iterable | 易学教程

java.lang.Iterable error - What does this mean and how do I fix it?

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问题 I've been trying to find an answer to this for a couple days now and have had no luck. It is very late and I am very tired so I thought I would put it up here and hope that someone out there can help. Here is my snippit of code that is popping an error in Eclipse. private void filterByTitle() { String title = Validator.getLine(sc, "Enter the Title to retrieve: "); System.out.println("\n" + Book.getHeadings()); for(Book book : bookList.filterListByTitle(title)) { System.out.println(book); } }

python make class iterable by returning embedded iterable

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问题 I have a class in python, which has an iterable as instance variable. I want to iterate the instances of the class by iterating over the embedded iterable. I implemented this as follows: def __iter__(self): return self._iterable.__iter__() I don't really feel that comfortable calling the __iter__() method on the iterable, as it is a special method. Is this how you would solve this problem in python or is there a more elegant solution? 回答1: The "best" way to way to delegate __iter__ would be:

Collection及其师傅Iterable

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【推荐】2019 Java 开发者跳槽指南.pdf(吐血整理) >>> 上一节我们缕清了Collection家族的关系，接下来我们就来看看这个家族的创始者及其师傅。 1. 师傅Iterable Iterable是一个接口类，先看看接口里面的方法：其中第二个和第三个方法，都是java8新增的，看源码会发现，java8后，可以在接口里面定义默认（关键字default）的方法（必须实现，可以空实现），而且实现类中还可以重写default方法，这样一来有点类似抽象类，只不过接口类用来授艺，抽象类用来遗传。最终给我们代码的迭代带来很大便利。 Iterable里面最主要的当然迭代器Iterator，Iterator本身是接口，这么说来接口师傅（水平有限）传授的都是大道的终极要义，功夫还是得弟子苦练。后来师傅能力提升（java8来了），可以给弟子大道的精华（default方法），让弟子可以毫不费力直接领悟，甚至弟子还可以加以创新（重写），但是要注意多接口实现造成的默认方法冲突问题（冲突很容易解决，就不多说）。关于Iterator在子类的实现可以查看ArrayList源码，很简单，只是大家用得多的是next()方法，不知有没有注意到previous()方法。值得一提的是在Iterator接口里面新增了默认方法：forEachRemaining方法，允许传入一个行为

Resetting Iterable Object

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问题 I am writing a MR job where in the reducer side, I need to check the size of Iterable before doing anything. Someone did asked the same question long back(How to find the size of an Iterable Object?) but the solutions given are not working.Since the Iterable doesnt have a size() method, please suggesst me how to do it. I tried the following options. Tried to get a iterator object from iterable, but got following typecast error. Same error with ResettableIterator. java.lang.ClassCastException:

Treat a java.lang.Iterable as a #list expression in Freemarker

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问题 I have a java.lang.Iterable (in fact, a com.google.gson.JsonArray instance). I would like to enumerate the items in the list using freemarker (2.3.16). [#assign sports = controller.sports] [#-- At this point, sports is bound to a com.google.gson.JsonArray instance. --] [#list sports as sport] ${sport_index} [/#list] I would like to avoid having to write a custom bean and Gson deserializer just to have an explicit collection of items. Using Gson (which already deserializes the JSON string to a

class with iter assigned in constructor not recognized as iterator

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问题 Kind of a weird question about iterators. While investigating a different question, I found the following. Here is an iterable that works: class CacheGen(object): def __init__(self, iterable): if isinstance(iterable, (list, tuple, dict)): self._myiter = iterable else: self._myiter = list(iterable) def __iter__(self): return self._myiter.__iter__() def __contains__(self, key): return self._myiter.__contains__(key) def __getitem__(self, key): return self._myiter.__getitem__(key) Here is a

Best way to convert Iterable<Character> to String?

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问题 What's the easiest/fastest way to convert an Iterable<Character> to a String of the characters from the Iterable? For example, how to convert an Iterable of "A" , "B" , and "C" , to a String "ABC" ? The iter.toString() returns a String "[A, B, C]" . 回答1: 5 Versions: 1) Java 8 streams collecting via StringBuilder.append() : public static String streamAppend(Iterable<Character> chars){ return StreamSupport.stream(chars.spliterator(), true) .collect( StringBuilder::new, StringBuilder::append,

Why there is no getFirst(iterable) method?

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问题 Iterables present two methods for getLast public static <T> T getLast(Iterable<T> iterable); public static <T> T getLast(Iterable<T> iterable, @Nullable T defaultValue); but only one for getFirst public static <T> T getFirst(Iterable<T> iterable, @Nullable T defaultValue); Is there are any design/implementation reason for breaking symmetry? 回答1: I think the point is that there is no reason for a getFirst(iterable) in that this could be done with iterable.iterator().next() . Guava makes an

main loop 'builtin_function_or_method' object is not iterable

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问题 I get this error "main loop 'builtin_function_or_method' object is not iterable" when I run the code below: I have search stackoverflow, but cant find a answer to my question... I have checked for typos, but cant find any error. Please help me! import urllib2 import time import datetime stocksToPull = 'AAPL','GOOG','MSFT','CMG','AMZN','EBAY','TSLA' def pullData(stock): try: print 'Currently pulling',stock print str(datetime.datetime.fromtimestamp(time.time()).strftime('%Y-%m-%d %H:%M:%S'))

What is the Iterable interface used for?

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问题 I am a beginner and I cannot understand the real effect of the Iterable interface. 回答1: Besides what Jeremy said, its main benefit is that it has its own bit of syntactic sugar: the enhanced for-loop. If you have, say, an Iterable<String> , you can do: for (String str : myIterable) { ... } Nice and easy, isn't it? All the dirty work of creating the Iterator<String> , checking if it hasNext() , and calling str = getNext() is handled behind the scenes by the compiler. And since most collections