Category: Sample Program in Java

Sample Program

What is prime number ? Write a program in Java to find prime numbers from a list of numbers


Java prime number program

A prime number (or a prime) is a natural number greater than 1 that has no positive divisors other than 1 and itself. A natural number greater than 1 that is not a prime number is called a composite number.
Java prime number program is given bellow:

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import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;

public class PrimeNumber {

public static void main(String[] args) throws IOException {

System.out.println("Series of Numbers Prime number calculation:");
int a;
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

System.out.println("Please enter the Series last number");
a = Integer.parseInt(br.readLine());

System.out.println("You entered :" + a);

int primeNumberFlag = 0;

List primeList = new ArrayList();
List notPrimeList = new ArrayList();

System.out.println("Series of nuumbers is ");
for (int i = 2; i <= a; i++) {
for (int j = 2; j <= i; j++) {
if ((i != j) && (i % j == 0)) {
primeNumberFlag = 1;
break;
} else {
primeNumberFlag = 0;
}
}

if (i != 2 && primeNumberFlag == 1) {
notPrimeList.add(i);
} else {
primeList.add(i);
}

System.out.print(i + " ");
}

System.out.println("");
System.out.println("Prime Number List from number 1 to " + a);

for (Integer primeL : primeList) {
System.out.print(primeL + " ");
}

System.out.println("");
System.out.println("Not Prime Number List from number 1 to " + a);

for (Integer notPrimeL : notPrimeList) {
System.out.print(notPrimeL + " ");

}

// If you want to test only a number is prime or not , you may use this code given bellow

/*
for (int i = 2; i <= a; i++) {
if (i == a) {
System.out.println(a + " is prime number");
} else {
if (a % i == 0) {
System.out.println(a + " is not prime");
break;
}
}
}

*/
}

}