如何编码 Stream.findNth()? [英] How to code Stream.findNth()?

问题描述

类似于Stream.findFirst()，有没有办法写Stream.findNth()?

Similar to Stream.findFirst(), is there a way to write Stream.findNth()?

我正在通过重写一些遗留代码来练习 Java 8.而且，我想知道如何使用 Stream API 编写以下函数.

I'm practicing Java 8 by rewriting some legacy code. And, I'm wondering how the below function can be written using Stream API.

static curPipeNumber = 0;

/** skipToEntry() updates 'curPipeNumber' to 'pipeNumber' and returns the first byte position of the word before the ('pipeNumber')-th pipe.
 * It does so by reading and ignoring unnecessary bytes from the buffer.
 * e.g., 
 */
static int skipToEntry(byte[] buf, int len, int nextByteToBeRead, int pipeNumber) {

    if(curPipeNumber == pipeNumber)
        return nextByteToBeRead;

    for(; nextByteToBeRead < len; nextByteToBeRead++) {
        if(buf[nextByteToBeRead] == '|') {
            ++curPipeNumber;
            if(curPipeNumber == pipeNumber) {
                return ++nextByteToBeRead;              
            }
        }
    }

    return nextByteToBeRead;
}

我希望它会转化为:

static int skipToEntry(byte[] buf, int len, int nextByteToBeRead, int pipeNumber) {     
    if(curPipeNumber == pipeNumber)
        return nextByteToBeRead;

    OptionalInt pipeIndex = IntStream.range(i, len)
             .filter(n -> buf[n] == '|')
                 .findNth(pipeNumber);

            curPipeNumber = pipeNumber;
            nextByteToBeRead = pipeIndex.getAsInt() + 1;

    return nextByteToBeRead;
}

推荐答案

OptionalInt result = stream.skip(n-1).findFirst();

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