如何使用 Java 8 流迭代 x 次？
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How to iterate x times using Java 8 stream?
提问by AlikElzin-kilaka
I have an old style forloop to do some load tests:
我有一个旧式for循环来做一些负载测试：
For (int i = 0 ; i < 1000 ; ++i) {
if (i+1 % 100 == 0) {
System.out.println("Test number "+i+" started.");
}
// The test itself...
}
How can I use new Java 8 stream API to be able to do this without the for?
我怎样才能使用新的 Java 8 流 API 来做到这一点，而无需for?
Also, the use of the stream would make it easy to switch to parallel stream. How to switch to parallel stream?
此外，使用流可以很容易地切换到并行流。如何切换到并行流？
* I'd like to keep the reference to i.
* 我想保留对i.
采纳答案by Andrew Tobilko
IntStream.range(0, 1000)
/* .parallel() */
.filter(i -> i+1 % 100 == 0)
.peek(i -> System.out.println("Test number " + i + " started."))
/* other operations on the stream including a terminal one */;
If the test is running on each iteration regardless of the condition (take the filterout):
如果测试在每次迭代中运行而不管条件如何（filter取出）：
IntStream.range(0, 1000)
.peek(i -> {
if (i + 1 % 100 == 0) {
System.out.println("Test number " + i + " started.");
}
}).forEach(i -> {/* the test */});
Another approach (if you want to iterate over an index with a predefined step, as @Tunakimentioned) is:
另一种方法（如果您想使用预定义的步骤迭代索引，如@Tunaki所述）是：
IntStream.iterate(0, i -> i + 100)
.limit(1000 / 100)
.forEach(i -> { /* the test */ });
There is an awesome overloaded method Stream.iterate(seed, condition, unaryOperator)in JDK 9 which perfectly fits your situation and is designed to make a stream finite and might replace a plain for:
Stream.iterate(seed, condition, unaryOperator)JDK 9 中有一个很棒的重载方法，它非常适合您的情况，旨在使流有限并可能替换普通的for：
Stream<Integer> stream = Stream.iterate(0, i -> i < 1000, i -> i + 100);
回答by developer
You can use IntStreamas shown below and explained in the comments:
您可以使用IntStream如下所示并在评论中解释：
(1) Iterate IntStreamrange from 1 to 1000
(1) 迭代IntStream范围从 1 到 1000
(2) Convert to parallelstream
(2) 转换为parallel流
(3) Apply Predicatecondition to allow integers with (i+1)%100 == 0
(3) 应用Predicate条件以允许整数(i+1)%100 == 0
(4) Now convert the integer to a string "Test number "+i+" started."
(4) 现在将整数转换为字符串 "Test number "+i+" started."
(5) Output to console
(5) 输出到控制台
IntStream.range(1, 1000). //iterates 1 to 1000
parallel().//converts to parallel stream
filter( i -> ((i+1)%100 == 0)). //filters numbers & allows like 99, 199, etc..)
mapToObj((int i) -> "Test number "+i+" started.").//maps integer to String
forEach(System.out::println);//prints to the console
