CODEWITHSUNDEEP
java
Michael
Michael

Reputation: 1397

Java template for checking that value was set

In Java I have a bunch of variables (of different types) that I would like to check that they have been set before using them, and if they have not then the result is always the same and I want to throw an error that'll be caught higher up. In theory the code is designed that this should NEVER happen, but the consequences of a bug making it happen are too great to leave it to just unit testing.

I was thinking of just making a template that has a get() and set() function. The set would set the value and set a boolean to let it know it has been set and the get() would check the boolean and return the value or throw an error. something like:

Class ImportantInfo<T> {
   private T t;
   private beenSet = false;
   public T get(){
      if(beenSet) return t;
      else throw error;
   }
   public void set(T value){
    t =value;
    beenSet = true;
   }
}

Is this the correct and best approach? Are there other, possibly better, ways? I worry I am over engineering the solution or that a template this straightforward might already exist in Java?

Upvotes: 2

Views: 113

Answers (2)

fdsa
fdsa

Reputation: 1409

One approach to do this would be to use Java Optionals. Optionals represent a value that may or may not be present.

  • Optional.empty() represents a value that is not present
  • The .get() method gets a value if it is present
  • The isPresent() checks if a value has been set or not.

The main advantage of using Optional over simply checking for null is that optional forces you to use .get() so you don't accidentally call a null value that hasn't been set.

In your particular case, I would initialize all the values at the top of the class to Optional.empty() and then use .isPresent to make sure they were set.

Note: This will only work with Java 8

(Apparently Guava Optional will work in versions less than 8 (see Tom's comment - I have no experience with this)

Upvotes: 3

nafas
nafas

Reputation: 5423

there are many ways, but the approaches that I would normally find useful:

  1. checking if its null, personally I just use this, if null I assume its not been set otherwise its been set, then you can also give the user the responsibilities (optional)

  2. instead of having setter method, you can use the constructor. this way you ensure that the value has been set before even being able to use the get method.

Upvotes: 1

Related Questions