Find Prime numbers in an array of ’n’ elements (command line arguments) Java

We have all learned the logic behind prime numbers, and now our task is to accept an array from the user via command-line arguments and find the prime numbers among those elements.

Let's see the output so that we can get fired up from the inside.

E:>java PNumbersInArray.java 3 4 5 6 7 8 9 10 12 13
3
5
7
13

As you can see we get the prime numbers from the above-mentioned array.

Java Code

class PNumbersInArray{
public static void main(String[] args){
for(String arg: args){
int num = Integer.parseInt(arg);
if(isPrime(num)>0){
System.out.println(num+" ");
}
}
}

public static int isPrime(int num){
if(num <=1){
return 0;
}
for(int i=2; i<=num; i++){
if(num % i == 0){
return 0;
}
}
return num;
}
}

How to get Input from Command line argument in Java

public static void main(String[] args){
for(String arg: args){
int num = Integer.parseInt(arg);

This piece of code is designed to receive input from command-line arguments. In the main method, we declare an array of String types named args.

Using a for-each loop, we iterate through the args elements one by one, assigning each element to the variable arg.

In the third line, each element is converted from a string to an integer.

How the isPrime() function is going to work?

public static int isPrime(int num){
if(num <=1){
return 0;
}
for(int i=2; i<=num; i++){
if(num % i == 0){
return 0;
}
}
return num;
}
}

In the condition ‘if (num ≤ 1),’ we check whether the number is less than or equal to one. If it is, we know that it will never be a prime number, so we return false.

for(int i=2; i<=num; i++){
if(num % i == 0){
return 0;
}
}

The above code is used to find prime numbers in the array elements.

Time Complexity O(n²)