Java8生成器的无限序列自然数

Question

我用Java8 定义natural了Stream自然数的无限序列()iterator.

IntStream natural = IntStream.iterate(0, i -> i + 1);

natural
 .limit(10)
 .forEach(System.out::println);

现在,我想用Java8定义它generator.

静态流生成(供应商)

什么是最简单的方法？谢谢.

Answer 1

With a generator you need to keep track of your current index. One way would be:

IntStream natural = IntStream.generate(new AtomicInteger()::getAndIncrement);

Note: I use AtomicInteger as a mutable integer rather than for its thread safety: if you parallelise the stream the order will not be as expected.

Answer 2

这内置于IntStream:

IntStream.range(0, Integer.MAX_VALUE)

这将返回所有值(但不包括)Integer.MAX_VALUE.

Answer 3

Note: @assylias managed to do it with a lambda using AtomicInteger. He should probably have the accepted answer.

I'm not sure you can do that with a lambda (because it is stateful), but with a plain Supplier this would work:

IntSupplier generator = new IntSupplier() {
    int current = 0;

    public int getAsInt() {
        return current++;
    }
};

IntStream natural = IntStream.generate(generator);

However, I highly prefer your current solution, because this is the purpose of iterate(int seed, IntUnaryOperator f) IMHO:

IntStream natural = IntStream.iterate(0, i -> i + 1);