Philip Drach - 1 year ago 67

Java Question

I am practicing my Java and working on a program that will sum up all of the integers from 1 to 999 that are either a multiple of 3 or a multiple of 5.

Here is what I've written so far:

`public class MultiplesOfThreeAndFive {`

public static void main(String[] args) {

//For a number to be a multiple, i % number equals 0.

MultiplesOfThreeAndFive m = new MultiplesOfThreeAndFive();

for (int i = 1; i < 1000; i++){

System.out.println(m.checkIfMult(i));

}

}

public boolean checkIfMult(int i){

return (i % 3 == 0 || i % 5 == 0);

}

}

Now when I compile this, all I get is true and false for each number from 1 to 999. I understand that this is because my method return type for my

`checkIfMult`

method is boolean.

I can't sum up true and false so I want to only acquire those numbers that display as true in the list.

EDIT:

Going by what Tom said...I added this to my main method:

`public static void main(String[] args) {`

//For a number to be a multiple, i % number equals 0.

MultiplesOfThreeAndFive m = new MultiplesOfThreeAndFive();

for (int i = 1; i < 1000; i++){

System.out.println(m.checkIfMult(i));

if (m.checkIfMult(i) == true){

}

}

}

Answer

You can keep a running sum like this:

```
public class MultiplesOfThreeAndFive {
public static void main(String[] args) {
//For a number to be a multiple, i % number equals 0.
MultiplesOfThreeAndFive m = new MultiplesOfThreeAndFive();
int sum = 0;
for (int i = 1; i < 1000; i++){
if (m.checkIfMult(i))
{
sum = sum + i;
}
}
System.out.println("Sum is: " + sum);
}
public boolean checkIfMult(int i){
return (i % 3 == 0 || i % 5 == 0);
}
}
```

**Side Note**: You can make the `checkIfMult`

method static in this example. If you do so, then you don't need to create an instance of the `MultiplesOfThreeAndFive`

class.

Source (Stackoverflow)