java集合遍历性能测试

java version "1.8.0_144"
Java(TM) SE Runtime Environment (build 1.8.0_144-b01)
Java HotSpot(TM) 64-Bit Server VM (build 25.144-b01, mixed mode)

ArrayList LinkedList

Code

import org.junit.Before;
import org.junit.FixMethodOrder;
import org.junit.Test;
import org.junit.runners.MethodSorters;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;

/**
 * ArrayList LinkedList 多种遍历性能测试
 *
 * @author chigusa
 * @function
 * @date 2017/9/25
 */
@FixMethodOrder(MethodSorters.JVM)
public class ListSpeedTest {
    private static final int NUM = 100000;
    private List arrayList;
    private List linkedList;
    private Integer temp;

    @Before
    public void init() {
        arrayList = new ArrayList<>(NUM);
        linkedList = new LinkedList<>();
        for (int i = 0; i < NUM; i++) {
            arrayList.add(Integer.MAX_VALUE);
            linkedList.add(Integer.MAX_VALUE);
        }
    }

    @Test
    public void forArrayList() {
        for (int i = 0; i < NUM; i++) {
            temp = arrayList.get(i);
        }
    }

    @Test
    public void forLinkedList() {
        for (int i = 0; i < NUM; i++) {
            temp = linkedList.get(i);
        }
    }

    @Test
    public void iteratorInArrayList() {
        Iterator iterator = arrayList.iterator();
        while (iterator.hasNext()) {
            temp = iterator.next();
        }
    }

    @Test
    public void iteratorInLinkedList() {
        Iterator iterator = linkedList.iterator();
        while (iterator.hasNext()) {
            temp = iterator.next();
        }
    }

    @Test
    public void forEachArrayList() {
        for (Integer i : arrayList) {
            temp = i;
        }
    }

    @Test
    public void forEachLinkedList() {
        for (Integer i : linkedList) {
            temp = i;
        }
    }

    @Test
    public void java8forEachArrayList() {
        arrayList.forEach(integer -> temp = integer);
    }

    @Test
    public void java8forEachLinkedList() {
        arrayList.forEach(integer -> temp = integer);
    }
}

结果

测试结果

HashMap

Code

import org.junit.Before;
import org.junit.FixMethodOrder;
import org.junit.Test;
import org.junit.runners.MethodSorters;

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

/**
 * HashMap 遍历方法性能测试
 *
 * @author chigusa
 * @function
 * @date 2017/9/25
 */
@FixMethodOrder(MethodSorters.JVM)
public class HashMapTest {
    private static final int NUM = 100000;
    private HashMap hashMap;
    private Integer k, v;

    @Before
    public void init() {
        hashMap = new HashMap<>(NUM);
        for (int i = 0; i < NUM; i++) {
            hashMap.put(i, i);
        }
    }

    @Test
    public void forEachKeySet() {
        for (Integer i : hashMap.keySet()) {
            k = i;
            v = hashMap.get(i);
        }
    }

    @Test
    public void forEachEntitySet() {
        for (Map.Entry entry : hashMap.entrySet()) {
            k = entry.getKey();
            v = entry.getValue();
        }
    }

    @Test
    public void iterator() {
        Iterator> iterator = hashMap.entrySet().iterator();
        while (iterator.hasNext()) {
            Map.Entry entry = iterator.next();
            k = entry.getKey();
            v = entry.getValue();
        }
    }

    @Test
    public void java8ForEach() {
        hashMap.forEach((k, v) -> {
            this.k = k;
            this.v = v;
        });
    }
}

结果

测试结果