使用Java中的Scanner类从文件读取

Question

I'm trying to read from a file and pass the output as tokens to a HashMap object. Seems like my program cant seem to find the file. Here's the code.

public static void main(String[] args) {


        try {
            HashMap<String, Integer> map = sortingFromAFile("file.rtf");
            System.out.println(map);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
    }

    public static HashMap sortingFromAFile(String fileName) throws FileNotFoundException {

        HashMap<String, Integer> map = new HashMap<String, Integer>();

        Integer count = 1;

        File file = new File(fileName);

        Scanner sc = null;
        try {
            sc = new Scanner(file);
            while(sc.hasNextLine()){
                if (map.containsKey(sc.nextLine())){
                    count+= map.get(sc.nextLine());
                }
                map.put(sc.nextLine(), count);

            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }


        return map;
    }

The file that I'm trying to read is in the root of the project directory.

Here's the error.

Exception in thread "main" java.util.NoSuchElementException: No line found
    at java.util.Scanner.nextLine(Scanner.java:1540)
    at com.soumasish.Main.sortingFromAFile(Main.java:38)
    at com.soumasish.Main.main(Main.java:16)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:134)

Any help please.

Answer 1

Each time you call sc.nextLine() you read another line. So on the first iteration through the loop, if(map.containsKey(sc.nextLine())) reads the first line, and checks whether it's in the map. count += map.get(sc.nextLine()) reads the second line, gets that value from the map and adds it to the count. map.put(sc.nextLine(), count) reads the third line and stores the count there. If there are more than three lines, the loop then runs again, and reads the 4th/5th/6th lines.

You need to use a variable to store the current line, since you can only read each line once:

        while(sc.hasNextLine()){
            String line = sc.nextLine();
            if (map.containsKey(line)){
                count+= map.get(line);
            }
            map.put(line, count);

        }