Java 中的“找不到符号 - 方法 hasNextLine()”错误

Question

I am trying to write a program that uses file I/O to score personality tests. However, when I get to this code:

while (f.hasNextLine()) {

I get the error described in the title. Here is the code in its entirety. I import all of the necessary I/O and utilities prior and I think I am declaring the file variable correctly. I know that this method exists, but what is the problem?

import java.io.*;
import java.util.*;
public class PersonalityTest {
    public static Scanner input = new Scanner(System.in);

    public static void main(String[] args) throws IOException {
        String input = input();
        String output = output();
        results(input, output);
        System.out.println("Your results are located in the file you requested.");
    }

    public static String input() throws IOException {
        System.out.print("Input file name: ");
        String file = input.nextLine();
        File f = new File(file);
        System.out.println();

        while (!f.exists()) {
            System.out.print("File not found. Try again: ");
            file = input.nextLine();
            f = new File(file);
            System.out.println();
        }

        return file;
    }

    public static String output() {
        System.out.print("Output file name: ");
        String output = input.nextLine();
        return output;
    }

    public static void results(String input, String output) throws IOException {
        PrintStream write = new PrintStream(new File(output));
        File f = new File(input);

        while (f.hasNextLine()) {
            String name = f.nextLine();
            String type = "ESTJ";
            String answers = f.nextLine();
            char[] choices = new char[70];

            for (int i = 0; i <= 69; i++) {
                choices[i] = answers.charAt(i);
            }

            int aCount = 0;
            int bCount = 0;

            for (int i = 0; i <= 69; i+=7) {
                if (choices[i].toLowerCase == 'a') {
                    aCount+=1;
                }
                if (choices[i].toLowerCase == 'b') {
                    bCount+=1;
                }
            }

            int pct1 = (int)Math.round((bCount/(aCount+bCount))*100);

            if (pct1 > 50) {
                type.replace('E','I');
            }
            if (pct1 == 50) {
                type.replace('E','X');
            }

            int aCount2 = 0;
            int bCount2 = 0;

            for (int i = 2; i <= 69; i+=7) {
                if (choices[i].toLowerCase == 'a') {
                    aCount2+=1;
                }
                if (choices[i].toLowerCase == 'b') {
                    bCount2+=1;
                }
                if (choices[i+1].toLowerCase == 'a') {
                    aCount2+=1;
                }
                if (choices[i+1].toLowerCase == 'b') {
                    bCount2+=1;
                }
            }

            int pct2 = (int)Math.round((bCount2/(aCount2+bCount2))*100);

            if (pct2 > 50) {
                type.replace('S','N');
            }
            if (pct2 == 50) {
                type.replace('S','X');
            }

            int aCount3 = 0;
            int bCount3 = 0;

            for (int i = 4; i <= 69; i+=7) {
                if (choices[i].toLowerCase == 'a') {
                    aCount3+=1;
                }
                if (choices[i].toLowerCase == 'b') {
                    bCount3+=1;
                }
                if (choices[i+1].toLowerCase == 'a') {
                    aCount3+=1;
                }
                if (choices[i+1].toLowerCase == 'b') {
                    bCount3+=1;
                }
            }

            int pct3 = (int)Math.round((bCount3/(aCount3+bCount3))*100);

            if (pct3 > 50) {
                type.replace('T','F');
            }
            if (pct3 == 50) {
                type.replace('T','X');
            }

            int aCount4 = 0;
            int bCount4 = 0;

            for (int i = 6; i <= 69; i+=7) {
                if (choices[i].toLowerCase == 'a') {
                    aCount4+=1;
                }
                if (choices[i].toLowerCase == 'b') {
                    bCount4+=1;
                }
                if (choices[i+1].toLowerCase == 'a') {
                    aCount4+=1;
                }
                if (choices[i+1].toLowerCase == 'b') {
                    bCount4+=1;
                }
            }

            int pct4 = (int)Math.round((bCount4/(aCount4+bCount4))*100);

            if (pct4 > 50) {
                type.replace('J','P');
            }
            if (pct4 == 50) {
                type.replace('J','X');
            }

            write.println(name + ": [" + pct1 + ", " + pct2 + ", " + pct3 + ", " + pct4 + "] = " + type);

            write.close();
        }
    }
}

Answer 1

java.io.File does not have a hasNextLine() method. That's a method that exists in java.util.Scanner . Scanner has a constructor that takes a File object as an argument and allows it to use the specified file for input - you should probably try using that one:

Scanner s = new Scanner(new File(input));

EDIT:

That said, Scanner can be a bit of a performance killer (a bit?). It is often faster to use a BufferedReader and its readLine() method to read a single line into a String object and then parse the String manually. You can get a BufferedReader from a File with a bit of trickery:

BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream(file)));

Answer 2

instead of using hasNextLine() method, which is non-existent in a File object, an alternative would be to access your file using an inputstream class like FileInputStream and wrapped inside a decorator class like BufferedReader , which would allow you to read its contents per line, using readLine() method....