Prime Number: A number that
is divisible only by itself and 1 is called Prime number.
Examples: 2, 3, 5, 7, 11,
13, 17, 19 etc.
Prime number programs in Java:
Program to display the prime numbers from 1 to
100
public class Prime
{
public static void main(String[] args)
{
int
limit = 100;
System.out.println("Prime numbers between 1 and 100");
for(int i=2; i < limit; i++)
{
boolean isPrime = true;
for(int j=2; j < i ; j++)
{
if(i % j == 0)
{
isPrime = false;
break;
}
}
if(isPrime)
System.out.print(i + " ");
}
}
}
|
Output:
Prime numbers between 1 and 100
1 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
|
Program to display prime numbers from 1 to n:
import java.util.Scanner;
public class Prime2
{
public static void main(String[] args)
{
Scanner s1 = new Scanner(System.in);
System.out.println("Enter the value of
N");
int
n = s1.nextInt();
for(int i=2; i < n; i++)
{
boolean isPrime = true;
for(int j=2; j < i ; j++)
{
if(i % j == 0)
{
isPrime = false;
break;
}
}
if(isPrime)
System.out.print(i + " ");
}
}
}
|
Output:
Enter the value of N
40
2 3 5 7 11 13 17 19 23 29 31 37
|
Prime Number Program using Method in Java:
class Prime3
{
void
ToCheckPrime(int n)
{
int
i,j=0,k=0;
j =
n/2;
if(n==0||n==1)
{
System.out.println(n+" is not prime number");
}
else
{
for(i = 2;i <= j;i++)
{
if(n%i == 0)
{
System.out.println(n+" is not prime number");
k = 1;
break;
}
}
if(k == 0)
{
System.out.println(n+" is prime number");
}
}
}
public static void main(String[] args)
{
Prime3 p1 = new Prime3();
p1.ToCheckPrime(1);
p1.ToCheckPrime(5);
p1.ToCheckPrime(8);
}
}
|
Output:
1 is not prime number
5 is prime number
8 is not prime number
|
Program to Check Prime Number using a while loop:
import java.util.Scanner;
class Prime4
{
public static void main(String[] args)
{
Scanner s1 = new Scanner(System.in);
System.out.println("Enter the value of
N");
int
n = s1.nextInt();
int
i = 2;
boolean flag = false;
while(i <= n/2)
{
if(n % i == 0)
{
flag = true;
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 value of N
15
15 is not a prime number.
|
Find prime numbers between two numbers:
import java.util.Scanner;
public class Prime5
{
public static void main(String[] args)
{
Scanner s = new Scanner(System.in);
System.out.print("Enter the first number = ");
int firstNumber = s.nextInt();
System.out.print("Enter the second number = ");
int secondNumber = s.nextInt();
System.out.println(" The prime numbers between " + firstNumber
+ " and " + secondNumber);
for (int i = firstNumber; i <= secondNumber; i++)
{
if (isPrime(i))
{
System.out.println(i);
}
}
}
public static boolean isPrime(int n) {
if (n <= 1)
{
return false;
}
for (int i = 2; i <= Math.sqrt(n); i++)
{
if (n % i == 0)
{
return false;
}
}
return true;
}
}
|
Output:
Enter the first number = 2
Enter the second number = 15
The
prime numbers between 2 and 15
2
3
5
7
11
13
|
See also: Palindrome program in Java