Java中LinkedList的fori和foreach效率比较

最新推荐文章于 2022-11-10 03:00:00 发布

dhu86380

最新推荐文章于 2022-11-10 03:00:00 发布

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文章标签： java

原文链接：http://www.cnblogs.com/acode/p/6497024.html

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在《Java中ArrayList的fori和foreach效率比较》中对ArrayList的两种循环方式进行了比较，本次对LinkedList的两种遍历方式进行效率的比较。

1. list的元素为自定义的对象

自定义的Student类

public class Student {

    private String name;

    private Integer age;

    public Student(String name, Integer age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public Integer getAge() {
        return age;
    }
}

【代码实例1】

    public static void main(String[] args) {
        List<Student> list = new LinkedList<Student>();
        int maxNum = 100000;
        for (int i = 0; i < maxNum; i++) {
            list.add(new Student("student" + i, i));
        }

        //开始测试不同方式的for性能
        int listSize = list.size();
        String searchName = "student666";
        boolean searchFlag = false;

        //基本形式的for循环
        long startTime1 = System.currentTimeMillis();
        for (int i = 0; i < listSize; i++) {
            Student val = list.get(i);
            if (searchName.equals(val.getName())) {
                searchFlag = true;
            }
        }
        long endTime1 = System.currentTimeMillis();

        //foreach形式
        long startTime2 = System.currentTimeMillis();
        for (Student stu : list) {
            if (searchName.equals(stu.getName())) {
                searchFlag = true;
            }
        }
        long endTime2 = System.currentTimeMillis();

        //输出运行时间
        System.out.println("fori: " + (endTime1 - startTime1));
        System.out.println("forearch: " + (endTime2 - startTime2));

    }

【运行结果】

fori: 28628
forearch: 10

2. list元素为Integer

【代码实例2】

    public static void main(String[] args) {
        List<Integer> list = new LinkedList<Integer>();
        int maxNum = 10000;
        for (int i = 0; i < maxNum; i++) {
            list.add(i);
        }

        //开始测试不同方式的for性能
        int listSize = list.size();
        Integer searchVal = 66666;
        boolean searchFlag = false;

        //基本形式的for循环
        long startTime1 = System.currentTimeMillis();
        for (int i = 0; i < listSize; i++) {
            Integer val = list.get(i);
            if (searchVal.equals(val)) {
                searchFlag = true;
            }
        }
        long endTime1 = System.currentTimeMillis();

        //foreach形式
        long startTime2 = System.currentTimeMillis();
        for (Integer val : list) {
            if (searchVal.equals(val)) {
                searchFlag = true;
            }
        }
        long endTime2 = System.currentTimeMillis();

        //输出运行时间
        System.out.println("fori: " + (endTime1 - startTime1));
        System.out.println("forearch: " + (endTime2 - startTime2));

    }