Java阵列未打印（正在使用BlueJ）

Question

I am currently trying to complete a task for college that requires using java programming. The task goes as follows.

I have to sort through an input file for a "fishing competition". The file firstly gives an integer (between 1-7), then a real number, for each line. The tricky part is that the numbers are not already added up, or in order. This means I have to make the program read the integer, prove its needed location, then add the following weight to that location.

Here's an idea of what the file looks like

3 36.2

6 27.8

7 10.3

I have the general idea on how to complete the whole task, but I am getting stuck on one part, which is printing the total weight for each competitor.

Here is the code that I have written so far. If you could tell me what may be giving me problems, it would be much appreciated. (It is not giving an error code, rather, BlueJ, the software i am using, just continuously tries to run the program)

 import java.io.*; import java.util.Scanner; public class Project7 { public static void main(String[] args) throws FileNotFoundException { Scanner inF = new Scanner(new File("inputpro7.txt")); int [] arrayNum = new int[7]; double [] arrayWeight = new double[7]; int place = inF.nextInt(); double weight = inF.nextDouble(); for (int m = 0; m < 7; m++) { arrayNum[m] = m + 1; } while (inF.hasNextLine()) { if (place == 1) arrayWeight[0] += weight; else if (place == 2) arrayWeight[1] += weight; else if (place == 3) arrayWeight[2] += weight; else if (place == 4) arrayWeight[3] += weight; else if (place == 5) arrayWeight[4] += weight; else if (place == 6) arrayWeight[5] += weight; else arrayWeight[6] += weight; } for (int k = 0; k < 7; k++) System.out.printf("%6d %6.2f%n", arrayNum[k], arrayWeight[k]); inF.close(); } } 

Answer 1

The problem in your code is in While loop. You are continuously reading the first line of the Input file. There is no read nextline statement inside While loop. Even when you put that statement (reading next line) you need some modification in your code. Following is the modified code.

public class ExampleCode {

    public static void main(String[] args) throws FileNotFoundException {
        Scanner inF = new Scanner(new File("Input.txt"));
        int[] arrayNum = new int[7];
        double[] arrayWeight = new double[7];
        int place;
        double weight;

        for (int m = 0; m < 7; m++) {
            arrayNum[m] = m + 1;
        }

        while (inF.hasNextLine()) {
            place = inF.nextInt();
            weight = inF.nextDouble();
            if (place == 1)
                arrayWeight[0] += weight;
            else if (place == 2)
                arrayWeight[1] += weight;
            else if (place == 3)
                arrayWeight[2] += weight;
            else if (place == 4)
                arrayWeight[3] += weight;
            else if (place == 5)
                arrayWeight[4] += weight;
            else if (place == 6)
                arrayWeight[5] += weight;
            else
                arrayWeight[6] += weight;
        }
        for (int k = 0; k < 7; k++)
            System.out.printf("%6d %6.2f%n", arrayNum[k], arrayWeight[k]);
        inF.close();
    }
}

Best way to solve such problem "Process Input file and aggregate the input based on similar Key values" is to use HashMap. Following is the possible solution.

    import java.io.File;
    import java.io.FileNotFoundException;
    import java.util.HashMap;
    import java.util.Map;
    import java.util.Map.Entry;
    import java.util.Scanner;

    public class ExampleCode {

        public static void main(String[] args) throws FileNotFoundException
        {
            Scanner inF = new Scanner(new File("Input.txt"));
            Map<String, Double> table = new HashMap<String, Double>(); 
            String line = "";
            String token[] = new String[2];

            //Process till end of file
            while (inF.hasNextLine())
            {
                //Read each lines
                line = inF.nextLine();
                //Split line based on separator i.e " " character
                //use these tokens as Key-Value pairs
                token = line.split(" ");

                //If table already has the entry add the value to same key entry
                if(table.containsKey(token[0])){
                    Double value = table.get(token[0]) + new Double(token[1]);
                    table.put(token[0], value);
                } else { //If key not found, insert the new entry
                    table.put(token[0], new Double(token[1]));
                }
            }

            for(Entry entry : table.entrySet()){
                System.out.println("Key:"+entry.getKey()+" == Value:"+entry.getValue());
            }
            //close the file 
            inF.close();
        }
    }

Sample Input file: 
2 9.25
4 8.5
1 1.5
2 4.215
5 1.4555
6 8.989
7 1
4 8.049
1 3.567

Output : 
Key:1 == Value:5.067
Key:2 == Value:13.465
Key:4 == Value:16.549
Key:5 == Value:1.4555
Key:6 == Value:8.989
Key:7 == Value:1.0