測試代碼

package hello.test;

import org.openjdk.jmh.annotations.*;

import org.openjdk.jmh.runner.Runner;

import org.openjdk.jmh.runner.RunnerException;

import org.openjdk.jmh.runner.options.Options;

import org.openjdk.jmh.runner.options.OptionsBuilder;

import java.util.Arrays;

import java.util.concurrent.TimeUnit;

@BenchmarkMode(Mode.Throughput)

@OutputTimeUnit(TimeUnit.MILLISECONDS)

@State(Scope.Thread)

public class BenchmarkTest {

public static final String[] BRAND_ARRAY = {"iphone", "huawei", "xiaomi", "samsung", "vivo", "bbk", "oppo", "meizu", "sony", "xperia", "htc", "oneplus", "smartisan", "lenovo", "gionee", "nubia", "letv", "vertu"};

private static final String bidRequestModel = "oneplus";

@Benchmark

public static String findBidrequstBrandByStream() {

final String lowBidRequestModel = bidRequestModel.toLowerCase();

return Arrays.stream(BRAND_ARRAY).filter(x -> lowBidRequestModel.contains(x)).findAny().get();

}

@Benchmark

public static String findBidrequstBrandByParallelStream() {

final String lowBidRequestModel = bidRequestModel.toLowerCase();

return Arrays.stream(BRAND_ARRAY).parallel().filter(x -> lowBidRequestModel.contains(x)).findAny().get();

}

@Benchmark

public static String findBidrequstBrandByArray() {

final String lowBidRequestModel = bidRequestModel.toLowerCase();

for (String e : BRAND_ARRAY) {

if (lowBidRequestModel.contains(e)) {

return e;

}

}

return "";

}

public static void main(String[] args) throws RunnerException {

Options opt = new OptionsBuilder()

.include(BenchmarkTest.class.getSimpleName())

.forks(1)

.warmupIterations(5)

.measurementIterations(5)

.build();

new Runner(opt).run();

}

}

結果

Benchmark Mode Cnt Score Error Units

BenchmarkTest.findBidrequstBrandByArray thrpt 5 11206.177 ± 1438.816 ops/ms

BenchmarkTest.findBidrequstBrandByParallelStream thrpt 5 206.097 ± 95.776 ops/ms

BenchmarkTest.findBidrequstBrandByStream thrpt 5 4838.695 ± 368.454 ops/ms

總結

對性能敏感的程序, 建議還是用回傳統的for循環

并行流并不一定會比順序流快

java 8 的流式api, 一般情況下比不上傳統的 for 循環

總結

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