Java avoid using too many if statement or too many validator classes

Question

I am using lot of if statements to check.Like:

if(statement 1){ 
   block 1;
}
if(statement 2){
   block 2;
}
...//about at least 20 if
if(statement n){
   block n;
}

To avoid using too many if-statement, I have tried to use strategy pattern which would create validator class for each if-statement.Like:

public interface Validator<SomeObejct>{
    public Result validate(SomeObject o);
 } 

public class SomeValidator implements Validator<SomeObject> {
   @Override
    public boolean validate(SomeObject o) throw Exception{
        if(statement 1){ 
            block 1;
         }  
}

Because I may have at least 20 if-statement, it may need at least 20 validator classes. So if there is any better solution for that? Or how can I manage these 20 validotor classes?

Edit:

To be more specific, I am writing some code for checking the problem on my schedule. For example:

 if(currentDate > mustFinishDate){
     warning();
 }
 if(NotScheduleADateForThisTask){
    warning();
 }
 if(DateFormatNotCorrect){
    error();
 }

Above the date check may also be the if-statement block.

Are you using the if statements to test for only one variable or multiple variables, post an example of what you verify with the if statements. — Precious Uwhubetine
– Precious Uwhubetine, Commented Jan 2, 2019 at 15:04
Tell us more about your exact task. 20 if statements in a row sounds like a poor overall design. — PM 77-1
– PM 77-1, Commented Jan 2, 2019 at 15:05
Do you want to use your validators dynamically, or these are just 20 static 'if's? — aBnormaLz
– aBnormaLz, Commented Jan 2, 2019 at 15:06
If you have 20 completely distinct conditions, you will have 20 if statements, 20 classes, or 20 somethings. You can't just turn 20 conceptually different things into fewer than there actually are. — Michael
– Michael, Commented Jan 2, 2019 at 15:14
@Michael Thanks for your answer. In that case, I may need to think how to manage these 20 classes or 20 if statements in better way. — Kun Liu
– Kun Liu, Commented Jan 2, 2019 at 15:19

daniu · Accepted Answer · 2019-01-02 16:02:54Z

5

You can use the Composite pattern to maintain a list of all validators:

class ValidatorComposite<T> implements Validator<T> {
    List<Validator<T>> validators = new ArrayList<>();
    public void addValidator(Validator<T> add) { validators.add(add)); }

    public Result validate(T toValidate) {
        Result result = Result.OK;
        for (Validator<T> v : validators) {
            result = v.validate(toValidate);
            if (result != Result.OK) break;
        }
        return result;
    }
}

and since Validator only has one method, for Java 8 it's a functional interface, so you don't really need "20 classes" but can create a list on the fly using lambdas.

ValidatorComposite<SomeObject> val = new ValidatorComposite<>();
val.addValidator(so -> condition1 ? block1(so) : Result.OK);
val.addValidator(so -> condition2 ? block2(so) : Result.OK);

and so on.

Your code sample isn't really consistent because first you declare Validator to return Result and later let the implementation return boolean (and even throws an Exception), so I kind of intergrated both by ignoring the exception and using a Result.OK value.

edited Jan 2, 2019 at 16:02

answered Jan 2, 2019 at 15:34

daniu

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2 Comments

Kun Liu Over a year ago

Thanks for your answer. It inspire me a lot. I think this is a good way to manage my Validators.

Adalberto J. Brasaca Over a year ago

@daniu Is it mandatory that the variables values have already been initialized ?

Amir Hedieh · Accepted Answer · 2019-01-02 15:21:23Z

1

these days what you should not probably care about is performance because of power of computers. now most programmers try to write readable and clean codes.

so i believe if writing 20 ifs makes your code easier to understand and more flexible its not bad to implement that.

BTW you can use switch case too.

switch (variable){
     case 1:{
     //block 1
      }
      case 2:{
      //block2
      }
      ...
}

if your cases are not similar and have different aspects using that Validator pattern will lead to inflexibility(It may lead to this point, it depends on situation).

answered Jan 2, 2019 at 15:21

Amir Hedieh

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2 Comments

NickL Over a year ago

I agree with your first two points, but the switch case is not the same as OP's example. If you put in the breaks in each case, it behaves like a sequence of if-else-if's, not as a sequence of if's.

scottb Over a year ago

In many cases, particularly if the value of variable is set by code that you maintain, much more readable, concise, and maintainable code is achieved by replacing switch-case blocks by an enum with a constant specific method or stored lambda.

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