Java Generate Random Number Program

---

What is Random Number?

A Random Number is any number generated by a computer. Ex - Just like we call the person by any random number as ID.

Need and Examples of Random Numbers

• For generating any random passwords
• Asking questions based on random sequence
• For showing word of the day in Dictionary app
• For generating random phone numbers
• Banking token system

---

Program Example 1 : Generate Any Random Number

Java provides built in Class called java.util.Random for generating the random numbers. We can generate Random Integer number by calling nextInt() method

import java.util.Random;

public class RandomGen 
{
	public static void main(String[] args) 
	{
		Random ran = new Random();
		int num = ran.nextInt();
        
            //or call directly as 
		// int num = new Random().nextInt();
        
		System.out.println("Random number is "+num);
	}
}

Output

We can also generate following types using Random class

• Boolean value using nextBoolean()
• Float value using nextFloat()
• Double value using nextDouble()
• Long value using nextLong()

---

Program Example 2 : Generate Random Number Within Range

import java.util.Random;
public class RandomRangeEx 
{
	static int Generate(int max,int min)
	{
		Random ran = new Random();
		return ran.nextInt((max-min)+1)+min;
	}
	public static void main(String[] args) 
	{
		int min, max;
		min = 1;
		max = 5;
		int randomValue = Generate(max, min);
		System.out.println("Random number between "+min+" to "+max+" = "+randomValue);
	}
}

Output

---

Program Example 3 : Generate Any Random Alphabet

import java.util.Random;
public class RandomCharGenEx 
{
	static int value;
	static int Generate(int max,int min)
	{
		Random ran = new Random();
		value = ran.nextInt((max-min)+1)+min;
		return value;
	}
	public static void main(String[] args) 
	{
		int Capitalmin = 65; //ascii value of capital A
		int Capitalmax = 90; // ascii value of small Z
		char Alphabet;
		int randomValue = Generate(Capitalmax, Capitalmin);
		System.out.println("Random number is "+randomValue);
	
		Alphabet = (char) randomValue;
		System.out.println("Char = "+Alphabet);
	}
}

Output

---

Program Example 4 : Generate Non Repeated Set of Random Numbers

import java.util.*;
public class RandomNumArrayEx 
{
	int value;
	Random ran = new Random();
	static Vector v = new Vector();
	void GenerateNubs(int totalElements)
	{
		value = ran.nextInt((5-1)+1)+1;
		v.add(value); // initially add any one value
		while(v.size()<totalElements) // repeat till we get totalElements
		{
			if(v.contains(value)) // to avoid repeat values
				value = ran.nextInt((5-1)+1)+1;
			else // if not repeated then add to vector
				v.add(value);
		}
	}
	
	public static void main(String[] args) 
	{
		int totalElements = 5;
		RandomNumArrayEx ra = new RandomNumArrayEx();
		ra.GenerateNubs(totalElements);
		
		System.out.println("Set = "+RandomNumArrayEx.v);
	}
}

Output