How would I remove an index from ArrayList after a return statement?

Question

I am working on an class lab and ran into some trouble. We have been asked to write a method with the following instructions:

"Dog getRandomDog() - randomly selects a dog, returns it, and removes it from the kennel. Returns null if there are no dogs."

This is the method that I wrote (which doesn't work):

public Dog getRandomDog(){
    if(dogs.size() >= 0){
        Random random = new Random();
        int index = random.nextInt(dogs.size());
        return dogs.get(index);
        dogs.remove(index);
   }
    else {
    return null;
   }
}

I do understand that you cant have an executable statement after a return, but then how the heck to do you around this? Thanks in advance.

MadProgrammer · Accepted Answer · 2013-04-20 05:37:28Z

3

I come from an old school of thought One entry, one exit

public Dog getRandomDog(){
    Dog dog = null;
    if(dogs.size() >= 0){
        Random random = new Random();
        int index = random.nextInt(dogs.size());
        dog = dogs.remove(index);
    }
    return dog;
}

This basically means that you allow one point of entry for your method (a little mute in Java) and one exit (or one return). This makes the method easier to understand as you don't need to worry about the method exiting half way through. Really a pain when the method can run several screens lengths...

answered Apr 20, 2013 at 5:37

MadProgrammer

348k22 gold badges243 silver badges379 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

masoud · Accepted Answer · 2013-04-20 05:35:35Z

1

After return the code will not run

return dogs.get(index);
dogs.remove(index);  // <--- This will not execute after return

Try to return the result of remove:

return dogs.remove(index);

answered Apr 20, 2013 at 5:35

masoud

56.8k18 gold badges152 silver badges214 bronze badges

Comments

shiladitya · Accepted Answer · 2013-04-20 05:37:05Z

1

dogs.remove(index) itself will remove the Dog object at index and return it as well.

return dogs.remove(index)

answered Apr 20, 2013 at 5:37

shiladitya

2,3101 gold badge24 silver badges37 bronze badges

Comments

PSR · Accepted Answer · 2013-04-20 05:35:42Z

0

You need to remove before the return statement

 public Dog getRandomDog(){
    Dog d = null;
    if(dogs.size() >= 0){
        Random random = new Random();
        int index = random.nextInt(dogs.size());
        d = dogs.remove(index);
    }
    return d;
    }

answered Apr 20, 2013 at 5:35

PSR

40.4k43 gold badges115 silver badges154 bronze badges

Comments

Santosh Kewat · Accepted Answer · 2013-04-20 05:39:30Z

0

If the collection that dogs is a type of returns the object itself on calling remove, you can simply do:

int index = random.nextInt(dogs.size()); return dogs.remove(index);

answered Apr 20, 2013 at 5:39

Santosh Kewat

5621 gold badge8 silver badges20 bronze badges

Comments

Michael Hall · Accepted Answer · 2013-04-20 05:41:58Z

0

The most compact version would be:

Dog d = dogs.remove(getRandomDog());  

public Dog getRandomDog()  {  
    return dogs.size() > 0 ?  dogs.get((int)(Math.random()*dogs.size())) : null;  
}

answered Apr 20, 2013 at 5:41

Michael Hall

1855 bronze badges

Comments

Jatin · Accepted Answer · 2013-04-20 05:45:01Z

0

This will also work, apart from most of the answers above

public Dog getRandomDog(){
if(!dogs.isEmpty()){
    Random random = new Random();
    int index = random.nextInt(dogs.size());
    try{
    return dogs.get(index);
    }finally{
    dogs.remove(index);
   }
}
 else {
  return null;
 }
}

answered Apr 20, 2013 at 5:45

Jatin

31.8k16 gold badges102 silver badges173 bronze badges

Comments

Jin Kwon · Accepted Answer · 2013-04-20 06:16:27Z

0

I voted up @MadProgrammer.

public Dog getRandomDog() {
    return dogs.isEmpty() ?
        null : dogs.remove(new Random().nextInt(dogs.size()));
}

answered Apr 20, 2013 at 6:16

Jin Kwon

22.4k18 gold badges133 silver badges219 bronze badges

Collectives™ on Stack Overflow

How would I remove an index from ArrayList after a return statement?

8 Answers 8

Comments

Comments

Comments

Comments

Comments

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

8 Answers 8

Comments

Comments

Comments

Comments

Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related