Java multidimensional array sorting

I am trying to sort the contents of an array and although it seems to work (no runtime errors, does sorting tasks), the first 10 lines sorted are out of order with the rest of the lines.

class coordSort.java

import java.io.*;
import java.util.Arrays;
import java.util.Scanner;

public class coordSort {
@SuppressWarnings({ "unchecked", "unused" })
public static void main (String args[]) throws IOException {

    String xCoord, yCoord;
    int coordSum;
    Scanner input = new Scanner(System.in);

    //Get x coordinate from user
    System.out.print("Enter x coordinate: ");
    xCoord = input.next();

    //Get x coordinate from user
    System.out.print("Enter y coordinate: ");
    yCoord = input.next();

    boolean sort = false;

    char[] a = xCoord.toCharArray();
    char[] b = yCoord.toCharArray();

    //validate user input is a digit 
    if ( (Character.isDigit(a[0]))  ) {     
        if(Character.isDigit(b[0]) ){
            //digits entered - begin processing all coordinate values
            sort = true;
        }
    }

    //If validation failed, inform user
    if(!sort){
        System.out.println("Please enter a positive numeric value.");
    }

    if(sort){       
        //determine SUM of user entered coordinates
        coordSum = Integer.parseInt(xCoord) + Integer.parseInt(yCoord);

        //define coordinate array
        String[][] coordUnsortedArray = new String[26][3];
        int counter;
        int commaCount;
        String xCoordIn, yCoordIn;
        int intXCoordIn, intYCoordIn, sumCoordIn, coordDiff;

        //define input file
        FileInputStream fileIn = new FileInputStream("coords.txt");
        BufferedReader reader = new BufferedReader(new InputStreamReader(fileIn)); 

        for (int j = 0; j < coordUnsortedArray.length; j++){
            counter = 0;
            commaCount = 0;
            //line from file to variable
            String coordSet = reader.readLine();     

            //look for the second "," to determine end of x coordinate
            for(int k = 0; k < coordSet.length(); k++){
                if (coordSet.charAt(k) == ',') {
                    commaCount++;
                    counter++;
                    if (commaCount == 2){
                        break;
                    }
                }else{
                    counter++;
                }
            }

            //define x coordinate
            xCoordIn = (coordSet.substring(2,(counter - 1)));
            intXCoordIn = Integer.parseInt(xCoordIn);

            //define y coordinate
            yCoordIn = (coordSet.substring((counter),coordSet.length()));
            intYCoordIn = Integer.parseInt(yCoordIn);

            //coordinate calculations
            sumCoordIn = Integer.parseInt(xCoordIn) + Integer.parseInt(yCoordIn);
            coordDiff = sumCoordIn - coordSum;

            //load results to array
            coordUnsortedArray[j][0] = xCoordIn;
            coordUnsortedArray[j][1] = yCoordIn;
            coordUnsortedArray[j][2] = Integer.toString(coordDiff);

            //Output Array (BEFORE SORTING)
            //System.out.println((j + 1) + ") " + coordUnsortedArray[j][0] + " : " + coordUnsortedArray[j][1] + " : " + coordUnsortedArray[j][2]);                  
        }             

        System.out.println("\n");

        fileIn.close();

        String[][] coordsSorted = new String[26][3];

        //Sort array coordDiff, column 3
        Arrays.sort(coordUnsortedArray, new ColumnComparator(2));

        //Print the sorted array
        for(int i = 0; i < coordUnsortedArray.length; i++){
            String[] row = coordUnsortedArray[i];
            System.out.print((i + 1) + ") ");
            for(int j = 0; j < row.length; j++) {
                //System.out.print(row[j] + " | ");
                coordsSorted[i][j] = row[j];
                System.out.print(coordsSorted[i][j] + " : ");
            }
            System.out.print("\n");
        }
    }
}
}

      

class sortCoords.java -

import java.util.Comparator;

@SuppressWarnings("rawtypes")
class ColumnComparator implements Comparator {
    int columnToSort;
    ColumnComparator(int columnToSort) {
        this.columnToSort = columnToSort;
    }
    //overriding compare method
    public int compare(Object o1, Object o2) {
        String[] row1 = (String[]) o1;
        String[] row2 = (String[]) o2;
        //compare the columns to sort
        return row1[columnToSort].compareTo(row2[columnToSort]);
    }

    //overriding compare method
    public int compare1(Object o1, Object o2) {
        String[] row1 = (String[]) o1;
        String[] row2 = (String[]) o2;
        //compare the columns to sort
        return row1[columnToSort].compareTo(row2[columnToSort]);
    }
} 

      

I am trying to sort an array numerically by the third column. The unsorted array is filled with a text file containing something like:

a, 44.67

b, 31.49

s, 93.6

I am performing calculations on an array versus user input and filling the array like this:

44.67,101

31.49.70

93.6.89

I would like sortedArray to output the following:

31.49.70

93.6.89

44.67,101

+3


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3 answers


Possible confusion here:

 return row1[columnToSort].compareTo(row2[columnToSort])

      



This is a string comparison, not a numeric one. If you sort by row, you'll get different results than if you were doing numbers - that is, "1", "10", "100", "9" versus 1,9,10,100

Check out Integer.parseInt and if you can't understand the rest, feel free to ask more questions.

