Links to the original text: https://blog.csdn.net/WuLex

Or because filling in self-built data tables requires a range of random dates, with the goal of being elegant, concise and efficient.
There are two ideas:

1. Generate a required 13-bit random number as milliseconds and convert milliseconds into Date classes in java.sql packages
2. A random year is generated, and then a random day is generated according to the range of days determined by the year and month.

First code, then efficiency comparison.
The designated scope is 2016-2018 (i.e. 1 January 2016-31 December 2018).
Method of generating thirteen random numbers:

	public static Date randomHireday() {
		int startYear=2016;									//Starting year of specified random date
		int endYear=2018;									//Starting year of specified random date (including)
		long start = Timestamp.valueOf(startYear+1+"-1-1 0:0:0").getTime();
		long end = Timestamp.valueOf(endYear+"-1-1 0:0:0").getTime();
		long ms=(long) ((end-start)*Math.random()+start);	//The qualified number of 13-bit milliseconds is obtained.
		Date hireday=new Date(ms);
		return hireday;
	}

Ten cycles:

Random years and days are generated respectively:

	public static Date randomHireday2() {
		int startYear=2016;
		int endYear=2018;
		int year = (int)(Math.random()*(endYear-startYear+1))+startYear;	//Random year
		int month= (int)(Math.random()*12)+1;								//Random Month
		Calendar c = Calendar.getInstance();				//Create Calendar objects
		c.set(year, month, 0);								//Setting Date
		int dayOfMonth = c.get(Calendar.DAY_OF_MONTH);		//How many days to get the corresponding year and month
		int day=(int)(Math.random()*dayOfMonth+1)	;		//Generating random days
		Date hireday=Date.valueOf(year+"-"+month+"-"+day);	//Generating Date Object by valueOf Method
		return hireday;
	}

Ten cycles:

Now start testing efficiency, 10 short tests and 100,000 long tests, respectively.

	public static void main(String[] args) {
		//Random thirteen digits
		long start;
		long end;
		start = System.currentTimeMillis();
		for(int i=0;i<10;i++) {
			randomHireday();
		}
		end = System.currentTimeMillis();
		System.out.println("Time spent in 10 cycles of random 13 digits:"+(end-start));
		
		start = System.currentTimeMillis();
		for(int i=0;i<100000;i++) {
			randomHireday();
		}
		end = System.currentTimeMillis();
		System.out.println("Time spent in 100,000 random 13-digit cycles:"+(end-start));
		
		//Random generation year, month and day
		start = System.currentTimeMillis();
		for(int i=0;i<10;i++) {
			randomHireday2();
		}
		end = System.currentTimeMillis();
		System.out.println("Time spent in 10 cycles of each random generation year, month and day:"+(end-start));
		
		start = System.currentTimeMillis();
		for(int i=0;i<100000;i++) {
			randomHireday2();
		}
		end = System.currentTimeMillis();
		System.out.println("Time spent in 100,000 cycles of random generation year, month and day:"+(end-start));
	}

Obviously, the more concise and elegant method of thirteen random numbers is more efficient.
Thus, we can get an elegant, concise and efficient random date generation method.