Number is Prime or not -Python & Java

Python

a= 31
flag = False
for i in range(2,a//2):
if a%i==0:
flag=True
break
if flag==False:
print("number is prime")
else:
print("Not Prime")

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Java

public class test1 {
    static boolean isPrime(int num){
        if(num==0||num==1)
            return false;
        for(int i=2;i<num;i++){
            if(num%i==0){
                return false;
            }
        }
        return true;
    }
    public static void main(String[] args) {

        int num = 10;
        for(int i=0;i<num;i++){
            if(isPrime(i)==true){
                System.out.println(i);
            }
        }
    }
}

public class test1 {

    public static void main(String[] args) {

        int num = 20;
        int flag=0;
        for(int i=2;i<=num/2;i++){
            if(num%i==0){
                System.out.println("number is not prime");
                flag =1;
                break;
            }
        }
        if(flag==0){
            System.out.println("number is prime");
        }

    }
}