Java Date 使用

获取当前时间

@Test
public void dateTest(){
    Date date = new Date();
}

字符串和Date互转

@Test
public void date2String(){
    Date date = new Date();
    SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
    String str = simpleDateFormat.format(date);
}

@Test
public void string2Date() throws Exception{
    String str = "2020-02-19 09:18:37";
    SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
    Date date = simpleDateFormat.parse(str);
}

时间戳和Date互转

@Test
public void timestamp2Date(){
	// 获取时间戳方式
    long timestamp1 = System.currentTimeMillis();
    long timestamp2 = new Date().getTime();

	// 构造函数传入时间戳
    Date date = new Date(timestamp1);

    System.out.println(timestamp1);
    System.out.println(timestamp2);
    System.out.println(date);
}

@Test
public void date2Timestamp(){
    Date date = new Date();
    // 获取当前时间的时间戳
    long timestamp = date.getTime();
}

时间相加减，通过getTime()获取时间戳进行

@Test
public void dateAddAndSub() throws Exception{
    String str1 = "2020-02-11 01:02:03";
    String str2 = "2020-02-12 10:20:40";
    String str3 = "2020-02-19 09:25:01";

    SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
    Date date1 = dateFormat.parse(str1);
    Date date2 = dateFormat.parse(str2);
    Date date3 = dateFormat.parse(str3);

    long timestamp = date3.getTime() + ( date2.getTime() - date1.getTime());
    String str4 = dateFormat.format(new Date(timestamp));

}

参考：
Java 日期时间