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Thread: array numbers

  1. #1
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    Default array numbers

    Hello,
    For my Java class I have to create an array. I won't know how many numbers will be input into the array. So far on the youtube videos I've seen, to create an array, they always seem to know how many numbers their want to store. So their examples are

    Double nameOfArray[] = new Double[10];

    so the array named nameOfArray will be an array using the Double type of number, and will have 10 values.

    I have to create an array in which I don't know how many values, because the user will be inputting values from ( I assume ) the Scanner. For now to get around this, my array looks like

    Double salesForWeek[] = new Double[900000];

    Is there a better way to make this array? Also, I'm assuming I would need to use the Scanner since I need to prompt the user for the number. Is that a correct assumption?
    Any help will be greatly appreciated.

  2. #2
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    Default Re: array numbers

    For dynamically sized array, you could use ArrayList:

    import java.util.Scanner;
    import java.util.ArrayList;
     
    class MyArray {
    	public static void main(String[] args) {
    		ArrayList<Integer> array = new ArrayList<Integer>();
    		Scanner buf = new Scanner(System.in);
    		int input;
    		while(buf.hasNextInt()) {	//enter non-integer to exit loop
    			input = buf.nextInt();
    			array.add(input);	// use array.add() to append item to array 
    		}
    		System.out.println("Size of array is " + array.size());
    		for(int i=0; i<array.size(); i++) {
    			// use array.get(int index) instead of array[int index]
    			System.out.println("array[" + i + "] = " + array.get(i));
    		}
     
    	}
    }

    ArrayList documentation

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    Default Re: array numbers

    You can also prompt for an array size and then use that in your declaration for the array. However, unless you are required to use arrays, the best method is what dboxall123 said. Use ArrayList.

    Regards,
    Jim

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    Default Re: array numbers

    Awesome! thank you some much for the help. I'll try the ArrayList.

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