+2


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As stated in the spinning_plate. You need to compare their int values ​​i.e. You need a listing

    int num1 = Integer.parseInt(row1[columnToSort]);
    int num2 = Integer.parseInt(row2[columnToSort]);
    if(num1 > num2)
            return 1;
    else 
            return 0;

      



Put this code in compareTo method and check. Change the return operators to sort in reverse order.

Also, adding some error checking in the method compareTo

will make the code more efficient.

+1


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Ok, so after the help given here, below is the solution we found. Thanks again for helping everyone! Hope the code below helps someone else.

Code for class 1 -

import java.io.*;
import java.util.Arrays;
import java.util.Scanner;

public class coordSort {
    @SuppressWarnings({ "unchecked" })
    public static void main (String args[]) throws IOException {

        String xCoordChar, yCoordChar;
        int xCoord, yCoord, coordSum;
        Scanner input = new Scanner(System.in);

        //Get x coordinate from user
        System.out.print("Enter x coordinate: ");
        xCoordChar = input.next();

        //Get x coordinate from user
        System.out.print("Enter y coordinate: ");
        yCoordChar = input.next();

        boolean sort = false;

        char[] a = xCoordChar.toCharArray();
        char[] b = yCoordChar.toCharArray();

        //validate user input is a digit 
        if ( (Character.isDigit(a[0]))  ) {     
            if(Character.isDigit(b[0]) ){
                //digits entered - begin processing all coordinate values
                sort = true;
            }
        }

        //If validation failed, inform user
        if(!sort){
            System.out.println("Please enter a positive numeric value.");
        }

        if(sort){       
            //Parse user input characters to Integers
            xCoord = Integer.parseInt(xCoordChar);
            yCoord = Integer.parseInt(yCoordChar);

            //determine SUM of user entered coordinates
            coordSum = xCoord + yCoord;

            //define coordinate array
            int[][] coordUnsortedArray = new int[26][3];
            int counter;
            int commaCount;
            String xCoordIn, yCoordIn;
            int intXCoordIn, intYCoordIn, sumCoordIn, coordDiff;

            //define input file
            FileInputStream fileIn = new FileInputStream("coords.txt");
            BufferedReader reader = new BufferedReader(new InputStreamReader    (fileIn)); 

            for (int j = 0; j < coordUnsortedArray.length; j++){
                counter = 0;
                commaCount = 0;
                //line from file to variable
                String coordSet = reader.readLine();     

                //look for the second "," to determine end of x coordinate
                for(int k = 0; k < coordSet.length(); k++){
                    if (coordSet.charAt(k) == ',') {
                        commaCount++;
                        counter++;
                        if (commaCount == 2){
                            break;
                        }
                    }else{
                        counter++;
                    }
                }

                //define x coordinate
                xCoordIn = (coordSet.substring(2,(counter - 1)));
                intXCoordIn = Integer.parseInt(xCoordIn);

                //define y coordinate
                yCoordIn = (coordSet.substring((counter),coordSet.length()));
                intYCoordIn = Integer.parseInt(yCoordIn);

                //coordinate calculations
                sumCoordIn = Integer.parseInt(xCoordIn) + Integer.parseInt    (yCoordIn);
                coordDiff = sumCoordIn - coordSum;

                if (coordDiff < 0){
                    coordDiff = coordDiff * (-1);
                }

                //load results to array
                coordUnsortedArray[j][0] = intXCoordIn;
                coordUnsortedArray[j][1] = intYCoordIn;
                coordUnsortedArray[j][2] = coordDiff;                           
            }             

            fileIn.close();
            System.out.print("\n");
            System.out.println("Array Before Sorting:");
            System.out.println("=====================");

            //Array Before Sorting
            for(int i = 0; i < coordUnsortedArray.length; i++){
                int[] row = coordUnsortedArray[i];
                System.out.print((i + 1) + ") ");
                for(int j = 0; j < (row.length - 1); j++) {
                    coordUnsortedArray[i][j] = row[j];
                    if(j < 1){
                        System.out.print(coordUnsortedArray    [i]    [j] + ",");   
                    }else{
                        System.out.println(coordUnsortedArray    [i]    [j]);
                    }
                }
            }

            System.out.print("\n");
            System.out.print("\n");

            //Sort array coordDiff, column 3
            Arrays.sort(coordUnsortedArray, new ColumnComparator(2));

            System.out.println("Array After Sorting:");
            System.out.println("====================");

            //Original Array After Sorting
            for(int i = 0; i < coordUnsortedArray.length; i++){
                int[] row = coordUnsortedArray[i];
                System.out.print((i + 1) + ") ");
                for(int j = 0; j < (row.length - 1); j++) {
                    coordUnsortedArray[i][j] = row[j];
                    if(j < 1){
                        System.out.print(coordUnsortedArray[i][j] + ",");   
                    }else{
                        System.out.println(coordUnsortedArray    [i]    [j]);
                    }
                }
            }
            }
        }
}

      

Code for class 2 -

import java.util.Comparator;

@SuppressWarnings("rawtypes")
class ColumnComparator implements Comparator {
int columnToSort;
ColumnComparator(int columnToSort) {
this.columnToSort = columnToSort;
}

//Compare method
public int compare(Object o1, Object o2) {
    int[] row1 = (int[]) o1;
    int[] row2 = (int[]) o2;

    int intRow1 = (row1[columnToSort]);
    int intRow2 = (row2[columnToSort]);

    return new Integer(intRow1).compareTo(new Integer(intRow2));
}
}    

      

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