Comp102 lec 5.0
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This document discusses two methods for generating random numbers in Java: using the Random class and using the Math class. The Random class allows generation of random integers within a specified range using the nextInt() method. The Math class random() method returns a double value between 0 and 1 that can be scaled to generate random integers. Both methods are useful for applications requiring random numbers.
![What if I have to generate a
Random Number from 0 –Random
Will generate a
50,
Will generate a
both inclusivethen0subtractfrom
Number from 0 – 99 first
random number
and -49 50
fromWill generate random
Will generate number
generated a a
A = rand.nextInt(50); thus numberthe range50
defines from 0 - as
random number from
[0 – 49 and then will
0 – 50] – [99 – 50] =
A = rand.nextInt(51); -50 - 49
add 1 to it, makes
range as 1 – 50
A = rand.nextInt(100)-50;
A = rand.nextInt(50)+1;](https://image.slidesharecdn.com/comp102-lec5-0-121104113746-phpapp02/85/Comp102-lec-5-0-7-320.jpg)
![Math.random() call
double x = Math.random();
Returns a double value with a positive
sign, greater than or equal to 0.0 and
less than 1.0.
Will assign a value to x from [0.0 –
0.999]](https://image.slidesharecdn.com/comp102-lec5-0-121104113746-phpapp02/85/Comp102-lec-5-0-11-320.jpg)
![Generate Integer Random
Number
Math.random()*10
[0.0 – 9.99]
Convert it into Integer by type casting
(int)(Math.random()*10)
[0 – 9]
Math.random()*100
[0.0 – 99.99]
Convert it into Integer by type casting
(int)(Math.random()*100
[0 – 99]](https://image.slidesharecdn.com/comp102-lec5-0-121104113746-phpapp02/85/Comp102-lec-5-0-12-320.jpg)
Comp102 lec 5.0
- 2. Two Methods By using Random Library Class By using Math Library Class
- 3. RANDOM CLASS
- 4. Random Class To use a class Import the class library import java.util.Random; OR import java.util.*; Create an object of class Random “name of object” = new Random() E.g • Random rand = new Random();
- 5. Generate a Random Number Integer Have/Declare an integer variable int a; Assign it a random value a=“object”.nextInt(“Value to define Range”); E.g a = rand.nextInt(100); If value is 100, range is 0 – 99 Value will define the range as starting from 0 to one less than the value
- 6. Define Ranges, where A is an Integer and rand is Random Object A= rand.nextInt(100) 0 - 99 A= rand.nextInt(10) 0-9 A= rand.nextInt(101) 0 - 100 A= rand.nextInt(99) 0 - 98 A= rand.nextInt(100) + 0 – 99 and then add 5 to it => 5 5-104 A= rand.nextInt(100) – 0 -99 and then subtract 10 => 10 -10 – 89 A= rand.nextInt(10) + 1 0 – 9 and then add 1 => 1 - 10 0-100 and then add 5 => 5 - 105 A= rand.nextInt(101)+5 0-9 and then subtract 10 => -10 – (- A= rand.nextInt(10) -10 1)
- 7. What if I have to generate a Random Number from 0 –Random Will generate a 50, Will generate a both inclusivethen0subtractfrom Number from 0 – 99 first random number and -49 50 fromWill generate random Will generate number generated a a A = rand.nextInt(50); thus numberthe range50 defines from 0 - as random number from [0 – 49 and then will 0 – 50] – [99 – 50] = A = rand.nextInt(51); -50 - 49 add 1 to it, makes range as 1 – 50 A = rand.nextInt(100)-50; A = rand.nextInt(50)+1;
- 8. What if I have to generate a Random Number from 5 – 15 both inclusive? a = rand.nextInt(15); a = rand.nextInt(16); a = rand.nextInt(10)+5; a = rand.nextInt(11)+5;
- 9. Random Real Numbers To generate a random real number uniformly distributed between 0 and 1, use the "nextDouble" message. This message takes no parameters. For example... double r = rand.nextDouble();
- 10. CLASS MATH
- 11. Math.random() call double x = Math.random(); Returns a double value with a positive sign, greater than or equal to 0.0 and less than 1.0. Will assign a value to x from [0.0 – 0.999]
- 12. Generate Integer Random Number Math.random()*10 [0.0 – 9.99] Convert it into Integer by type casting (int)(Math.random()*10) [0 – 9] Math.random()*100 [0.0 – 99.99] Convert it into Integer by type casting (int)(Math.random()*100 [0 – 99]