The Random Class The Random class is part of the java.util package

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Presentation transcript:

The Random Class The Random class is part of the java.util package It provides methods that generate pseudorandom numbers A Random object performs complicated calculations based on a seed value to produce a stream of seemingly random values See RandomNumbers.java Copyright © 2017 Pearson Education, Inc.

//******************************************************************** // RandomNumbers.java Author: Lewis/Loftus // // Demonstrates the creation of pseudo-random numbers using the // Random class. import java.util.Random; public class RandomNumbers { //----------------------------------------------------------------- // Generates random numbers in various ranges. public static void main(String[] args) Random generator = new Random(); int num1; float num2; num1 = generator.nextInt(); System.out.println("A random integer: " + num1); num1 = generator.nextInt(10); System.out.println("From 0 to 9: " + num1); continued Copyright © 2017 Pearson Education, Inc.

num1 = generator.nextInt(10) + 1; continued num1 = generator.nextInt(10) + 1; System.out.println("From 1 to 10: " + num1); num1 = generator.nextInt(15) + 20; System.out.println("From 20 to 34: " + num1); num1 = generator.nextInt(20) - 10; System.out.println("From -10 to 9: " + num1); num2 = generator.nextFloat(); System.out.println("A random float (between 0-1): " + num2); num2 = generator.nextFloat() * 6; // 0.0 to 5.999999 num1 = (int)num2 + 1; System.out.println("From 1 to 6: " + num1); } Copyright © 2017 Pearson Education, Inc.

Sample Run A random integer: 672981683 From 0 to 9: 0 From 1 to 10: 3 A random float (between 0-1): 0.18538326 From 1 to 6: 3 continued num1 = generator.nextInt(10) + 1; System.out.println ("From 1 to 10: " + num1); num1 = generator.nextInt(15) + 20; System.out.println ("From 20 to 34: " + num1); num1 = generator.nextInt(20) - 10; System.out.println ("From -10 to 9: " + num1); num2 = generator.nextFloat(); System.out.println("A random float (between 0-1): " + num2); num2 = generator.nextFloat() * 6; // 0.0 to 5.999999 num1 = (int)num2 + 1; System.out.println("From 1 to 6: " + num1); } Copyright © 2017 Pearson Education, Inc.

Quick Check Given a Random object named gen, what range of values are produced by the following expressions? gen.nextInt(25) gen.nextInt(6) + 1 gen.nextInt(100) + 10 gen.nextInt(50) + 100 gen.nextInt(10) – 5 gen.nextInt(22) + 12 Copyright © 2017 Pearson Education, Inc.

Quick Check Given a Random object named gen, what range of values are produced by the following expressions? Range 0 to 24 1 to 6 10 to 109 100 to 149 -5 to 4 12 to 33 gen.nextInt(25) gen.nextInt(6) + 1 gen.nextInt(100) + 10 gen.nextInt(50) + 100 gen.nextInt(10) – 5 gen.nextInt(22) + 12 Copyright © 2017 Pearson Education, Inc.

Quick Check Write an expression that produces a random integer in the following ranges: Range 0 to 12 1 to 20 15 to 20 -10 to 0 Copyright © 2017 Pearson Education, Inc.

Quick Check Write an expression that produces a random integer in the following ranges: Range 0 to 12 1 to 20 15 to 20 -10 to 0 gen.nextInt(13) gen.nextInt(20) + 1 gen.nextInt(6) + 15 gen.nextInt(11) – 10 Copyright © 2017 Pearson Education, Inc.