java8 for ,forEach ,lambda forEach , strean forEach , parller stream forEach, Iterator性能对比

java8 for ,forEach ,Iterator，lambda forEach ,lambda  strean forEach , lambda parller stream forEach性能对比

性能结果如下：

lambda parallelStream().forEach() >  lambda stream().forEach() ≈ lambda forEach()  > classical iterator ≈ classical forEach  > classical for

测试代码如下：

 public class ForTest {
     public static void main(String[] args) {
         for( int t=1;t<5;t++){
             for(int tt=1;tt<=4;tt++){
                 List<Integer> testList = Arrays.asList(new Integer[(int) Math.pow(100,(t))]);
                 long t1 = System.currentTimeMillis();
                 for(int i=0;i<testList.size();i++){
                     Integer b = testList.get(i);
                 }
                 long t2 = System.currentTimeMillis();

                 for(Integer i:testList){
                     Integer b = i;
                 }
                 long t3 = System.currentTimeMillis();

                 testList.forEach(integer -> {Integer b = integer;});
                 long t4 = System.currentTimeMillis();

                 testList.stream().forEach(integer -> {Integer b = integer;});
                 long t5 = System.currentTimeMillis();

                 testList.parallelStream().forEach(integer -> {Integer b = integer;});
                 long t6 = System.currentTimeMillis();

                 Integer b;
                 for(Iterator<Integer> iterator = testList.iterator(); iterator.hasNext(); b = iterator.next());
                 long t7 = System.currentTimeMillis();

                 System.out.println("x" + tt +": loop size:" + testList.size());
                 System.out.println("y" + t + ": classical for loop waste millisecond:"+(t2-t1));
                 System.out.println("y" + t + ": classical forEach loop waste millisecond:"+(t3-t2));
                 System.out.println("y" + t + ": lambda forEach loop waste millisecond:"+(t4-t3));
                 System.out.println("y" + t + ": lambda not parallel stream forEach loop waste millisecond:"+(t5-t4));
                 System.out.println("y" + t + ": lambda parallel stream forEach loop waste millisecond:"+(t6-t5));
                 System.out.println("y" + t + ": classical iterator loop waste millisecond:"+(t7-t6)+"\n");
             }
         }
     }
 }

测试结果：

x1: loop size:100
y1: classical for loop waste millisecond:0
y1: classical forEach loop waste millisecond:0
y1: lambda forEach loop waste millisecond:74
y1: lambda not parallel stream forEach loop waste millisecond:2
y1: lambda parallel stream forEach loop waste millisecond:7
y1: classical iterator loop waste millisecond:0

x2: loop size:100
y1: classical for loop waste millisecond:0
y1: classical forEach loop waste millisecond:0
y1: lambda forEach loop waste millisecond:1
y1: lambda not parallel stream forEach loop waste millisecond:0
y1: lambda parallel stream forEach loop waste millisecond:0
y1: classical iterator loop waste millisecond:0

x3: loop size:100
y1: classical for loop waste millisecond:1
y1: classical forEach loop waste millisecond:0
y1: lambda forEach loop waste millisecond:0
y1: lambda not parallel stream forEach loop waste millisecond:1
y1: lambda parallel stream forEach loop waste millisecond:0
y1: classical iterator loop waste millisecond:0

x4: loop size:100
y1: classical for loop waste millisecond:0
y1: classical forEach loop waste millisecond:0
y1: lambda forEach loop waste millisecond:0
y1: lambda not parallel stream forEach loop waste millisecond:0
y1: lambda parallel stream forEach loop waste millisecond:0
y1: classical iterator loop waste millisecond:0

x1: loop size:10000
y2: classical for loop waste millisecond:1
y2: classical forEach loop waste millisecond:0
y2: lambda forEach loop waste millisecond:1
y2: lambda not parallel stream forEach loop waste millisecond:0
y2: lambda parallel stream forEach loop waste millisecond:1
y2: classical iterator loop waste millisecond:1

x2: loop size:10000
y2: classical for loop waste millisecond:1
y2: classical forEach loop waste millisecond:1
y2: lambda forEach loop waste millisecond:0
y2: lambda not parallel stream forEach loop waste millisecond:0
y2: lambda parallel stream forEach loop waste millisecond:1
y2: classical iterator loop waste millisecond:1

x3: loop size:10000
y2: classical for loop waste millisecond:0
y2: classical forEach loop waste millisecond:1
y2: lambda forEach loop waste millisecond:0
y2: lambda not parallel stream forEach loop waste millisecond:0
y2: lambda parallel stream forEach loop waste millisecond:1
y2: classical iterator loop waste millisecond:0

x4: loop size:10000
y2: classical for loop waste millisecond:1
y2: classical forEach loop waste millisecond:0
y2: lambda forEach loop waste millisecond:0
y2: lambda not parallel stream forEach loop waste millisecond:0
y2: lambda parallel stream forEach loop waste millisecond:1
y2: classical iterator loop waste millisecond:0

x1: loop size:1000000
y3: classical for loop waste millisecond:14
y3: classical forEach loop waste millisecond:9
y3: lambda forEach loop waste millisecond:6
y3: lambda not parallel stream forEach loop waste millisecond:8
y3: lambda parallel stream forEach loop waste millisecond:3
y3: classical iterator loop waste millisecond:7

x2: loop size:1000000
y3: classical for loop waste millisecond:17
y3: classical forEach loop waste millisecond:12
y3: lambda forEach loop waste millisecond:7
y3: lambda not parallel stream forEach loop waste millisecond:0
y3: lambda parallel stream forEach loop waste millisecond:1
y3: classical iterator loop waste millisecond:18

x3: loop size:1000000
y3: classical for loop waste millisecond:14
y3: classical forEach loop waste millisecond:19
y3: lambda forEach loop waste millisecond:0
y3: lambda not parallel stream forEach loop waste millisecond:1
y3: lambda parallel stream forEach loop waste millisecond:0
y3: classical iterator loop waste millisecond:17

x4: loop size:1000000
y3: classical for loop waste millisecond:13
y3: classical forEach loop waste millisecond:25
y3: lambda forEach loop waste millisecond:1
y3: lambda not parallel stream forEach loop waste millisecond:0
y3: lambda parallel stream forEach loop waste millisecond:1
y3: classical iterator loop waste millisecond:31

x1: loop size:100000000
y4: classical for loop waste millisecond:237
y4: classical forEach loop waste millisecond:107
y4: lambda forEach loop waste millisecond:73
y4: lambda not parallel stream forEach loop waste millisecond:70
y4: lambda parallel stream forEach loop waste millisecond:28
y4: classical iterator loop waste millisecond:98

x2: loop size:100000000
y4: classical for loop waste millisecond:158
y4: classical forEach loop waste millisecond:92
y4: lambda forEach loop waste millisecond:59
y4: lambda not parallel stream forEach loop waste millisecond:54
y4: lambda parallel stream forEach loop waste millisecond:26
y4: classical iterator loop waste millisecond:66

x3: loop size:100000000
y4: classical for loop waste millisecond:123
y4: classical forEach loop waste millisecond:67
y4: lambda forEach loop waste millisecond:54
y4: lambda not parallel stream forEach loop waste millisecond:52
y4: lambda parallel stream forEach loop waste millisecond:21
y4: classical iterator loop waste millisecond:70

x4: loop size:100000000
y4: classical for loop waste millisecond:201
y4: classical forEach loop waste millisecond:92
y4: lambda forEach loop waste millisecond:54
y4: lambda not parallel stream forEach loop waste millisecond:53
y4: lambda parallel stream forEach loop waste millisecond:23
y4: classical iterator loop waste millisecond:67