Adding new element into a fixed array

Question

I did search on internet, but still don't understand, so I ask this question here.

in the small program below, I created two tour instance, all I want to do is putting tour[2] in without changing "Tour tour[]=new Tour[2];".

A lot of people recommend ArrayList, but I don't know how to do it in this code.

class Test{
public static void main(String args[]){

    class Tour{
        private String tourId;
        private String tourDescription;
        private double tourFee;
        private int numOfBooking;

        public Tour(String tourId,String tourDescription,double tourFee){
            this.tourId=tourId;
            this.tourDescription=tourDescription;
            this.tourFee=tourFee;
        }

        public void print(){
            System.out.println("ID:"+this.tourId);
            System.out.println("Desc:"+this.tourDescription);
            System.out.println("Fee:"+this.tourFee);
        }
    }


    Tour tour[]=new Tour[2];
    tour[0]=new Tour("AB001","TOUR1",100);
    tour[1]=new Tour("AB002","TOUR2",200);
}
}

wattostudios · Accepted Answer · 2012-05-26 07:41:25Z

1

As you discovered, arrays are indeed fixed length, and as such I would definitely recommend an ArrayList. Use it like this...

ArrayList<Tour> tours = new ArrayList<Tour>();
tours.add(new Tour("AB001","TOUR1",100));
tours.add(new Tour("AB002","TOUR2",200));

Every time you want to add a new Tour, just call tours.add() again.

answered May 26, 2012 at 7:41

wattostudios

8,79013 gold badges45 silver badges58 bronze badges

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

3 Comments

Qin Over a year ago

the problem is, the actual code is longer than this, and have a different functions, if I change the code like you said, I think I need to change most of the program?

Louis Wasserman Over a year ago

You don't have much of a choice. You can't change the length of an array.

wattostudios Over a year ago

Yeah its a bit annoying, but once you know how to do it, you'll remember it from now on, and you'll never create the same problem again :-) If you've got a lot of them, try using find/replace in your editor so that you minimise the number of changes.

Hayden · Accepted Answer · 2012-05-26 07:41:58Z

1

When you create an array in java like Tour tour[] = new Tour[2] this means you can only add 2 elements to it.

To implement this using an ArrayList you would:

In you import statements add

import java.util.ArrayList

Then replace your array code with this

ArrayList<Tour> tour = new ArrayList<Tour>();
tour.add(new Tour("AB001", "TOUR1", 100);
tour.add(new Tour("AB002", "TOUR2", 200);
tour.add(new Tour("AB003", "TOUR3", 300);

answered May 26, 2012 at 7:41

Hayden

2,8082 gold badges24 silver badges30 bronze badges

Comments

Jeremy Goodell · Accepted Answer · 2012-05-26 07:40:33Z

0

If you're trying to add a tour[2], then your array needs three elements, right?

Otherwise:

List<Tour> tour = new ArrayList<Tour>();
tour.add(new Tour("AB001", "TOUR1", 100);
tour.add(new Tour("AB002", "TOUR2", 200);
tour.add(new Tour("AB003", "TOUR3", 300);

answered May 26, 2012 at 7:40

Jeremy Goodell

19.1k5 gold badges37 silver badges54 bronze badges

Comments

FThompson · Accepted Answer · 2012-05-26 07:41:33Z

0

As your array scenario is impossible, here's how to do the same process with an array list:

ArrayList<Tour> tours = new ArrayList<Tour>();
tours.add(new Tour("AB001","TOUR1",100));
tours.add(new Tour("AB002","TOUR2",200));
tours.add(/*another tour, and so forth*/);
// to convert to a Tour[], use the following:
Tour[] tourArray = tours.toArray(new Tour[tours.size()]);

ArrayList's are extremely useful in cases where the size of the data set is unknown.

answered May 26, 2012 at 7:41

FThompson

28.8k13 gold badges63 silver badges95 bronze badges

Comments

fahim ayat · Accepted Answer · 2012-05-26 07:41:47Z

0

using array list is simple, you have this code :

Tour tour[]=new Tour[2];
tour[0]=new Tour("AB001","TOUR1",100);
tour[1]=new Tour("AB002","TOUR2",200);

replace it with this :

ArrayList<Tour> tours = new ArrayList<Tour>();
tours.add(new Tour("AB001","TOUR1",100));
tours.add(new Tour("AB002","TOUR2",200));

to get elements arrayList , simply use tour.get( index ) ;

answered May 26, 2012 at 7:41

fahim ayat

3125 silver badges10 bronze badges

Comments

Tom · Accepted Answer · 2012-05-26 07:42:36Z

0

They are right about the ArrayList; use it like this:

List<Tour> tours = new ArrayList<Tour>();
tours.add(new Tour("AB001","TOUR1",100));
tours.add(new Tour("AB002","TOUR2",200));

you will need to import java.util.*

answered May 26, 2012 at 7:42

Tom

4,1702 gold badges26 silver badges40 bronze badges

Comments

Ravinder Reddy · Accepted Answer · 2012-05-26 07:46:24Z

0

This is not possible unless assigned new. Because primitive arrays are not expandable.
Alternatively you can use collections to dynamically add a new object to the list.
An example is shown below:

List<Tour> tourList = new ArrayList<Tour>( 10 );  
tourList.add( 0, new Tour( "AB001", "TOUR1", 100 ) ); // add at first    
tourList.add( 1, new Tour( "AB002", "TOUR2", 200 ) ); // add next to first

This way you can add any number of Tour instances at any position of the list.
And you may want to convert the tourList back to a primitive array of Tour
For that you need following code:

Tour [] toursArray = new Tour[ tourList.size() ];
tourList.toArray( toursArray );

answered May 26, 2012 at 7:46

Ravinder Reddy

24.1k6 gold badges54 silver badges86 bronze badges

Comments

amit · Accepted Answer · 2012-05-26 07:46:29Z

0

You cannot do it in with arrays, since their length are fixed.
Your question pretty much shows the alternatives already:

Use an ArrayList
Create a new instacne of the array

The ArrayList is actually an implementation of a dynamic array in java, and this is most likely what you actually want.

Instantiate it with a default constructor, and add elements with ArrayList.add(index,element) to add elements in specific location or with ArrayList.add(element) to append elements.

code snap:

List<Tour> tours = new ArrayList<Tour>();
tours.add(new Tour("AB001","TOUR1",100));
tours.add(new Tour("AB001","TOUR1",100));

You can keep appending elements using ArrayList.add(element)

edited May 26, 2012 at 7:46

answered May 26, 2012 at 7:40

amit

179k27 gold badges245 silver badges348 bronze badges

Collectives™ on Stack Overflow

Adding new element into a fixed array

8 Answers 8

3 Comments

Comments

Comments

Comments

Comments

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

8 Answers 8

3 Comments

Comments

Comments

Comments

Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related