Java集合性能测试结果与参考数据不符，请求排查问题

问题背景 #

我们在编程课程中参考了Java集合性能对比的相关资料，自行测试了多种集合及Map的add、contains、remove、clear操作，但测试结果与参考数据差异很大。测试覆盖的集合/Map包括：

• HashSet、TreeSet、LinkedHashSet
• ArrayList、LinkedList
• ArrayDeque、PriorityQueue
• HashMap、TreeMap、LinkedHashMap

我们执行了100次测试并计算平均值，测试代码如下：

import java.util.*;

public class Testing {
    public void initializeAndRun(int testCases){
        Set<Integer> hashSet = new HashSet<>();
        Set<Integer> treeSet = new TreeSet<>();
        Set<Integer> linkedHashSet = new LinkedHashSet<>();
        List<Integer> linkedList = new LinkedList<>();
        List<Integer> arrayList = new ArrayList<>();
        Queue<Integer> priorityQueue = new PriorityQueue<>();
        Queue<Integer> arrayDeque = new ArrayDeque<>();
        Map<Integer, Integer> hashMap = new HashMap<>();
        Map<Integer, Integer> treeMap = new TreeMap<>();
        Map<Integer, Integer> linkedHashMap = new LinkedHashMap<>();



        testSet(hashSet, "Hash Set","add", testCases);
        testSet(treeSet, "Tree Set","add", testCases);
        testSet(linkedHashSet, "Linked Hash Set", "add", testCases);
        testList(linkedList, "Linked List", "add", testCases);
        testList(arrayList, "Array List", "add", testCases);
        testQueue(priorityQueue, "Priority Queue", "add", testCases);
        testQueue(arrayDeque, "Array Deque", "add", testCases);
        testMap(hashMap, "Hash Map", "add", testCases);
        testMap(treeMap, "Tree Map", "add", testCases);
        testMap(linkedHashMap, "Linked Hash Map", "add", testCases);


        System.out.println();

        testSet(hashSet, "Hash Set","contains", testCases);
        testSet(treeSet, "Tree Set","contains", testCases);
        testSet(linkedHashSet, "Linked Hash Set", "contains", testCases);
        testList(linkedList, "Linked List", "contains", testCases);
        testList(arrayList, "Array List", "contains", testCases);
        testQueue(priorityQueue, "Priority Queue", "contains", testCases);
        testQueue(arrayDeque, "Array Deque", "contains", testCases);
        testMap(hashMap, "Hash Map", "contains", testCases);
        testMap(treeMap, "Tree Map", "contains", testCases);
        testMap(linkedHashMap, "Linked Hash Map", "contains", testCases);

        System.out.println();

        testSet(hashSet, "Hash Set","remove", testCases);
        testSet(treeSet, "Tree Set","remove", testCases);
        testSet(linkedHashSet, "Linked Hash Set", "remove", testCases);
        testList(linkedList, "Linked List", "remove", testCases);
        testList(arrayList, "Array List", "remove", testCases);
        testQueue(priorityQueue, "Priority Queue", "remove", testCases);
        testQueue(arrayDeque, "Array Deque", "remove", testCases);
        testMap(hashMap, "Hash Map", "remove", testCases);
        testMap(treeMap, "Tree Map", "remove", testCases);
        testMap(linkedHashMap, "Linked Hash Map", "remove", testCases);

        System.out.println();

        testSet(hashSet, "Hash Set","clear", testCases);
        testSet(treeSet, "Tree Set","clear", testCases);
        testSet(linkedHashSet, "Linked Hash Set", "clear", testCases);
        testList(linkedList, "Linked List", "clear", testCases);
        testList(arrayList, "Array List", "clear", testCases);
        testQueue(priorityQueue, "Priority Queue", "clear", testCases);
        testQueue(arrayDeque, "Array Deque", "clear", testCases);
        testMap(hashMap, "Hash Map", "clear", testCases);
        testMap(treeMap, "Tree Map", "clear", testCases);
        testMap(linkedHashMap, "Linked Hash Map", "clear", testCases);

