskBO> optionalTaskBO

How to look ahead one element (peek) in a Python generator?

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问题 I can\'t figure out how to look ahead one element in a Python generator. As soon as I look it\'s gone. Here is what I mean: gen = iter([1,2,3]) next_value = gen.next() # okay, I looked forward and see that next_value = 1 # but now: list(gen) # is [2, 3] -- the first value is gone! Here is a more real example: gen = element_generator() if gen.next_value() == \'STOP\': quit_application() else: process(gen.next()) Can anyone help me write a generator that you can look one element forward? 回答1:

阻塞队列 BlockingQueue 常用方法详解

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1、offer()和add()的区别 add()和offer()都是向队列中添加一个元素。但是如果想在一个满的队列中加入一个新元素，调用 add() 方法就会抛出一个 unchecked 异常，而调用 offer() 方法会返回 false。可以据此在程序中进行有效的判断！ 2、peek()和element()的区别 peek()和element()都将在不移除的情况下返回队头，但是peek()方法在队列为空时返回null，调用element()方法会抛出NoSuchElementException异常。 3、poll()和remove()的区别 poll()和remove()都将移除并且返回队头，但是在poll()在队列为空时返回null，而remove()会抛出NoSuchElementException异常。 1、offer()和add()的区别 add()和offer()都是向队列中添加一个元素。但是如果想在一个满的队列中加入一个新元素，调用 add() 方法就会抛出一个 unchecked 异常，而调用 offer() 方法会返回 false。可以据此在程序中进行有效的判断！ 2、peek()和element()的区别 peek()和element()都将在不移除的情况下返回队头，但是peek()方法在队列为空时返回null，调用element(

In Java streams is peek really only for debugging?

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问题 I\'m reading up about Java streams and discovering new things as I go along. One of the new things I found was the peek() function. Almost everything I\'ve read on peek says it should be used to debug your Streams. What if I had a Stream where each Account has a username, password field and a login() and loggedIn() method. I also have Consumer<Account> login = account -> account.login(); and Predicate<Account> loggedIn = account -> account.loggedIn(); Why would this be so bad? List<Account>