A detailed introduction to date operations in Java

Introduces how to obtain Java dates and Java date operations.

1. Get the current date:

java.util.Date date = new java.util.Date();

This is the Date under the util package, not sql Under the package, do not quote errors.

This date cannot be output directly. It is in line with our aesthetics to format it and then output it.

Formatting method:

java.text.SimpleDateFormat formatter = new java.text.SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

The format in brackets is defined by yourself, and it can also be other formats such as: "yyyy year MM month dd day", "yyyy/MM/dd" can Define it according to your actual situation.

2. Use Calendar to get the current date:

Calendar cal = Calendar.getInstance();
System.out.println("Current Date: " + cal.getTime());

The output result is:

Current Date: Tue Jun 10 10:31:44 CST 2014

3. Use TimeStamp to get the current date:

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
Timestamp now = new Timestamp(System.currentTimeMillis()); 
String sf = sdf.format(now);
System.out.println(sf);

Output result:

2014-06-10

4. Current day:

 int day = cal.get(Calendar.DATE);

Current month: (Note: the month starts from 0) int month = cal.get(Calendar.MONTH) + 1;

Current year: int year = cal.get(Calendar.YEAR);

Day of the week: (Sunday is the first day of the week abroad) int dow = cal.get(Calendar. DAY_OF_WEEK);

The day of this month: int dom = cal.get(Calendar.DAY_OF_MONTH);

The day of this year: int doy = cal.get(Calendar. DAY_OF_YEAR);

 System.out.println("Day: " + day);输出结果：Day：10
  System.out.println("Month: " + month);输出结果：Month：6
  System.out.println("Year: " + year);输出结果：Year：2014
  System.out.println("Day of Week: " + dow);输出结果：Day of Week:3(今天星期二)
  System.out.println("Day of Month: " + dom);输出结果：Day of Month：10
  System.out.println("Day of Year: " + doy);输出结果：Day of Year:161

5. Convert a string in the specified format to a date:

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
Date sd = sdf.parse("2013-12-25");

Java Date Operation

1. The difference between two dates:

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
Date d1=sdf.parse("2013-12-25");
Date d2=sdf.parse("2013-12-29");
long result =(d2.getTime()-d1.getTime())/(24*60*60*1000);
System.out.println(result);

Output result: 4

2. Add the number of days to the specified date:

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
Date sd = sdf.parse("2013-12-23");
Calendar cal1 = new GregorianCalendar();
cal1.setTime(sd);
cal1.add(Calendar.DATE, 161);
System.out.println(sdf.format(cal1.getTime()));

3.

Calendar cal = Calendar.getInstance();

Add a few days to the current date:

cal.add(Calendar.DATE, 161);

Subtract a few days from the current date:

cal.add(Calendar.DATE, -161);

Add months to the current date:

cal.add(Calendar.MONTH,2);
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void java.util.Calendar.add(int field, int amount)

Just change the field.

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