java学习过程的简单记录

Posted 2021-01-13 smilez

1、LinkedList与ArrayList的区别

1）、LinkedList是基于链表的数据结构，ArrayList是实现了基于动态数组的数据结构；

2）、对于查询(get)，ArrayList比LinkedList效率高，因为LinkedList要移动指针

         对于新增(insert)和删除(remove)，LinkedList比ArrayList效率高，因为ArrayList要移动数据

代码如下：

public class ComporeTest {

    private  static Logger logger = LoggerFactory.getLogger(ComporeTest.class);
    private static Integer N = 5000;

    public static Long timeList(List list){
        Long start = System.currentTimeMillis();
        logger.info("start{}",start);
        for(int i = 0; i < N; i++){
            list.add(i);
        }
        logger.info("timeList{}",System.currentTimeMillis() - start);
        return System.currentTimeMillis() - start;
    }

    public static List  addList(List list){
        Object o = new Object();
        for(int i = 0;i < N; i++){
            list.add(0,o);
        }
        logger.info("测试ArrayList与LinkedList的效率");
        return list;
    }

    static Long readList(List list){
        long start = System.currentTimeMillis();
        for(int i = 0; i < list.size(); i++){
            list.get(i);
        }
        return System.currentTimeMillis() - start ;
    }

    public static void main(String [] args){
        logger.info("ArrayList添加"+N+"条消耗时间：{}",timeList(new ArrayList()));
        logger.info("LinkedList添加"+N+"条消耗时间：{}",timeList(new LinkedList()));
        List arrayList = addList(new ArrayList<>()) ;
        List linkedList = addList(new LinkedList<>());
        logger.info("ArrayList查询"+N+"消耗时间：{}",readList(arrayList));
        logger.info("LinkedList查询"+N+"消耗时间：{}",readList(linkedList));
    }
}
测试结果：