前言:
如今你们对“java collectorstolist”大概比较注意,同学们都需要剖析一些“java collectorstolist”的相关文章。那么小编同时在网上收集了一些关于“java collectorstolist””的相关文章,希望我们能喜欢,我们一起来学习一下吧!天给大家介绍了Java 16中的Stream增强,可以直接通过toList()来转换成List。
主要涉及下面这几种转换方式:
list.stream().toList();list.stream().collect(Collectors.toList());list.stream().collect(Collectors.toUnmodifiableList());
然后,看到有网友评论问:Stream.toList()和Collectors.toList()的区别是什么?哪个性能好?
处理结果的区别,其实上一篇文章和视频里都有说:
Stream.toList()返回的List是不可变List,不能增删改Collectors.toList()返回的是个普通的List,可以增删改Collectors.toUnmodifiableList()返回的List是不可变List,不能增删改
而至于性能的话,今天我们就来测试一下,看看哪个性能更好。
@BenchmarkMode(Mode.All)@Fork(1)@State(Scope.Thread)@Warmup(iterations = 20, time = 1, batchSize = 10000)@Measurement(iterations = 20, time = 1, batchSize = 10000)public class BenchmarkStreamToList { @Benchmark public List<Integer> streamToList() { return IntStream.range(1, 1000).boxed().toList(); } @Benchmark public List<Integer> collectorsToList() { return IntStream.range(1, 1000).boxed().collect(Collectors.toList()); } @Benchmark public List<Integer> streamToList() { return IntStream.range(1, 1000).boxed().toList(); }}
结果报告:
Benchmark Mode Cnt Score Error UnitsBenchmarkStreamToList.collectorsToList thrpt 20 24.422 ± 0.268 ops/sBenchmarkStreamToList.collectorsToUnmodifiableList thrpt 20 22.784 ± 0.599 ops/sBenchmarkStreamToList.streamToList thrpt 20 31.779 ± 1.732 ops/sBenchmarkStreamToList.collectorsToList avgt 20 0.045 ± 0.006 s/opBenchmarkStreamToList.collectorsToUnmodifiableList avgt 20 0.062 ± 0.035 s/opBenchmarkStreamToList.streamToList avgt 20 0.040 ± 0.028 s/opBenchmarkStreamToList.collectorsToList sample 445 0.046 ± 0.002 s/opBenchmarkStreamToList.collectorsToList:collectorsToList·p0.00 sample 0.039 s/opBenchmarkStreamToList.collectorsToList:collectorsToList·p0.50 sample 0.041 s/opBenchmarkStreamToList.collectorsToList:collectorsToList·p0.90 sample 0.057 s/opBenchmarkStreamToList.collectorsToList:collectorsToList·p0.95 sample 0.073 s/opBenchmarkStreamToList.collectorsToList:collectorsToList·p0.99 sample 0.102 s/opBenchmarkStreamToList.collectorsToList:collectorsToList·p0.999 sample 0.150 s/opBenchmarkStreamToList.collectorsToList:collectorsToList·p0.9999 sample 0.150 s/opBenchmarkStreamToList.collectorsToList:collectorsToList·p1.00 sample 0.150 s/opBenchmarkStreamToList.collectorsToUnmodifiableList sample 460 0.044 ± 0.001 s/opBenchmarkStreamToList.collectorsToUnmodifiableList:collectorsToUnmodifiableList·p0.00 sample 0.042 s/opBenchmarkStreamToList.collectorsToUnmodifiableList:collectorsToUnmodifiableList·p0.50 sample 0.044 s/opBenchmarkStreamToList.collectorsToUnmodifiableList:collectorsToUnmodifiableList·p0.90 sample 0.046 s/opBenchmarkStreamToList.collectorsToUnmodifiableList:collectorsToUnmodifiableList·p0.95 sample 0.047 s/opBenchmarkStreamToList.collectorsToUnmodifiableList:collectorsToUnmodifiableList·p0.99 sample 0.051 s/opBenchmarkStreamToList.collectorsToUnmodifiableList:collectorsToUnmodifiableList·p0.999 sample 0.057 s/opBenchmarkStreamToList.collectorsToUnmodifiableList:collectorsToUnmodifiableList·p0.9999 sample 0.057 s/opBenchmarkStreamToList.collectorsToUnmodifiableList:collectorsToUnmodifiableList·p1.00 sample 0.057 s/opBenchmarkStreamToList.streamToList sample 655 0.031 ± 0.001 s/opBenchmarkStreamToList.streamToList:streamToList·p0.00 sample 0.030 s/opBenchmarkStreamToList.streamToList:streamToList·p0.50 sample 0.031 s/opBenchmarkStreamToList.streamToList:streamToList·p0.90 sample 0.032 s/opBenchmarkStreamToList.streamToList:streamToList·p0.95 sample 0.033 s/opBenchmarkStreamToList.streamToList:streamToList·p0.99 sample 0.035 s/opBenchmarkStreamToList.streamToList:streamToList·p0.999 sample 0.037 s/opBenchmarkStreamToList.streamToList:streamToList·p0.9999 sample 0.037 s/opBenchmarkStreamToList.streamToList:streamToList·p1.00 sample 0.037 s/opBenchmarkStreamToList.collectorsToList ss 20 0.043 ± 0.001 s/opBenchmarkStreamToList.collectorsToUnmodifiableList ss 20 0.045 ± 0.004 s/opBenchmarkStreamToList.streamToList ss 20 0.031 ± 0.001 s/op
从报告中我们可以看到:
