In Java, there is a method random() in the Math class, which returns a double value between 0.0 and 1.0. In the class Random there is a method nextInt(int n) , which returns a random value in the range of 0 (inclusive) and n (exclusive).
I’m sure you must have faced below questions in past:
- How to generate random numbers in Java?
- Generating random number in a range with Java
- Where can I find Java Random Numbers Examples?
- Java.lang.Math.random() Method Example
Here is a simple example which uses Random() function and provides answer to all of your questions.
This is what we are doing here:
- Create method
RandomTest1() which is a simple test which prints random number between min and max number (Number Range Example). - Create method
RandomTest2() which is a simple test which prints random entry from the list. - Create
Two Threadsin main andrunMain method.
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 Console Output:
/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 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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