For comparison loop, iterator, java8Stream traverse different flow
1 package cnom.test.testUtils; 2 3 import java.io.Serializable; 4 import java.util.ArrayList; 5 import java.util.Collections; 6 import java.util.Comparator; 7 import java.util.Iterator; 8 import java.util.List; 9 import java.util.Random; 10 11 public class TestCollectionsSort { 12 13 public static void main(String[] args) throws InterruptedException { 14 TestCollectionsSort test = new TestCollectionsSort(); 15 16 List<TestSortModel> list = new ArrayList<TestSortModel>(); 17 TestSortModel model = null; 18 for (int i = 0; i < 8000; i++) { 19 model = test.new TestSortModel(); 20 int intId = (int) (Math.random() * 100); 21 model.setIntId(intId); 22 model.setName("tes" + i); 23 list.add(model); 24 } 25 // JAVA8 使用Comparator排序 26 // list.sort(Comparator.comparing(TestSortModel::getIntId, 27 // Comparator.nullsLast(Comparator.naturalOrder()))); 28 29 List<String> resList = new ArrayList<String>(); 30 31 long t1 = System.currentTimeMillis(); 32 for (TestSortModel tsm : list) { 33 int id = tsm.getIntId(); 34 // Thread.sleep(1); 35 resList.add(tsm.getName()); 36 } 37 System.out.println("增强for循环 遍历耗时：" + (System.currentTimeMillis() - t1) + ";list.size()=" 38 + list.size() + ";list=" + resList.toString()); 39 resList.clear(); 40 41 long t2 = System.currentTimeMillis(); 42 for (int i = 0; i < list.size(); i++) { 43 int id = list.get(i).getIntId(); 44 // Thread.sleep(1); 45 resList.add(list.get(i).getName()); 46 } 47 System.out.println("for循环 遍历耗时：" + (System.currentTimeMillis() - t2) + ";list.size()=" 48 + list.size() + ";list=" + resList.toString()); 49 resList.clear(); 50 51 long t3 = System.currentTimeMillis(); 52 Iterator<TestSortModel> it = list.iterator(); 53 TestSortModel tm = null; 54 while (it.hasNext()) { 55 tm = it.next(); 56 int= ID tm.getIntId (); 57 is // the Thread.sleep (. 1); 58 resList.add (tm.getName ()); 59 } 60 System.out.println ( "Iterator traversal Processed:" + (System. with currentTimeMillis () - T3) + "; list.size () =" 61 is + list.size () + "; List =" + resList.toString ()); 62 is resList.clear (); 63 is 64 // parallerlStream traversal for time-consuming processing business logic. 65 // Note: If added to another list will traverse the elements, then the list must be thread-safe, otherwise the traversal process, two things occur: 66 // 1. The elements of the list will be lost situation; 2. traversal will be thrown: ArrayIndexOutOfBoundsException 67 List <TestSortModel> = listt the Collections.synchronizedList ( new new the ArrayList <TestSortModel> ()); 68 Long T4 = System.currentTimeMillis (); 69 . List.parallelStream () forEach (TSM -> { // if the original list will remain forEachOrdered sequence 70 int ID = tsm.getIntId (); 71 is // listt.add (TSM); // output listt elements have lost, the list is not thread-safe 72 the try { 73 is // the Thread.sleep (. 1) ; 74 resList.add (tsm.getName ()); // resList output will have lost the element 75 } The catch (Exception E) { 76 e.printStackTrace (); 77 } 78 }); 79 the System.out 80 .println ( "list.parallelStream () forEach () traversal Processed:." + (System.currentTimeMillis () - T4) 81 + "; list.size () =" + resList.size () + "; List =" + resList.toString ()); 82 resList.clear (); 83 84 Long T5 = System.currentTimeMillis ( ); 85 . list.stream () forEach (TSM -> { // similar serial execution, and for cycle efficiency, streamlined code 86 int id = tsm.getIntId(); 87 try { 88 // Thread.sleep(1); 89 resList.add(tsm.getName()); 90 } catch (Exception e) { 91 // TODO Auto-generated catch block 92 e.printStackTrace(); 93 } 94 }); 95 System.out.println("list.stream().forEach() 遍历耗时：" + (System.currentTimeMillis() - t5) 96 + ";list.size()=" + list.size() + ";list=" + resList.toString()); 97 resList.clear (); 98 99 Long T6 = System.currentTimeMillis (); 100 list.forEach (TSM -> { // streamline the code, with similar efficiency for loop 101 int ID = tsm.getIntId (); 102 the try { 103 // the Thread.sleep (. 1); 104 resList.add (tsm.getName ()); 105 } the catch (Exception E) { 106 // the TODO Auto-Generated the catch Block 107 e.printStackTrace (); 108 } 109 }) ; 110 System.out.println ( "list.forEach () traversal Processed:" + (System.currentTimeMillis () - T6) 111 + "; list.size () =" + list.size () + "; = List" + resList.toString ()); 112 resList.clear (); 113 114 / ** 115 * for Loop1 enhanced for loop iterates Processed: 80051 1 16 * Processed for loop iterates for Loop2: 80032 117 * Iterator traversal time: 80069 118 . * list.parallelStream () forEach () traversal time: more than 20,101 under-threaded environment, the use of better efficiency when performing time-consuming business logic. 119 . * List.stream () forEach () traversal Processed: 80049 streamline the code 120 * list.forEach () traversal Processed: 80031 121 * / 122 123 } 124 125 public class TestSortModel implements Serializable { 126 127 private static final long serialVersionUID = -890909910704287938L; 128 129 private long longId; 130 131 private int intId; 132 133 private String name; 134 135 public long getLongId() { 136 return longId; 137 } 138 139 public void setLongId(long longId) { 140 this.longId = longId; 141 } 142 143 public int getIntId() { 144 return intId; 145 } 146 147 public void setIntId(int intId) { 148 this.intId = intId; 149 } 150 151 public String getName() { 152 return name; 153 } 154 155 public void setName(String name) { 156 this.name = name; 157 } 158 159 } 160 }