Java 遍历速度例子。引用。

最新推荐文章于 2025-12-13 12:19:21 发布

转载最新推荐文章于 2025-12-13 12:19:21 发布 · 470 阅读

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本文通过对比ArrayList和LinkedList在使用for循环与迭代器遍历时的性能差异，展示了不同数据结构在Java中的表现。实验中，记录了每种遍历方式所需的时间，并进行了比较。

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

/**
 * IteratorTest
 * @author SageZk
 */
public class IteratorTest {

    public static long testForloops(List<String> list) {
        long start = 0L, end = 0L;
        @SuppressWarnings("unused")
        String le = null;
        start = System.nanoTime();
        for (int i = list.size() - 1; i >= 0; --i) {
            le = list.get(i);
        }
        end = System.nanoTime();
        return end - start;
    }

    public static long testIterator(List<String> list) {
        long start = 0L, end = 0L;
        @SuppressWarnings("unused")
        String le = null;
        start = System.nanoTime();
        Iterator<String> it = list.iterator();
        while (it.hasNext()) {
            le = it.next();
        }
        end = System.nanoTime();
        return end - start;
    }

    public static void main(String[] args) {
        //测试列表长度
        final int LEN = 10000;

        //初始化测试用数据
        List<String> arraylist = new ArrayList<String>();
        List<String> linkedlist = new LinkedList<String>();
        for (int i = 0; i < LEN; ++i) {
            String s = Integer.toString(i, 2);
            arraylist.add(s);
            linkedlist.add(s);
        }

        //打印测试结果
        final String FORMAT = "%1$-16s%2$-16s%3$16d\n";
        System.out.println("List\t\tType\t\tTime(nanoseconds)");
        System.out.println("-------------------------------------------------");
        System.out.printf(FORMAT, "ArrayList", "for", testForloops(arraylist));
        System.out.printf(FORMAT, "ArrayList", "Iterator", testIterator(arraylist));
        System.out.printf(FORMAT, "LinkedList", "for", testForloops(linkedlist));
        System.out.printf(FORMAT, "LinkedList", "Iterator", testIterator(linkedlist));
    }

}