Come generare numeri casuali in Java con alcune variazioni?

Pubblicato: 2019-02-27
numero casuale crunchify

In Java, esiste un metodo random() nella classe Math , che restituisce un valore doppio compreso tra 0.0 and 1.0 . Nella classe Random esiste un metodo nextInt(int n) , che restituisce un valore casuale compreso tra 0 (incluso) e n (esclusivo).

Sono sicuro che devi aver affrontato le seguenti domande in passato:

  • Come generare numeri casuali in Java?
  • Generazione di numeri casuali in un intervallo con Java
  • Dove posso trovare esempi di numeri casuali Java?
  • Esempio di metodo Java.lang.Math.random()

Ecco un semplice esempio che utilizza la funzione Random() e fornisce risposta a tutte le tue domande.

Come generare numeri casuali in Java con alcune variazioni?

Questo è quello che stiamo facendo qui:

  • Crea il metodo RandomTest1 () che è un semplice test che stampa un numero casuale compreso tra il numero minimo e quello massimo (Esempio di intervallo di numeri).
  • Crea il metodo RandomTest2 () che è un semplice test che stampa una voce casuale dall'elenco.
  • Crea Two Threads in main ed run il metodo Main.
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package crunchify . com . tutorials ;
 
import java . util . ArrayList ;
import java . util . List ;
import java . util . Random ;
 
/**
* @author Crunchify.com
* How to Generate Random Number in Java with Some Variations?
*/
 
public class CrunchifyRandomNumber {
 
     // Simple test which prints random number between min and max number (Number Range Example)
     public void RandomTest1 ( ) throws InterruptedException {
         while ( true ) {
             int min = 50 ;
             int max = 100 ;
 
             // random() returns a double value with a positive sign, greater than or equal to 0.0 and less than 1.0.
// Returned values are chosen pseudorandomly with (approximately) uniform distribution from that range.
             float randomNumber = ( min + ( float ) ( Math . random ( ) * ( ( max - min ) ) ) ) ;
             System . out . println ( "Crunchify Thread 1 random result: " + randomNumber ) ;
 
             // sleep() causes the currently executing thread to sleep (temporarily cease execution) for the specified number of milliseconds,
             // subject to the precision and accuracy of system timers and schedulers.
             // The thread does not lose ownership of any monitors.
             Thread . sleep ( 500 ) ;
         }
     }
 
     // Simple test which prints random entry from list below
     public void RandomTest2 ( ) throws InterruptedException {
         List < String > list = new ArrayList < String > ( ) ;
         list . add ( "Facebook" ) ;
         list . add ( "Twitter" ) ;
         list . add ( "Google" ) ;
 
         Random randomNumber = new Random ( ) ;
         String randomEle ;
         int listSize = list . size ( ) ;
 
         while ( true ) {
             randomEle = list . get ( randomNumber . nextInt ( listSize ) ) ;
             System . out . println ( "Crunchify Thread 2 random result: " + randomEle ) ;
             Thread . sleep ( 500 ) ;
         }
     }
 
     static public void main ( String [ ] args ) {
 
         // Let's run both Test1 and Test2 methods in parallel..
         Thread crunchifyThread1 = new Thread ( ) {
             public void run ( ) {
                 CrunchifyRandomNumber crNumber = new CrunchifyRandomNumber ( ) ;
                 try {
                     crNumber . RandomTest1 ( ) ;
                 } catch ( InterruptedException e ) {
                     e . printStackTrace ( ) ;
                 }
             }
         } ;
         Thread crunchifyThread2 = new Thread ( ) {
             public void run ( ) {
                 CrunchifyRandomNumber crNumber = new CrunchifyRandomNumber ( ) ;
                 try {
                     crNumber . RandomTest2 ( ) ;
                 } catch ( InterruptedException e ) {
                     e . printStackTrace ( ) ;
                 }
             }
         } ;
 
