Lesson 3.4 -
Random Integers
Purpose: To learn how to declare and use a random integer generator
If you can't beat 'em, random! The use of randomness has numerous applications from video games to computerized simulations. In Java, there are a few ways to generate random integers. We will use the random method from Java's Math class.
The Math class random method is used as follows :
double x = Math.random(); //random decimal from 0-1
OR Generate a random number and display it without storing the value:
System.out.println( Math.random() );
To generate a random integer from 0 to n-1:
int y = (int) (n * Math.random());
OR more usefully, we generate a random integer from 1 to n:
int y = (int) (n * Math.random()) + 1;
In general, to generate a random integer between a and b:
int y = (int) ((b-a+1) * Math.random()) + a;
In closing, The Math class random method generates decimal values. To get the necessary integer for a program, use the appropriate formula as follows:
1. 0 to n-1 : (int) (n * Math.random())
2. 1 to n : (int) (n * Math.random()) + 1
3. a to b : (int) ((b-a+1) * Math.random()) + a
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