stream()和parallelStream()测试

àì夳堔傛蜴生んèń 2022-12-29 01:41 116阅读 0赞

测试一

public class SteamTest {
    
        public static void main(String[] args) {
            List<String> list1 = new Random().ints().limit(100).mapToObj(i -> "asdd"+i).distinct().collect(Collectors.toList());
            SteamTest test = new SteamTest();
            test.Test1(list1);
            test.Test2(list1);
        }
    
        public void Test1(List<String> list1){
            Map<String,Object> str = new HashMap();
            Long time = System.currentTimeMillis();
            list1.parallelStream().forEach(s -> {
                str.put(s,getString(s));
            });
            System.out.println("parallelStream运行结束，耗时："+(System.currentTimeMillis()-time));
    
            System.out.println(str.keySet().size());
    
        }
        public void Test2(List<String> list1){
            Map<String,Object> str = new HashMap();
            Long time = System.currentTimeMillis();
            list1.stream().forEach(s -> {
                str.put(s,getString(s));
            });
            System.out.println("stream运行结束，耗时："+(System.currentTimeMillis()-time));
            System.out.println(str.keySet().size());
        }
        public String getString(String str){
    
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            return str+"str";
        }
    }
    //结果
    //parallelStream运行结束，耗时：1414
    //86
    //stream运行结束，耗时：10053
    //100

测试二

public void Test1(List<String> list1){
            Map<String,Object> str = new HashMap();
            Long time = System.currentTimeMillis();
            list1.parallelStream().forEach(System.out::println);
            System.out.println("parallelStream运行结束，耗时："+(System.currentTimeMillis()-time));
        }
        public void Test2(List<String> list1){
            Map<String,Object> str = new HashMap();
            Long time = System.currentTimeMillis();
            list1.stream().forEach(System.out::println);
            System.out.println("stream运行结束，耗时："+(System.currentTimeMillis()-time));
        }
    //结果
    //parallelStream运行结束，耗时：9
    //stream运行结束，耗时：3

测试3

public void Test1(List<String> list1){
            Map<String,Object> str = new HashMap();
            Long time = System.currentTimeMillis();
            list1.parallelStream().forEach(s -> {
                sleepTest(1);
            });
            System.out.println("parallelStream运行结束，耗时："+(System.currentTimeMillis()-time));
    
        }
        public void Test2(List<String> list1){
            Map<String,Object> str = new HashMap();
            Long time = System.currentTimeMillis();
            list1.stream().forEach(s -> {
                sleepTest(2);
            });
            System.out.println("stream运行结束，耗时："+(System.currentTimeMillis()-time));
        }
        public String getString(String str){
    
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            return str+"str";
        }
        public void sleepTest(int i){
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(i);
        }
    //1输出100次
    //parallelStream运行结束，耗时：1315
    //2输出100次
    //stream运行结束，耗时：10055

1.parallelStream 并行流 线程不安全  数据丢失 执行耗时业务速度大于steam

2.stream 串行流 线程安全 数据不会丢失 执行耗时业务速度慢  非耗时业务速度大于parallelStream

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