Prime Number Program in Java

Prime Number Program in Java:
The prime number is a natural number who value is greater than 1 and can be divisible by 1 and by itself.
The number of counts to find the prime numbers is 2 because it can divisible only by 1 and by itself
For example:
6 - can be divisible by 1x6,2x3,3x2,6x1. where the count is 4 and it is not a prime number
7 - can be divisible by 1x7,7x1. where the count is 2 and it is a prime number

Example 1:
Program to check whether the given number is prime number or not

import java.util.Scanner;
public class Primenumbers
{
public static void main(String[] args)
{
int i =2;
boolean flag = true;
System.out.print("Enter the number to find it is prime or not: ");
Scanner sc = new Scanner(System.in);
int n = sc.nextInt();
if(n<0)
{
System.out.println("The prime number cannot be negative");
}
else
{
while(i<n)
{
if(n%i==0)
{
flag = false;
break;
}
i++;
}
if(flag)
{
System.out.println(n + " is a prime number");
}
else
{
System.out.println(n + " is not a prime number");
}
}
}
}
Output:
Enter the number to find it is prime or not: 191
191 is a prime number

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Example 2:
Program to display first n prime numbers

import java.util.Scanner;
public class Primenumbers
{
public static void main(String[] args)
{
int num=0,i=0;
int counter;
System.out.print("Enter the range of prime numbers: ");
Scanner sc = new Scanner(System.in);
int n = sc.nextInt();
if(n<0)
{
System.out.println("Prime numbers cannot be negative");
}
else
{
for(i=1;i<=n;i++)
{
counter = 0;
for(num=1;num<=i;num++)
{
if(i%num==0)
{
counter = counter + 1;
}
}
if(counter==2)
{
System.out.print(i + ",");
}
}
}
}
}
Output:
Enter the range of prime numbers: 200
2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97,101,103,1
07,109,113,127,131,137,139,149,151,157,163,167,173,179,181,191,193,197,199,

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Example 3:
Program to find the prime numbers between two numbers

import java.util.Scanner;
public class Primenumbers
{
public static void main(String[] args)
{
int counter;
System.out.print("Enter the starting number: ");
Scanner s = new Scanner(System.in);
int start = s.nextInt();
System.out.print("Enter the ending number: ");
Scanner e = new Scanner(System.in);
int end = e.nextInt();

if(start<0 || end<0)
{
System.out.println("The prime numbers cannot be negative");
}
else
{
for(int i = start; i<=end;i++)
{
counter = 0;
for(int num = 1; num<=i;num++)
{
if(i%num == 0)
{
counter = counter+1;
}
}
if(counter == 2)
{
System.out.print(i + ",");
}
}
}

}
}
Output:
Enter the starting number: 12
Enter the ending number: 80
13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,

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