いくつかのバリエーションがあるJavaで乱数を生成する方法は？

公開: 2019-02-27

Javaでは、 Mathクラスにrandom()メソッドがあり、 0.0 and 1.0までのdouble値を返します。クラスRandomには、メソッドnextInt(int n)があります。このメソッドは、0（包括的）からn（排他的）の範囲のランダムな値を返します。

私はあなたが過去に以下の質問に直面したに違いないと確信しています：

Javaで乱数を生成する方法は？
Javaで範囲内の乱数を生成する
Java乱数の例はどこにありますか？
Java.lang.Math.random（）メソッドの例

これは、Random（）関数を使用して、すべての質問に対する回答を提供する簡単な例です。

これが私たちがここで行っていることです：

最小数と最大数の間の乱数を出力する単純なテストであるメソッドRandomTest1 （）を作成します（数値範囲の例）。
リストからランダムなエントリを出力する単純なテストであるメソッドRandomTest2 （）を作成します。
mainにTwo Threadsを作成し、Mainメソッドをrunします。

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 ( ) ;

}

Eclipseコンソールの出力：

/ 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 - 0.5.7.jar : / Users / app / . m2 / repository / org / apache / httpcomponents / httpclient / 4.3.6 / httpclient - 4.3.6.jar : / Users / app / . m2 / repository / org / apache / httpcomponents / httpcore / 4.3.3 / httpcore - 4.3.3.jar : / Users / app / . m2 / repository / commons - codec / commons - codec / 1.6 / commons - codec - 1.6.jar : / Users / app / . m2 / repository / org / json / json / 20151123 / json - 20151123.jar : / Users / app / . m2 / repository / net / spy / spymemcached / 2.12.3 / spymemcached - 2.12.3.jar : / Users / app / . m2 / repository / com / whalin / Memcached - Java - Client / 3.0.2 / Memcached - Java - Client - 3.0.2.jar : / Users / app / . m2 / repository / commons - pool / commons - pool / 1.5.6 / commons - pool - 1.5.6.jar : / Users / app / . m2 / repository / org / slf4j / slf4j - api / 1.6.4 / slf4j - api - 1.6.4.jar : / Users / app / . m2 / repository / com / googlecode / xmemcached / xmemcached / 2.4.5 / xmemcached - 2.4.5.jar : / Users / app / . m2 / repository / com / paypal / sdk / rest - api - sdk / 1.14.0 / rest - api - sdk - 1.14.0.jar : / Users / app / . m2 / repository / commons - dbcp / commons - dbcp / 20030825.184428 / commons - dbcp - 20030825.184428.jar : / Users / app / . m2 / repository / javax / ws / rs / javax . ws . rs - api / 2.0 / javax . ws . rs - api - 2.0.jar : / Users / app / . m2 / repository / org / hamcrest / hamcrest - all / 1.3 / hamcrest - all - 1.3.jar : / Users / app / . m2 / repository / log4j / log4j / 1.2.17 / log4j - 1.2.17.jar : / Users / app / . m2 / repository / com / google / guava / guava / 19.0 / guava - 19.0.jar : / Users / app / . m2 / repository / com / googlecode / json - simple / json - simple / 1.1 / json - simple - 1.1.jar : / Users / app / . m2 / repository / commons - net / commons - net / 2.0 / commons - net - 2.0.jar : / Users / app / . m2 / repository / asm / asm / 3.3.1 / asm - 3.3.1.jar : / Users / app / . m2 / repository / axis / axis / 1.4 / axis - 1.4.jar : / Users / app / . m2 / repository / org / apache / axis / axis - 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