        System.out.println();

    }

    private void loadSet(Set<Integer> input){
        input.clear();
        Random randInt = new Random();
        for(int i = 0; i < 100000; i++){
            Integer x = randInt.nextInt(100000);
            input.add(x);
        }
    }

    private void loadList(List<Integer> input){
        input.clear();
        Random randInt = new Random();
        for(int i = 0; i < 100000; i++){
            Integer x = Integer.valueOf(randInt.nextInt(100000));
            input.add(x);
        }
    }

    private void loadQueue(Queue<Integer> input){
        input.clear();
        Random randInt = new Random();
        for(int i = 0; i < 100000; i++){
            Integer x = Integer.valueOf(randInt.nextInt(100000));
            input.add(x);
        }
    }

    private void loadMap(Map<Integer, Integer> input){
        input.clear();
        Random randInt = new Random();
        for(int i = 0; i < 100000; i++){
            Integer x = Integer.valueOf(randInt.nextInt(100000));
            input.put(x, x);
        }
    }

    private void testSet(Set<Integer> input, String name, String test, int testNo){
        long totalTime = 0;
        long start = 0;
        long end = 0;
        Random rand = new Random();
        for(int i = 0; i < testNo; i++){
            loadSet(input);
            Integer x = Integer.valueOf(rand.nextInt(10000));
            if(test.equals("add")) {
                start = System.nanoTime();
                input.add(x);
                end = System.nanoTime();
                input.remove(x);
            }else if(test.equals("contains")){
                start = System.nanoTime();
                input.contains(x);
                end = System.nanoTime();
            }else if(test.equals("remove")){
                Object[] array =  input.toArray();
                int index = rand.nextInt(array.length);
                int element = (int) array[index];
                start = System.nanoTime();
                input.remove(element);
                end = System.nanoTime();
                input.add(element);
            }else if(test.equals("clear")){
                start = System.nanoTime();

                input.clear();

                end = System.nanoTime();
            }

            totalTime += end - start;
        }

        long averageTime = totalTime/testNo;

        printResult(name, test, averageTime);
    }

    private void testList(List<Integer> input, String name, String test, int testNo){
        long totalTime = 0;
        long start = 0;
        long end = 0;
        Random rand = new Random();
        for(int i = 0; i < testNo; i++){
            loadList(input);
            Integer x = Integer.valueOf(rand.nextInt(10000));
            if(test.equals("add")) {
                start = System.nanoTime();
                input.add(x);
                end = System.nanoTime();
                input.remove(x);
            }else if(test.equals("contains")){
                start = System.nanoTime();
                input.contains(x);
                end = System.nanoTime();
            }else if(test.equals("remove")){
                Object[] array =  input.toArray();
                int index = rand.nextInt(array.length);
                int element = (int) array[index];
                start = System.nanoTime();
                input.remove(element);
                end = System.nanoTime();
                input.add(element);
            }else if(test.equals("clear")){
                start = System.nanoTime();

                input.clear();

                end = System.nanoTime();
            }

            totalTime += end - start;
        }

        long averageTime = totalTime/testNo;

        printResult(name, test, averageTime);
    }

    private void testQueue(Queue<Integer> input, String name, String test, int testNo){
        long totalTime = 0;
        long start = 0;
        long end = 0;
        Random rand = new Random();
        for(int i = 0; i < testNo; i++){
            loadQueue(input);
            Integer x = Integer.valueOf(rand.nextInt(10000));
            if(test.equals("add")) {
                start = System.nanoTime();
                input.add(x);
                end = System.nanoTime();
                input.remove(x);
            }else if(test.equals("contains")){
                start = System.nanoTime();
                input.contains(x);
                end = System.nanoTime();
            }else if(test.equals("remove")){
                Object[] array =  input.toArray();
                int index = rand.nextInt(array.length);
                int element = (int) array[index];
                start = System.nanoTime();
                input.remove(element);
                end = System.nanoTime();
                input.add(element);
            }else if(test.equals("clear")){
                start = System.nanoTime();

