Write a program to input any n numbers in a single dimensional array arr[], now store all the prime numbers in the array prim[] and all the composite numbers in the array com[]. Display the contents of both the arrays prim[] and com[].

**Program:**

```
import java.io.*;
class Arrange{
public static void main(String args[])
throws IOException{
InputStreamReader in = new InputStreamReader(System.in);
BufferedReader br = new BufferedReader(in);
System.out.print("Number of elements: ");
int n = Integer.parseInt(br.readLine());
int arr[] = new int[n];
int i = 0;
int j = 0;
int k = 0;
int countc = 0;
int countp = 0;
for(i = 0; i < arr.length; i++){
System.out.print("Enter element: ");
arr[i] = Integer.parseInt(br.readLine());
if(isPrime(arr[i]))
countp++;
else
countc++;
}
int prim[] = new int[countp];
int com[] = new int[countc];
for(i = 0; i < arr.length; i++){
if(isPrime(arr[i]))
prim[j++] = arr[i];
else
com[k++] = arr[i];
}
System.out.println("Prime Numbers:");
for(i = 0; i < prim.length; i++)
System.out.print(prim[i] + "\t");
System.out.println("\nComposite Numbers:");
for(i = 0; i < com.length; i++)
System.out.print(com[i] + "\t");
}
public static boolean isPrime(int n){
int f = 0;
for(int i = 1; i <= n; i++)
if(n % i == 0)
f++;
if(f == 2)
return true;
return false;
}
}
```

## 4 replies on “Separating Composite and Prime Numbers in Java”

Sir,in the above program,the output is showing like this:

Number of elements: 10

Enter element: 1

Enter element: 2

Enter element: 3

Enter element: 4

Enter element: 5

Enter element: 6

Enter element: 7

Enter element: 8

Enter element: 9

Enter element: 10

Prime Numbers:

2 3 5 7

Composite Numbers:

1 4 6 8 9 10

As you have told 1 is neither prime nor composite but 1 is being displayed in the composite array.Sir,can you please explain why is it so?

In that case, write a separate if statement for 1 to avoid putting it in the array.

Sir,In the above program if we accept 1 as element of the array,in which array will it display prime or composite?

1 is unique. It is neither prime nor composite.