Java - Modify String Array to ArrayList<String>

Question

int currentKeySize=8;

String message = new String();
message="This is a test message";   
String[] splitMessage = new String[currentKeySize];
Arrays.fill(splitMessage,"");

for (int i = 0; i < message.length(); ++i) {            
    splitMessage[i % splitMessage.length] += message.charAt(i);         
}
for (int i = 0; i < splitMessage.length; ++i) { 
    System.out.println(splitMessage[i]);
}

This code takes a message and splits it into an array of size 8, one character at the time so char(0) goes to String(0)...char(7) to String(7) and char(8) back to String(0).

I have whole program working around this concept and it is great...however now I have to dynamically modify currentKeySize,preferably using 'for' loop so it goes from 1 or 2 (number of splits) to n (lets say 20 splits).

I am aware of ArrayList< String >, however I did not have much luck with it as it is pretty new concept to me.I cannot figure out how to make it work in similar fashion to what I have here with appending characters.

Could someone demonstrate correct use of ArrayList< String >(did not accept without spaces between <>) to perform the same way as what is posted above?

Any help will be appreciated!

SOLVED. Thanks to micneer for exactly what I asked for =).

Answer 1

You can try like this, wish help you.

    int currentKeySize = 8;

    String message = new String();
    message="This is a test message";   
    List<String> list = new ArrayList<String>();

    for (int i = 0; i < currentKeySize; ++i) {
        list.add(i % currentKeySize, "");
    }
    for (int i = 0; i < message.length(); ++i) {      
        list.set(i % currentKeySize, list.get(i % currentKeySize) + message.charAt(i));
    }
    for (int i = 0; i < list.size(); ++i) { 
        System.out.println(list.get(i));
    }

Answer 2

You can simply add your split string into ArrayList:

Initialize list as following:

List<String> list=new ArrayList<String>();

And later on add to it as follwing:

list.add(spiltString);

The ArrayList class extends AbstractList and implements the List interface. ArrayList supports dynamic arrays that can grow as needed.

Standard Java arrays are of a fixed length. After arrays are created, they cannot grow or shrink, which means that you must know in advance how many elements an array will hold.

Array lists are created with an initial size. When this size is exceeded, the collection is automatically enlarged. When objects are removed, the array may be shrunk.

Answer 3

You can do this.So you do not have to worry about initial size.

  String message = new String("This is a test message");
  String[] splitMessage =message.split("");

Answer 4

public static void main(String[] args) {
    int currentKeySize=8;

    String EMPTY_STRING = "";
    String message = new String();
    message="This is a test message";   
    List<String> splitMessage = new ArrayList<String>();
    Collections.fill(splitMessage, EMPTY_STRING);
    for (int i = 0; i < message.length(); ++i) {            
        try {
            String str = splitMessage.get(i%currentKeySize) + message.charAt(i); 
            splitMessage.set(i%currentKeySize, str);
        } catch(IndexOutOfBoundsException e) {
            //Adding EMPTY_STRING will convert character to String.
            splitMessage.add(EMPTY_STRING+message.charAt(i));
        }
    }
    System.out.println(splitMessage);
}

I think this piece of code will solve your problem.