# Field Manual for Hackers

## write a program to test whether a given number is prime or not.? (Without Goto)

1. import java.util.Scanner;

class Test{

public static void main(String ar[])
{

Scanner sc=new Scanner(System.in);
double num,count=0;
System.out.println("Enter Number");
num=sc.nextDouble();

for(int i=1;i<=num;i++){
if(num%i==0)
count++;
}

if(count==2)
System.out.println("Prime Number");
else
System.out.println("Not a Prime Number");

}
}

2. import java.util.Scanner;

class Test
{

public static void main(String ar[])
{

int i=2,flag=0,number;
System.out.print("Enter number: ");
Scanner w=new Scanner(System.in);
number=w.nextInt();
while(i<number)
{
if(number%i==0)
flag=1;
i++;
}
if(flag!=1)
{
System.out.print(number+" is a prime number.");
}
else
System.out.print(number+" is not a prime number.");
}
}

3. public class prime
{
public static void main(String args[])
{
boolean test=false;
int n=Integer.parseInt(args[0]);
for(int i=2;i1)
{

System.out.print("\n entered number is prime");
}
else
{
System.out.print("\n entered number is not prime");
}
}
}

4. import java.util.Scanner;
class Prime
{
public static void main(String Args[])
{
Scanner sc=new Scanner(System.in);
System.out.println("enter the number");
int num=sc.nextInt();
int c=0;
for(int i=1;i<=num;i++)
{
if(num%i==0)
c++;
}
if(c==2)
System.out.println("it is a prime number");
else
System.out.println("it is not a prime number");
}
}

5. import java.util.Scanner;
public class prime {
public static void main(String args[])
{
Scanner scan = new Scanner(System.in);
double num;
System.out.println("enter the number");
num = scan.nextDouble();
boolean flag = false;
for(int i=2;i<=num/2;i++)
{
if(num%i==0)
{ flag = true;
break;
}
}
if(!flag)
System.out.println("the number is prime");
else
System.out.println("the number is not prime");
}
}

6. package forloop;
import java.util.*;
{
public static void main(String args[])
{
int i,n,count=0;
System.out.println("enter number");
Scanner sc=new Scanner(System.in);
n=sc.nextInt();
for(i=2;i<=n/2;i++)
{
if(n%i==0)
{
count=1;
break;
}
}
if(count==0)
System.out.println("prime number "+n);
else
System.out.println("not a prime number "+n);
}
}

7. import java.util.Scanner;
class Prime{
public static void main(String ar[]){
Scanner obj=new Scanner(System.in);
int num,i;
System.out.println("enter the value of number");
num=obj.nextInt();
for(i=2;i<=num/2;i++){
if(num%i==0){
System.out.println("not prime");

}
else{
System.out.println("prime");
break;}
}
}
}

8. import java.util.Scanner;

public static void main(String ar[]){

Scanner scan=new Scanner(System.in);
int num,temp=0;
System.out.println("Enter number");
num=scan.nextInt();

for(int i=2;i<=num;i++){
if(num%i==0){
temp=1;
break;
}
}
if(temp==1){
System.out.println("No. is not Prime");

}else{
System.out.println("No. is Prime");
}

}

}