java如何获取当前时间戳呢？

获取当前时间戳

//方法1:
System.currentTimeMillis();

//方法2:
Calendar.getInstance().getTimeInMillis();

//方法3:
new Date().getTime();
 

获取时间戳三种方法效率对比

import java.util.Calendar;
import java.util.Date;
public class TimeTest {
    private static long _TEN_THOUSAND=10000;
    public static void main(String[] args) {
        long times=1000*_TEN_THOUSAND;
        long t1=System.currentTimeMillis();
        testSystem(times);
        long t2=System.currentTimeMillis();
        System.out.println(t2-t1);
 
        testCalander(times);
        long t3=System.currentTimeMillis();
        System.out.println(t3-t2);
 
        testDate(times);
        long t4=System.currentTimeMillis();
        System.out.println(t4-t3);
    }
 
    public static void testSystem(long times){ 
        for(int i=0;i<times;i++){
            long currentTime=System.currentTimeMillis();
        }
    }
 
    public static void testCalander(long times){ 
        for(int i=0;i<times;i++){
            long currentTime=Calendar.getInstance().getTimeInMillis();
        }
    }
 
    public static void testDate(long times){
        for(int i=0;i<times;i++){
            long currentTime=new Date().getTime();
        }
    }
}

运行效率对比:
     Calendar.getInstance().getTimeInMillis()速度最慢
    因为Canlendar要处理时区问题会耗费较多的时间