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Thread: Selection Sorting a text array

  1. #1
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    Default Selection Sorting a text array

    I have to use selection sort to sort out a list of names and respective ages from a notepad file.
    I have been able to implement the names and ages into array, and sort the names, but not the ages if there is a plural of the name and put a comma in between.
    Please can you help me - my code is below.
    import java.io.*;
    import java.util.*;
    public class MultipleKeySorting {
        public static void main(String[] args) throws IOException {
            FileInputStream in = new FileInputStream("names_Age.txt");
            BufferedReader br = new BufferedReader(new InputStreamReader(in));
            int maxIndx = -1;
            String a[] = new String[12];
            for (int h = 0; h < a.length-1; h++) {
                maxIndx++;
                a[maxIndx] = br.readLine();
                System.out.println(a[maxIndx]);
            }
            sort(a);
            System.out.println("");
            print(a);
        }
        static String[] sort(String[] a) {
            String min;
            int minIndex;
            for (int i = 0; i < a.length; ++i) {
                min = a[i];
                minIndex = i;
                for (int j = i + 1; j < a.length-1; j++) { //Find minimum
                    if (min.charAt(0) > a[j].charAt(0)) {
                        min = a[j];
                        minIndex = j;
                    }
                }
                a[minIndex] = a[i]; //swap
                a[i] = min;
            }
            return a;
        } 
        public static void print(String[] a) {
            // prints the elements of the specified array in sequence.
            if (a == null || a.length == 0) return;
            for (int i = 0; i < a.length-1; i++)
                System.out.println(a[i] + ", ");
        }
    }
    Last edited by ComputerSaysNo; January 30th, 2011 at 08:05 AM.


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    Default Re: Selection Sorting a text array

    Without knowing the contents of the file its hard to say what is going on.

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    Default Re: Selection Sorting a text array

    The data in the notepad is:
    Jones 14
    Abrams 15
    Smith 19
    Jones 9
    Alexander 22
    Smith 20
    Smith 17
    Tippurt 42
    Jones 2
    Herkman 12
    Jones 11

    The output should be:
    Abrams, 15
    Alexander, 22
    Herkman, 12
    Jones, 2
    Jones, 9
    Jones, 11
    Jones, 14
    Smith, 17
    Smith, 19
    Smith, 20
    Tippurt, 42

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    Default Re: Selection Sorting a text array

    Check the size of your array versus the number of input lines/names, if the input lines is less than the size of the array the last few elements of the array will never be set (eg their value will be null).

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    Default Re: Selection Sorting a text array

    Thanks, but I think that my array size is fine - it's just that I don't know how to sort the ages out and put the comma in between the name and age of each line.

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    Default Re: Selection Sorting a text array

    Quote Originally Posted by ComputerSaysNo View Post
    Thanks, but I think that my array size is fine - it's just that I don't know how to sort the ages out and put the comma in between the name and age of each line.
    Double check...I only count 11 entries in the file, yet you allocate an array size of 12.

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