return with while and if else loop

Question

I've the below method which expects a return type as SomeObject. mapData() function returns SomeObject. I want to come out from the loop as soon as one condition gets satisfied. I'm getting compilation error due to no return type found. Can you please point out the issue with my condition ?

 public static SomeObject mapper(List<String> mylist) {
    Iterator iter = mylist.iterator();
    while (iter.hasNext()) {
        Object[] result = (Object[]) iter.next();
            if (condition){
                //dosomething
                return mapData(abc);
            }else if (condition) {
                //dosomething
                return mapData(def);
            }else {
                //dosomething
                return mapData(ghi);
            }
    }
  // Get compilation error due to no return type at this position
}

You can add a return null; after the while loop. Geez... Now looking how people crawl for rep. — Luiggi Mendoza
– Luiggi Mendoza, Commented Jun 21, 2013 at 22:04

Rohit Jain · Accepted Answer · 2013-06-21 22:10:36Z

4

Imagine what happens when your while loop never executes? This will happen if your list is empty. In that case, your method would not return anything, thus the error.

Just add a return statement:

return null;

after your while loop. Or return some default instance of SomeObject, if you haven't done the null check for the value returned by this method.

edited Jun 21, 2013 at 22:10

answered Jun 21, 2013 at 22:05

Rohit Jain

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2 Comments

Luiggi Mendoza Over a year ago

@PravatPanda in fact, returning a null is a design matter as discussed here. IMO I would prefer to evaluate if the method should return null or not instead of just setting a return null at the bottom. And if you prefer to not return anything at all after the while loop, you can throw an exception (or a RuntimeException if want to be silent) and handle the exception in the caller as explained in arshajii answer which can lead to another design.

Rohit Jain Over a year ago

@LuiggiMendoza. True. Should have added this earlier. Thnx :)

arshajii · Accepted Answer · 2013-06-21 22:06:08Z

3

The compiler requires that all possible code paths either

return a value
throw an exception

You should do whichever makes more sense in the context of your program, in your case that means adding one of these statements to the end of your method.

answered Jun 21, 2013 at 22:06

arshajii

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Comments

kosa · Accepted Answer · 2013-06-21 22:05:01Z

0

Add return null; (or) relevant return statement at the end.

If none of the conditions satisfied in your while loop, then this will be returned.

answered Jun 21, 2013 at 22:05

kosa

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