I'm new Java and are currently reading a course at university. We're using Java programming early objects as course literature. I have a question about constructors for new objects.
The book states very clearly "Even though it’s possible to do so, do not call methods from constructors."

Is this for all methods, period? I understand the problem with calling the class own instance method from constructor. But helper methods, etc?

I made up a small example.

Here is an example of a class that needs one integer in its constructor. The integer needs to be greater than one.

Would this be acceptable? If not, I guess you can't use any of Java Math util function or anything like that in the constructor?

```java
public class TestClass {

    private int number;

    // Only allow construction if number is greater than one
    TestClass(int number) {
        if (NumberUtils.isGreaterThanOne(number)) {
            this.number = number;
        } else {
            throw new IllegalArgumentException("Number must be above 1");
        }
    }
}

```

```java
public class NumberUtils {

    // Helper method to check if number is greater than one
    public static boolean isGreaterThanOne(int number) {
        return number > 1;
    }
}

```