Convert array of Strings to Array list

Question

I have a String array with name and id, I need to convert that String array to List of objects.

This is my code:

private List<ObjectAttribute> getDtls(String newVal) {
    ObjectAttribute object = new ObjectAttribute();
    List<ObjectAttribute> objLst = new ArrayList<ObjectAttribute>();
    String[] newImageVal = [step0005.jpg, 172B6846-0073-4E5B-B10A-DDD928994EA6, step0003.jpg, FBC8D143-2CD7-47E6-B323-31A0928A9338]
    for (int i = 0; i <= newImageVal.length - 1; i++) {
        object.setImageName(newImageVal[i]);
        object.setImageId(newImageVal[++i]);
        objLst.add(object);
    }
    return objLst;
}

but there is a problem that it always returns only the last value in objList. Can anyone correct this code.

nano_nano · Accepted Answer · 2019-05-28 11:15:21Z

3

move

ObjectAttribute object = new ObjectAttribute();

inside the for loop:

for (int i = 0; i <= newImageVal.length - 1; i++) {
    ObjectAttribute object = new ObjectAttribute();
    object.setImageName(newImageVal[i]);
    object.setImageId(newImageVal[++i]);
    objLst.add(object);
}

answered May 28, 2019 at 11:15

nano_nano

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6 Comments

Honza Zidek Over a year ago

It is a very bad practice to increment the for-loop variable again inside the for-loop body. You with your experience should not teach the beginners such things :)

Lino Over a year ago

@HonzaZidek that's an error from OP which was just copy pasted. So you don't have to tell StefanBeike but the OP instead ;)

Honza Zidek Over a year ago

@Lino: I think that we have a certain responsibility in our answers. We should fix not only their functional errors, but also their design errors. SO answers are very often used by beginners as a source of knowledge.

Lino Over a year ago

@HonzaZidek you're free to post your own answer, which points that out. SO encourages different answers, which all answer the same thing in different ways. And if you even improve the code from OP it will possibly get a lot of positive feedback

nano_nano Over a year ago

@Honza Zidek yes of course..., but my answer relates to the original problem. not to some code style guide issues or best practices.

|

sandeep gupta · Accepted Answer · 2019-05-28 11:17:59Z

1

private List<ObjectAttribute> getDtls(String newVal) {
    List<ObjectAttribute> objLst = new ArrayList<ObjectAttribute>();
    String[] newImageVal = [step0005.jpg, 172B6846-0073-4E5B-B10A-DDD928994EA6, step0003.jpg, FBC8D143-2CD7-47E6-B323-31A0928A9338]
//  String delimiter = ", ";
//  newImageVal = newVal.split(delimiter);
    for (int i = 0; i <= newImageVal.length - 1; i++) {
        ObjectAttribute object = new ObjectAttribute();
        object.setImageName(newImageVal[i]);
        object.setImageId(newImageVal[++i]);
        objLst.add(object);
    }
    return objLst;
}

answered May 28, 2019 at 11:17

sandeep gupta

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2 Comments

Honza Zidek Over a year ago

It is a very bad practice to increment the for-loop variable again inside the for-loop body. This should not be the accepted solution as other SO users use them as model solutions..

Honza Zidek Over a year ago

Also the condition i <= newImageVal.length - 1 is too optimistic, if the newImageVal does not contain an even number of elements, it will throw ArrayIndexOutOfBoundException.

Honza Zidek · Accepted Answer · 2019-05-28 11:56:11Z

1

The root cause of your problem is, as @StefanBeike wrote, that you instantiate the object only once before the for-loop and then you just keep rewriting its attributes. Moving the instantiation (= calling of new) inside the for-loop fixes the functionality.

However, apart from this, it is a very bad practice to increment the for-loop variable inside the for-loop body. Thus you obscure your intention and you will get a code which is less readable, harder maintainable and easier to break by later changes.

And the main condition should be i < newImageVal.length-1 to handle the array size safely. (To be 100% sure you do not get ArrayIndexOutOfBoundsException.)

There are multiple better ways.

Increment by 2 in the for-loop "header":

for (int i = 0; i < newImageVal.length-1; i += 2) {
    ObjectAttribute object = new ObjectAttribute();
    object.setImageName(newImageVal[i]);
    object.setImageId(newImageVal[i+1]);
    objLst.add(object);
}

Use while-loop instead of for-loop:

int i = 0;
while (i < newImageVal.length-1) {
    ObjectAttribute object = new ObjectAttribute();
    object.setImageName(newImageVal[i++]);
    object.setImageId(newImageVal[i++]);
    objLst.add(object);
}

edited May 28, 2019 at 11:56

answered May 28, 2019 at 11:49

Honza Zidek

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1 Comment

Lino Over a year ago

Maybe it's a mistake from OP, seems quite special to increase the i at two different places. But anyway. Good answer +1 :)

Sergey Benner · Accepted Answer · 2019-05-28 11:49:43Z

0

or you may do something like this using the streams way:

AtomicInteger ai = new AtomicInteger(); 
List<ObjectAttribute> objLst = Arrays.stream(newImageVal)
.map(img-> {
   ObjectAttribute object = new ObjectAttribute();
   object.setImageName(img);
   object.setImageId(ai.getAndIncrement()); 
   return obj;
 }).collect(Collectors.toList())

edited May 28, 2019 at 11:49

answered May 28, 2019 at 11:27

Sergey Benner

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