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Thread: how to add a new entry in a current array

  1. #1
    Java kindergarten chronoz13's Avatar
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    Default how to add a new entry in a current array

    a liitle bit of program that demonstrates how to add a new entry in a current array that has current values

    public class ArraySampleExtendingIndex {
     
        private static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
     
        public static void main(String[] args) throws IOException {
     
            boolean insertNew = false,
                    newEntry;
     
            int[] numbers = {10, 2},
                  temp;
     
            int length = numbers.length;
     
            System.out.print("The Current Values Are: ");
            System.out.print("[");
     
            // display the current values
            for (int x = 0; x <= numbers.length - 1; x++) {
     
                System.out.print(numbers[x]);
     
                if (x < numbers.length - 1) {
     
                    System.out.print(", ");
                }
            }
     
            System.out.print("]");
            System.out.print("\n\n");
     
            do {
     
                System.out.print("Add New Entry ? ");
                String response = br.readLine();
     
                if (response.equalsIgnoreCase("Y")) {
     
                    System.out.print("Enter Your New Entry: ");
                    int entry = Integer.parseInt(br.readLine());
     
                    temp = new int[length];
                    newEntry = true;
     
                    // assign the values in the temporary array corresponding to its last position
                    for (int x = 0 ; x <= length - 1; x++) {
     
                        temp[x] = numbers[x];
                    }
     
                    // make an update to the value of the length, dont just add 1
                    length++;
     
                    numbers = new int[length];
     
                    // add the new entry in the last index
                    for (int i = length - 1; i >= 0; i--) {
     
                        if (newEntry == true) {
     
                            numbers[i] = entry;
                            newEntry = false;
                        }
                        else {
     
                            numbers[i] = temp[i];
                        }
                    }
     
                    System.out.print("\n");
                    System.out.println("New Entry Has Been Added.");
                    System.out.print("\n");
     
                    insertNew = true;
                }
                else {
     
                    insertNew = false;
                }
     
            }
            while (insertNew);
     
            System.out.print("\n");
     
            System.out.print("Current Value Are: ");
            System.out.print("[");
     
            // display the array together with the added values
            for (int x = 0; x <= numbers.length - 1; x++) {
     
                System.out.print(numbers[x]);
     
                if (x < numbers.length - 1) {
     
                    System.out.print(", ");
                }
            }
     
            System.out.print("]");
            System.out.print("\n");
        }
    }

  2. The Following User Says Thank You to chronoz13 For This Useful Post:

    JavaPF (December 28th, 2009)


  3. #2
    Super Moderator helloworld922's Avatar
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    Default Re: how to add a new entry in a current array

    FYI, it is much more efficient to allocate an array with double the current size when the limit is reached. This is because each time you allocate a new array, you have to first find the memory space for that array and allocate it, then re-populate the array with the values in the original array, a very time consuming process. I believe this is actually how the ArrayList and Vector classes increase their size (or, it may be some other function that's greater than 1).

  4. The Following User Says Thank You to helloworld922 For This Useful Post:

    chronoz13 (December 28th, 2009)

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