What Exception to throw if (arg1 > arg2) should be fulfilled?

Question

I do not really have a problem to solve, I would just like to know if there is a common way to deal with the following:

I have a constructor that takes two arguments (both int). The constructor itself only initializes attributes of my object. However, if (arg1 > arg2) is not fulfilled, there will be problems later on. Therefore I want to throw an Exception here because this is the place where a potential problem originates.

Is there a common Exception to throw in this case? Or would you rather throw a custom Exception ? If so, how would you call that?

Answer 1

Is there a common Exception to throw in this case?

According to the documentation , an IllegalArgumentException can be thrown:

Thrown to indicate that a method has been passed an illegal or inappropriate argument .

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Or would you rather throw a custom Exception ?

It's not the case for throwing own exception unless you already have one and there are a few similar situations where you have thrown it.

Try to answer the following questions, they are gonna point you to the answer:

• Is that an important case to handle?
• Is that a usual validation case?
• Will I encounter similar cases later?

Answer 2

This is a good reason to use IllegalArgumentException . You can use it in your class that way:

class YourClass {
    int first, second;
    YourClass(int first, int second) {
        if(first <= second) {
            throw new IllegalArgumentException("First argument has to be higher than second, arguments passed: " + first + ", " + second);
        }
        this.first = first;
        this.second = second;
    } 
}