Three ways to generate different random numbers in java

There are three main ways to generate random numbers in java:

1, new Random()

2, Math.random()

3, currentTimeMillis()

The first type requires the help of the java.util.Random class to generate a random number. Constructor, which is also the most commonly used one, has two constructors, Random() and Random(long seed). The first one uses the current time as the default seed, and the second one uses the specified seed value. After generation, different types of numbers are generated with the help of different statements.

(Related video tutorial sharing: java video tutorial)

The seed is the first use value of the random number generated. The mechanism is to use a function to convert the seed The value is converted into a certain point in the random number space, and the generated random numbers are evenly distributed in the space. The random numbers generated in the future are related to the previous random number.

For example:

public static void main(String[] args)
{    
　　Random r = new Random(1);
　　for(int i=0 ; i<5 ;  i++)
　　{
　　　　int ran1 = r.nextInt(100);
　　　　System.out.println(ran1);
　　}
}

The five numbers generated by my compiler are all 85,88,47,13,54. If Random r = new Random() is used, the Random numbers are different, and this is the result of determining the seed.

The value returned by the second method is a double value of [0.0, 1.0). Since the precision of the double class number is very high, it can be regarded as a random number to a certain extent, and the type is determined with the help of (int) After conversion, you can get an integer random number.

For example:

public static void main(String[] args)2     {    
int max=100,min=1;
 int ran2 = (int) (Math.random()*(max-min)+min); 
System.out.println(ran2);6     }

Although the third method is not commonly used, it is also an idea. The method returns a long number of milliseconds from 0:00:00 on January 1, 1970 (this is related to the UNIX system) to the present. After taking the modulo, a random number within the required range can be obtained.

For example:

public static void main(String[] args)
    {    
        int max=100,min=1;
        long randomNum = System.currentTimeMillis();  
        int ran3 = (int) (randomNum%(max-min)+min);  
        System.out.println(ran3);
        
    }

Related article tutorial sharing: java introductory tutorial

The above is the detailed content of Three ways to generate different random numbers in java. For more information, please follow other related articles on the PHP Chinese website!