Perform multiple unrelated operations on elements of a single stream in Java

Question

How can I perform multiple unrelated operations on elements of a single stream?

Say I have a List composed from a text. Each string in the

Answer 1

Here is the answer to address the OP from a different aspect. First of all, let's take a look how fast/slow to iterate a list/collection. Here is the test result on my machine by the below performance test:

When: length of string list = 100, Thread number = 1, loops = 1000, unit = milliseconds

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OP: 0.013

Accepted answer: 0.020

By the counter function: 0.010

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When: length of string list = 1000_000, Thread number = 1, loops = 100, unit = milliseconds

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OP: 99.387

Accepted answer: 89.848

By the counter function: 59.183

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Conclusion: The percentage of performance improvement is pretty small or even slower(if the length of string list is small). generally, it's a mistake to reduce the iteration of list/collection which is loaded in memory by the more complicate collector. you won't get much performance improvements. we should look into somewhere else if there is a performance issue.

Here is my performance test code with tool Profiler: (I'm not going to discuss how to do a performance test here. if you doubt the test result, you can do it again with any tool you believe in)

@Test
public void test_46539786() {
    final int strsLength = 1000_000;
    final int threadNum = 1;
    final int loops = 100;
    final int rounds = 3;

    final List strs = IntStream.range(0, strsLength).mapToObj(i -> i % 2 == 0 ? i + " of " + i : i + " for " + i).toList();

    Profiler.run(threadNum, loops, rounds, "OP", () -> {
        List wordsInStr = strs.stream().filter(t -> t.contains("of")).map(t -> t.split(" ").length).collect(Collectors.toList());
        List linePortionAfterFor = strs.stream().filter(t -> t.contains("for")).map(t -> t.substring(t.indexOf("for")))
                .collect(Collectors.toList());

        assertTrue(wordsInStr.size() == linePortionAfterFor.size());
    }).printResult();

    Profiler.run(threadNum, loops, rounds, "Accepted answer", () -> {
        Splitter collect = strs.stream().collect(Collector.of(Splitter::new, Splitter::accept, Splitter::merge));
        assertTrue(collect.counts.size() == collect.words.size());
    }).printResult();

    final Function counter = s -> {
        int count = 0;
        for (int i = 0, len = s.length(); i < len; i++) {
            if (s.charAt(i) == ' ') {
                count++;
            }
        }
        return count;
    };

    Profiler.run(threadNum, loops, rounds, "By the counter function", () -> {
        List wordsInStr = strs.stream().filter(t -> t.contains("of")).map(counter).collect(Collectors.toList());
        List linePortionAfterFor = strs.stream().filter(t -> t.contains("for")).map(t -> t.substring(t.indexOf("for")))
                .collect(Collectors.toList());

        assertTrue(wordsInStr.size() == linePortionAfterFor.size());
    }).printResult();
}