java util Random Class - java.util.Random Class in Java

java.util.Random Class

Random Class in Java

Java Random Class

The Java Random class is used to generate a stream of pseudorandom numbers. In other words Random class is used to generate random numbers in Java. The Java Random class uses a 48-bit seed, which is modified using a linear congruential formula.

If two instances of Random are created with the same seed, and the same sequence of method calls is made for each, they will generate and return identical sequences of numbers. In order to guarantee this property, particular algorithms are specified for the class Random. Java implementations must use all the algorithms shown here for the class Random, for the sake of absolute portability of Java code. However, subclasses of class Random are permitted to use other algorithms, so long as they adhere to the general contracts for all the methods.

• Instances of java.util.Random are threadsafe. However, the concurrent use of the same java.util.Random instance across threads may encounter contention and consequent poor performance. Consider instead using ThreadLocalRandom in multithreaded designs.
• Instances of java.util.Random are not cryptographically secure. Consider instead using SecureRandom to get a cryptographically secure pseudo-random number generator for use by security-sensitive applications.

java.util.Random Class Example

/*	Java Random Class Example
	Save with file name RandomExample.java	*/
public class RandomExample
{
	public static void main(String args[])
	{
		// java.util.Random DECLARATION
		java.util.Random r;
		// java.util.Random OBJECT CREATION
		// USING DEFAULT CONSTRUCTOR
		r = new java.util.Random();
		// java.util.Random OUTPUT
		// RETURNS NEXT RANDOM BOOLEAN
		System.out.println(r.nextBoolean());
		// RETURNS NEXT RANDOM INT
		System.out.println(r.nextInt());
		// RETURNS NEXT RANDOM INT
		System.out.println(r.nextInt(10));
		// RETURNS NEXT RANDOM FLOAT
		System.out.println(r.nextFloat());
		// RETURNS NEXT RANDOM LONG
		System.out.println(r.nextLong());
		// RETURNS NEXT RANDOM DOUBLE
		System.out.println(r.nextDouble());
		// SET THE SEED
		r.setSeed(10);
		// RETURNS NEXT RANDOM DOUBLE
		System.out.println(r.nextDouble());
	}
}

java.util.Random Class Example 2

/*	Java Random Class Example 2
	Save with file name RandomExample2.java	*/
public class RandomExample2
{
	public static void main(String args[])
	{
		// java.util.Random DECLARATION
		java.util.Random r;
		// java.util.Random OBJECT CREATION
		// USING PARAMETER CONSTRUCTOR
		r = new java.util.Random(100L);
		// java.util.Random OUTPUT
		// RETURNS NEXT RANDOM BOOLEAN
		System.out.println(r.nextBoolean());
		// RETURNS NEXT RANDOM INT
		System.out.println(r.nextInt());
		// RETURNS NEXT RANDOM INT
		System.out.println(r.nextInt(10));
		// RETURNS NEXT RANDOM FLOAT
		System.out.println(r.nextFloat());
		// RETURNS NEXT RANDOM LONG
		System.out.println(r.nextLong());
		// RETURNS NEXT RANDOM DOUBLE
		System.out.println(r.nextDouble());
	}
}