吞吐量:streamToList > collectorsToList > collectorsToUnmodifiableList平均耗时:streamToList > collectorsToList > collectorsToUnmodifiableListp0.9999耗时:streamToList > collectorsToUnmodifiableList > collectorsToList冷启动耗时:streamToList > collectorsToList > collectorsToUnmodifiableList
所以,Stream.toList()的性能要各方面都要好于Collectors.toList()和Collectors.toUnmodifiableList()。
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本文收录在了我正在连载的《Java新特性专栏》,该系列该用电子书的方式编写,如果想要沉浸式阅读学习的话,可以访问Web版本:
再放大一些数据量,试试:
@Benchmarkpublic List<Integer> streamToList() { return IntStream.range(1, 10000).boxed().toList();}@Benchmarkpublic List<Integer> collectorsToList() { return IntStream.range(1, 10000).boxed().collect(Collectors.toList());}@Benchmarkpublic List<Integer> streamToList() { return IntStream.range(1, 10000).boxed().toList();}
结果报告:
Benchmark Mode Cnt Score Error UnitsBenchmarkStreamToList.collectorsToList thrpt 20 2.186 ± 0.162 ops/sBenchmarkStreamToList.collectorsToUnmodifiableList thrpt 20 2.184 ± 0.042 ops/sBenchmarkStreamToList.streamToList thrpt 20 3.538 ± 0.058 ops/sBenchmarkStreamToList.collectorsToList avgt 20 0.426 ± 0.004 s/opBenchmarkStreamToList.collectorsToUnmodifiableList avgt 20 0.469 ± 0.016 s/opBenchmarkStreamToList.streamToList avgt 20 0.293 ± 0.008 s/opBenchmarkStreamToList.collectorsToList sample 58 0.448 ± 0.049 s/opBenchmarkStreamToList.collectorsToList:collectorsToList·p0.00 sample 0.414 s/opBenchmarkStreamToList.collectorsToList:collectorsToList·p0.50 sample 0.422 s/opBenchmarkStreamToList.collectorsToList:collectorsToList·p0.90 sample 0.458 s/opBenchmarkStreamToList.collectorsToList:collectorsToList·p0.95 sample 0.560 s/opBenchmarkStreamToList.collectorsToList:collectorsToList·p0.99 sample 1.160 s/opBenchmarkStreamToList.collectorsToList:collectorsToList·p0.999 sample 1.160 s/opBenchmarkStreamToList.collectorsToList:collectorsToList·p0.9999 sample 1.160 s/opBenchmarkStreamToList.collectorsToList:collectorsToList·p1.00 sample 1.160 s/opBenchmarkStreamToList.collectorsToUnmodifiableList sample 60 0.458 ± 0.004 s/opBenchmarkStreamToList.collectorsToUnmodifiableList:collectorsToUnmodifiableList·p0.00 sample 0.447 s/opBenchmarkStreamToList.collectorsToUnmodifiableList:collectorsToUnmodifiableList·p0.50 sample 0.455 s/opBenchmarkStreamToList.collectorsToUnmodifiableList:collectorsToUnmodifiableList·p0.90 sample 0.471 s/opBenchmarkStreamToList.collectorsToUnmodifiableList:collectorsToUnmodifiableList·p0.95 sample 0.482 s/opBenchmarkStreamToList.collectorsToUnmodifiableList:collectorsToUnmodifiableList·p0.99 sample 0.492 s/opBenchmarkStreamToList.collectorsToUnmodifiableList:collectorsToUnmodifiableList·p0.999 sample 0.492 s/opBenchmarkStreamToList.collectorsToUnmodifiableList:collectorsToUnmodifiableList·p0.9999 sample 0.492 s/opBenchmarkStreamToList.collectorsToUnmodifiableList:collectorsToUnmodifiableList·p1.00 sample 0.492 s/opBenchmarkStreamToList.streamToList sample 78 0.293 ± 0.012 s/opBenchmarkStreamToList.streamToList:streamToList·p0.00 sample 0.277 s/opBenchmarkStreamToList.streamToList:streamToList·p0.50 sample 0.284 s/opBenchmarkStreamToList.streamToList:streamToList·p0.90 sample 0.309 s/opBenchmarkStreamToList.streamToList:streamToList·p0.95 sample 0.377 s/opBenchmarkStreamToList.streamToList:streamToList·p0.99 sample 0.459 s/opBenchmarkStreamToList.streamToList:streamToList·p0.999 sample 0.459 s/opBenchmarkStreamToList.streamToList:streamToList·p0.9999 sample 0.459 s/opBenchmarkStreamToList.streamToList:streamToList·p1.00 sample 0.459 s/opBenchmarkStreamToList.collectorsToList ss 20 0.474 ± 0.133 s/opBenchmarkStreamToList.collectorsToUnmodifiableList ss 20 0.493 ± 0.099 s/opBenchmarkStreamToList.streamToList ss 20 0.325 ± 0.056 s/op
从报告中我们可以看到
吞吐量:streamToList > collectorsToList > collectorsToUnmodifiableList平均耗时:streamToList > collectorsToList > collectorsToUnmodifiableListp0.9999耗时:streamToList > collectorsToUnmodifiableList > collectorsToList冷启动耗时:streamToList > collectorsToList > collectorsToUnmodifiableList
所以,即使集合内的元素增大,Stream.toList()的性能在各方面依然都要好于Collectors下的方法。
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