                input.clear();

                end = System.nanoTime();
            }

            totalTime += end - start;
        }

        long averageTime = totalTime/testNo;

        printResult(name, test, averageTime);
    }

    private void testMap(Map<Integer, Integer> input, String name, String test, int testNo){
        long totalTime = 0;
        long start = 0;
        long end = 0;
        Random rand = new Random();
        for(int i = 0; i < testNo; i++){
            loadMap(input);
            Integer x = Integer.valueOf(rand.nextInt(10000));
            if(test.equals("add")) {
                start = System.nanoTime();
                input.put(x, x);
                end = System.nanoTime();
                input.remove(x, x);
            }else if(test.equals("contains")){
                start = System.nanoTime();
                input.containsKey(x);
                end = System.nanoTime();
            }else if(test.equals("remove")){
                Set<Integer> keysSet = input.keySet();
                Integer[] array = new Integer[keysSet.size()];
                keysSet.toArray(array);
                int index = rand.nextInt(array.length);
                int element = (int) array[index];
                start = System.nanoTime();
                input.remove(element);
                end = System.nanoTime();
                input.put(element, element);
            }else if(test.equals("clear")){
                start = System.nanoTime();

                input.clear();

                end = System.nanoTime();
            }

            totalTime += end - start;
        }

        long averageTime = totalTime/testNo;

        printResult(name, test, averageTime);
    }

    private void printResult(String name, String test, long averageTime){
        System.out.printf("%s: %s: %d ns%n", name,test, averageTime);
    }

    public static void main(String[] args){
        Testing test = new Testing();
        int testCases = 100;
        test.initializeAndRun(testCases);
    }
}

测试输出结果 #

Add操作（单位：纳秒） #

Hash Set: add: 225 ns
Tree Set: add: 430 ns
Linked Hash Set: add: 46 ns
Linked List: add: 61 ns
Array List: add: 33 ns
Priority Queue: add: 45 ns
Array Deque: add: 55 ns
Hash Map: add: 40 ns
Tree Map: add: 166 ns
Linked Hash Map: add: 43 ns

Contains操作（单位：纳秒） #

Hash Set: contains: 235 ns
Tree Set: contains: 456 ns
Linked Hash Set: contains: 57 ns
Linked List: contains: 163147 ns
Array List: contains: 45355 ns
Priority Queue: contains: 35929 ns
Array Deque: contains: 53337 ns
Hash Map: contains: 90 ns
Tree Map: contains: 380 ns
Linked Hash Map: contains: 51 ns

Remove操作（单位：纳秒） #

Hash Set: remove: 506 ns
Tree Set: remove: 1236 ns
Linked Hash Set: remove: 150 ns
Linked List: remove: 54833 ns
Array List: remove: 16115 ns
Priority Queue: remove: 31837 ns
Array Deque: remove: 35739 ns
Hash Map: remove: 110 ns
Tree Map: remove: 823 ns
Linked Hash Map: remove: 129 ns

Clear操作（单位：纳秒） #

Hash Set: clear: 32998 ns
Tree Set: clear: 322 ns
Linked Hash Set: clear: 33273 ns
Linked List: clear: 213397 ns
Array List: clear: 24334 ns
Priority Queue: clear: 25343 ns
Array Deque: clear: 45598 ns
Hash Map: clear: 33457 ns
Tree Map: clear: 27 ns
Linked Hash Map: clear: 33289 ns

可以看到，TreeSet的clear操作等结果与课程给出的数据完全不符。我们仅学习Java3周，希望能找到问题所在。

内容的提问来源于stack exchange，提问作者Shakthi Weerawansa