[Windows10][jdk15] 객체 지향 프로그래밍(OOP) Java 실습 03 - Random 활용하기

 

 [ 작업 환경 ]

 

Windows10

jdk-15

 

 

 

 

 

1. RandomNumbers.java 소스 작성

 

//********************************************************************
//  RandomNumbers.java       Java Foundations
//
//  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);

      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);
   }
}

 

 

 

 

 

2. 프로그램 실행 예시

 

javac RandomNumbers.java

java RandomNumbers.java

 

 

 

 

 

3. 연습해보기

 

// 문제

아래와 같이 int 타입의 변수 a와 b를 선언했다고 하자.
int a = 10; 
int b = 20;

Random number r을 a <= r <= b 범위를 만족하도록 생성하는 java 프로그램을 작성하시오.

 

//********************************************************************
//  RandomNumbers.java       Java Foundations
//
//  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 = 10;
      float num2 = 20;
      float r;
      // 0 ~ 1 랜덤 변수 출력
      r = generator.nextFloat();
      System.out.println ("A random integer: " + r);
      // 10 ~ 20 랜덤 정수 출력
      r = generator.nextInt(11) + 10;
      System.out.println ("From 10 to 20: " + (int)r);
      // 10~20 랜덤 실수 출력
      r = generator.nextFloat() * 10 + 10;
      System.out.println ("From 10.00000 to 20.00000: " + r);
      
   }
}

 

 

 

 

 

4. 연습해보기 실행 예시

 

javac RandomNumbers.java

java RandomNumbers.java