PrimeNumber.java

//pseudocode 
START
  SET number = (given number)
  SET isPrime = true

  IF number < 2 THEN
    isPrime = false
  ELSE
    FOR i = 2 TO number - 1
      IF number MOD i == 0 THEN
        isPrime = false
        BREAK
      END IF
    END FOR
  END IF

  IF isPrime THEN PRINT number + " is prime"
  ELSE PRINT number + " is not prime"

  PRINT "Prime numbers between 1 and " + number + ":"
  FOR n = 2 TO number
    SET prime = true
    FOR i = 2 TO n - 1
      IF n MOD i == 0 THEN prime = false
    END FOR
    IF prime THEN PRINT n
  END FOR
END


public class PrimeNumber {
    public static void main(String[] args) {

        int number = 20;

        // ── CHECK IF NUMBER ITSELF IS PRIME ──
        boolean isPrime = true;

        if (number < 2) {
            isPrime = false;
        } else {
            for (int value = 2; value < number; value++) {  // FIXED: i → value
                if (number % value == 0) {
                    isPrime = false;
                    break;
                }
            }
        }

        if (isPrime) {
            System.out.println(number + " is a prime number.");
        } else {
            System.out.println(number + " is NOT a prime number.");
        }

        // ── PRINT ALL PRIMES BETWEEN 1 AND number ──
        System.out.println("Prime numbers between 1 and " + number + ":");

        for (int count = 2; count <= number; count++) {       // FIXED: n++ → count++
            boolean prime = true;

            for (int counter = 2; counter < count; counter++) { // FIXED: i,n → counter,count
                if (count % counter == 0) {                     // FIXED: n,i → count,counter
                    prime = false;
                    break;
                }
            }

            if (prime) System.out.print(count + " ");           // FIXED: n → count
        }
    }
}                                                               // FIXED: removed extra }}
```

---

# What Each Variable Does

| Variable | Role | Example |
|---|---|---|
| `number` | The target number given | 20 |
| `value` | Tests if `number` itself is prime | counts 2, 3, 4 ... 19 |
| `count` | Outer loop — each number being tested | 2, 3, 4 ... 20 |
| `counter` | Inner loop — checks divisors of `count` | 2, 3, 4 ... |
| `isPrime` | Is the main `number` prime? | true/false |
| `prime` | Is the current `count` prime? | true/false |

---

# Sample Output
```
20 is NOT a prime number.
Prime numbers between 1 and 20:
2 3 5 7 11 13 17 19