         // start() Causes this thread to begin execution; the Java Virtual Machine calls the run method of this thread.
//The result is that two threads are running concurrently: the current thread
// (which returns from the call to the start method) and the other thread (which executes its run method).
         crunchifyThread1 . start ( ) ;
         crunchifyThread2 . start ( ) ;
     }
 
}
 

Uscita console Eclipse:

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/ Library / Java / JavaVirtualMachines / jdk - 15.jdk / Contents / Home / bin / java - javaagent : / Applications / IntelliJ IDEA . app / Contents / lib / idea_rt . jar = 55975 : / Applications / IntelliJ IDEA . app / Contents / bin - Dfile . encoding = UTF - 8 - classpath / Users / app / crunchify / github / CrunchifyTutorials / target / classes : / Users / app / crunchify / github / CrunchifyTutorials / WebContent / WEB - INF / lib / zxing - 2.1.jar : / Users / app / crunchify / github / CrunchifyTutorials / WebContent / WEB - INF / lib / commons - logging - 1.1.2.jar : / Users / app / crunchify / github / CrunchifyTutorials / WebContent / WEB - INF / lib / commons - collections - 3.2.1.jar : / Users / app / crunchify / github / CrunchifyTutorials / WebContent / WEB - INF / lib / javax . mail . jar : / Users / app / crunchify / github / CrunchifyTutorials / WebContent / WEB - INF / lib / commons - io - 2.4.jar : / Users / app / crunchify / github / CrunchifyTutorials / WebContent / WEB - INF / lib / commons - lang - 2.6.jar : / Users / app / crunchify / github / CrunchifyTutorials / WebContent / WEB - INF / lib / commons - configuration - 1.9.jar : / Users / app / crunchify / github / CrunchifyTutorials / WebContent / WEB - INF / lib / log4j - 1.2.17.jar : / Users / app / crunchify / github / CrunchifyTutorials / WebContent / WEB - INF / lib / commons - beanutils - 1.8.3.jar : / Users / app / . m2 / repository / org / glassfish / javax . json / 1.0.4 / javax . json - 1.0.4.jar : / Users / app / . m2 / repository / com / github / wnameless / json - flattener / 0.2.2 / json - flattener - 0.2.2.jar : / Users / app / . m2 / repository / com / eclipsesource / minimal - json / minimal - json / 0.9.4 / minimal - json - 0.9.4.jar : / Users / app / . m2 / repository / org / apache / commons / commons - lang3 / 3.10 / commons - lang3 - 3.10.jar : / Users / app / . m2 / repository / com / google / code / gson / gson / 2.8.0 / gson - 2.8.0.jar : / Users / app / . m2 / repository / net / jodah / expiringmap / 0.5.7 / expiringmap - 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jaxrpc / 1.4 / axis - jaxrpc - 1.4.jar : / Users / app / . m2 / repository / axis / axis - wsdl4j / 1.5.1 / axis - wsdl4j - 1.5.1.jar : / Users / app / . m2 / repository / commons - beanutils / commons - beanutils / 1.8.3 / commons - beanutils - 1.8.3.jar : / Users / app / . m2 / repository / commons - collections / commons - collections / 3.2.1 / commons - collections - 3.2.1.jar : / Users / app / . m2 / repository / commons - configuration / commons - configuration / 1.10 / commons - configuration - 1.10.jar : / Users / app / . m2 / repository / commons - io / commons - io / 2.4 / commons - io - 2.4.jar : / Users / app / . m2 / repository / commons - discovery / commons - discovery / 0.5 / commons - discovery - 0.5.jar : / Users / app / . m2 / repository / commons - lang / commons - lang / 2.6 / commons - lang - 2.6.jar : / Users / app / . m2 / repository / commons - logging / commons - logging / 1.1.3 / commons - logging - 1.1.3.jar : / Users / app / . m2 / repository / commons - logging / commons - logging - api / 1.1 / commons - logging - api - 1.1.jar : / Users / app / . m2 / repository / javax / mail / mail / 1.4.7 / mail - 1.4.7.jar : / Users / app / . m2 / repository / javax / activation / activation / 1.1 / activation - 1.1.jar : / Users / app / . m2 / repository / javax / xml / jaxrpc - api / 1.1 / jaxrpc - api - 1.1.jar : / Users / app / . m2 / repository / javax / servlet / javax . servlet - api / 3.1.0 / javax . servlet - api - 3.1.0.jar : / Users / app / . m2 / repository / org / apache / axis / axis - saaj / 1.4 / axis - saaj - 1.4.jar : / Users / app / . m2 / repository / wsdl4j / wsdl4j / 1.6.3 / wsdl4j - 1.6.3.jar : / Users / app / . m2 / repository / com / google / zxing / core / 3.2.1 / core - 3.2.1.jar : / Users / app / . m2 / repository / org / apache / commons / commons - compress / 1.9 / commons - compress - 1.9.jar : / Users / app / . m2 / repository / mysql / mysql - connector - java / 5.1.6 / mysql - connector - java - 5.1.6.jar : / Users / app / . m2 / repository / junit / junit / 4.12 / junit - 4.12.jar : / Users / app / . m2 / repository / org / hamcrest / hamcrest - core / 1.3 / hamcrest - core - 1.3.jar : / Users / app / . m2 / repository / ch / qos / logback / logback - classic / 1.2.3 / logback - classic - 1.2.3.jar : / Users / app / . m2 / repository / ch / qos / logback / logback - core / 1.2.3 / logback - core - 1.2.3.jar : / Users / app / . m2 / repository / org / springframework / spring - context / 5.1.3.RELEASE / spring - context - 5.1.3.RELEASE.jar : / Users / app / . m2 / repository / org / springframework / spring - aop / 5.1.3.RELEASE / spring - aop - 5.1.3.RELEASE.jar : / Users / app / . m2 / repository / org / springframework / spring - beans / 5.1.3.RELEASE / spring - beans - 5.1.3.RELEASE.jar : / Users / app / . m2 / repository / org / springframework / spring - core / 5.1.3.RELEASE / spring - core - 5.1.3.RELEASE.jar : / Users / app / . m2 / repository / org / springframework / spring - jcl / 5.1.3.RELEASE / spring - jcl - 5.1.3.RELEASE.jar : / Users / app / . m2 / repository / org / springframework / spring - expression / 5.1.3.RELEASE / spring - expression - 5.1.3.RELEASE.jar : / Users / app / . m2 / repository / org / springframework / spring - context - support / 5.1.3.RELEASE / spring - context - support - 5.1.3.RELEASE.jar crunchify . com . tutorials . CrunchifyRandomNumber
Crunchify Thread 2 random result : Twitter
Crunchify Thread 1 random result : 98.03486
Crunchify Thread 2 random result : Google
Crunchify Thread 1 random result : 57.48709
Crunchify Thread 2 random result : Google
Crunchify Thread 1 random result : 87.54976
Crunchify Thread 2 random result : Google
Crunchify Thread 1 random result : 75.2223
Crunchify Thread 2 random result : Facebook
Crunchify Thread 1 random result : 91.617584
Crunchify Thread 2 random result : Facebook
Crunchify Thread 1 random result : 64.705574
Crunchify Thread 2 random result : Google
Crunchify Thread 1 random result : 72.043884
Crunchify Thread 2 random result : Google
Crunchify Thread 1 random result : 70.38615
Crunchify Thread 2 random result : Facebook
Crunchify Thread 1 random result : 55.705227
Crunchify Thread 2 random result : Facebook
Crunchify Thread 1 random result : 76.36104
Crunchify Thread 2 random result : Twitter
Crunchify Thread 1 random result : 75.84907
 
Process finished with exit code 130 ( interrupted by signal 2 : SIGINT )
 

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