Akarlsen -4 years ago 94
Java Question

# Working with two unknown integers

Can't find out how to go further when working with two unknown integers in parameters. Have several tasks regarding this.

• returning the sum between two unknown integers, the two unknown numbers have to be included in the calculation as well

• returning the even numbers between the two unknown

• returning the odd numbers between the two unknown

• returning the prime numbers between the two unknown

I know this probably is very easy, but still can't find out how to get started.

``````public int method(int a, int b){
sum = 0;
??for() {
}??
``````

Answer Source
``````public static void main(String[] args) {
System.out.println("sum: " + sum(10, 12));
System.out.println("evens: " + evens(10, 20));
System.out.println("odds: " + odds(10, 20));
System.out.println("primes: " + primes(0, 100));
}

public static int sum(int from, int to) {
int sum = 0;

for (int i = from; i <= to; i++) {
sum += i;
}

return sum;
}

public static List<Integer> evens(int from, int to) {
List<Integer> evens = new ArrayList<>();

if (from % 2 != 0) {
from++;
}

for (int i = from; i <= to; i += 2) {
evens.add(i);
}

return evens;
}

public static List<Integer> odds(int from, int to) {
List<Integer> odds = new ArrayList<>();

if (from % 2 == 0) {
from++;
}

for (int i = from; i <= to; i += 2) {
odds.add(i);
}

return odds;
}

public static List<Integer> primes(int from, int to) {
List<Integer> primes = new ArrayList<>();
boolean prime = false;

for (int i = from; i <= to; i++) {
if (isPrime(i)) {
primes.add(i);
}
}

return primes;
}

public static boolean isPrime(int n) {
for(int i = 2; 2 * i < n; i++) {
if(n % i == 0) {
return false;
}
}
return true;
}
``````
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