Question

我正在尝试创建一个程序，要求输入和输出文件名，但是我在制作程序时遇到了麻烦，特别是在询问输出文件的文件名时。这两种方法都会要求用户输入相应的文件名并将该名称作为String返回。这些方法将从main方法调用。它们将返回一个String，因此在调用方法之前应该声明两个String变量。

这是读取输入文件并创建输出文件的零件程序，但是我在添加要求文件名的程序部分时遇到问题。

import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.text.DecimalFormat;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

public class WebberProject3 {
private static Map<String, Integer> ticketTypeToPrice = new HashMap<String, Integer>();
private static final String SPACE = " ";
private static final String CURRENCY_SYMBOL = " $";

    public static void main(String[] args) {
    Scanner scanner = null;
    PrintWriter outputFile = null;
    DecimalFormat decimalFormat = new DecimalFormat();
    decimalFormat.setMinimumFractionDigits(2);
    try {
        File file = new File("portlandvip2.txt");
        scanner = new Scanner(file);
        outputFile = new PrintWriter("portland2out.txt");
        while (scanner.hasNext()) {
            String line = scanner.nextLine();
            String[] entriesOnLine = line.split(" ");
            // Line with price and ticket type
            if(entriesOnLine.length == 2) {
                ticketTypeToPrice.put(entriesOnLine[0],         Integer.parseInt(entriesOnLine[1]));
                StringBuilder sb = new StringBuilder();
                sb.append(entriesOnLine[0])
                    .append(CURRENCY_SYMBOL)
                    .append(decimalFormat.format(Integer.parseInt(entriesOnLine[1])));
                outputFile.println(sb.toString());
            } else if (entriesOnLine.length == 4) {
                //Line with First Name, Last Name, number of Tickets and Price
                int numberOfTickest = Integer.parseInt(entriesOnLine[2]);
                int ticketPrice = ticketTypeToPrice.get(entriesOnLine[3]);
                int totalPrice = numberOfTickest*ticketPrice;
                StringBuilder sb = new StringBuilder();
                sb.append(entriesOnLine[0])
                    .append(SPACE)
                    .append(entriesOnLine[1])
                    .append(CURRENCY_SYMBOL)
                    .append(decimalFormat.format(totalPrice));
                outputFile.println(sb.toString());
            }
        }
    } catch (IOException e) {
        System.out.println("exception:" + e);
    } finally {
        scanner.close();
        outputFile.close();
    }
}
}

为了让这个程序工作，我需要使用标题名称制作两种不同的方法：

public static String getInputFileName()
public static String getOutputFileName()

请帮助，我是编程的初学者，我尝试了一些不同的东西，但没有什么是真的有效。任何帮助将非常感激

这将是我尝试过的一个例子（我在阅读了这篇文章的评论后试过这个）：

import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.text.DecimalFormat;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;


public static void String getInputFileName()
{
  System.out.println("Enter filename here : ");

   String sWhatever;

   Scanner scanIn = new Scanner(System.in);
   sWhatever = scanIn.nextLine();

   scanIn.close();            
   System.out.println(sWhatever);
}
}

public class WebberProject3Test1
{
public static void main(String[] args) {
{
private static Map<String, Integer> ticketTypeToPrice = new HashMap<String, Integer>();
private static final String SPACE = " ";
private static final String CURRENCY_SYMBOL = " $";

public static void main(String[] args) {
    Scanner scanner = null;
    PrintWriter outputFile = null;
    DecimalFormat decimalFormat = new DecimalFormat();
    decimalFormat.setMinimumFractionDigits(2);
    try {
        File file = new File("portlandvip2.txt");
        scanner = new Scanner(file);
        outputFile = new PrintWriter("portland2out.txt");
        while (scanner.hasNext()) {
            String line = scanner.nextLine();
            String[] entriesOnLine = line.split(" ");
            // Line with price and ticket type
            if(entriesOnLine.length == 2) {
                ticketTypeToPrice.put(entriesOnLine[0],    Integer.parseInt(entriesOnLine[1]));
                StringBuilder sb = new StringBuilder();
                sb.append(entriesOnLine[0])
                    .append(CURRENCY_SYMBOL)
                    .append(decimalFormat.format(Integer.parseInt(entriesOnLine[1])));
                outputFile.println(sb.toString());
            } else if (entriesOnLine.length == 4) {
                //Line with First Name, Last Name, number of Tickets and Price
                int numberOfTickest = Integer.parseInt(entriesOnLine[2]);
                int ticketPrice = ticketTypeToPrice.get(entriesOnLine[3]);
                int totalPrice = numberOfTickest*ticketPrice;
                StringBuilder sb = new StringBuilder();
                sb.append(entriesOnLine[0])
                    .append(SPACE)
                    .append(entriesOnLine[1])
                    .append(CURRENCY_SYMBOL)
                    .append(decimalFormat.format(totalPrice));
                outputFile.println(sb.toString());
            }
        }
    } catch (IOException e) {
        System.out.println("exception:" + e);
    } finally {
        scanner.close();
        outputFile.close();
    }
}
}
}

我得到这样的错误：

发现了9个错误：

File: C:\Users\Eddie\CISS100\WebberProject3Test1.java  [line: 10]
Error: Syntax error on tokens, ClassHeader expected instead

File: C:\Users\Eddie\CISS100\WebberProject3Test1.java  [line: 12]
Error: Syntax error on token(s), misplaced construct(s)
File: C:\Users\Eddie\CISS100\WebberProject3Test1.java  [line: 12]
Error: Syntax error on token ""Enter filename here : "", delete this token
File: C:\Users\Eddie\CISS100\WebberProject3Test1.java  [line: 16]
Error: Syntax error on token ";", { expected after this token

File: C:\Users\Eddie\CISS100\WebberProject3Test1.java  [line: 26]
Error: Duplicate method main(java.lang.String[]) in type WebberProject3Test1

File: C:\Users\Eddie\CISS100\WebberProject3Test1.java  [line: 27]
Error: Syntax error, insert "}" to complete BlockStatements

File: C:\Users\Eddie\CISS100\WebberProject3Test1.java  [line: 27]
Error: Syntax error, insert "}" to complete MethodBody

File: C:\Users\Eddie\CISS100\WebberProject3Test1.java  [line: 32]
Error: Duplicate method main(java.lang.String[]) in type WebberProject3Test1

File: C:\Users\Eddie\CISS100\WebberProject3Test1.java  [line: 74]
Error: Syntax error on token "}", delete this token

Answer 1

如果您想要求用户输入，最常见的方法是使用System输入的参数创建Scanner类的实例，如此

Scanner userInput = new Scanner(System.in);

然后，您可以调用此类的方法来获取用户键入的下一行文本，因此您的代码可能看起来像这样

System.out.println("where to read?");
String in = userInput.nextLine();
System.out.println("where to write?");
String out = userInput.nextLine();
Scanner scanner = new Scanner(new File(in));
PrintWriter outputFile = new PrintWriter(out);

此代码允许用户在命令行或netbeans / eclipse中从终端读取和写入。

编译错误：

第10行：public static void String getInputFileName()

必须在类的主体内声明方法/函数。所以移动整个函数

在你的功能之后，你有一个额外的闭合大括号，所以删除它。

您不能两次声明public static void main（String [] args）。您尤其不能在另一个方法中使用方法，因此请删除外部public static void main(String[] args) {和后面的额外开口花括号。

public static void String getInputFileName()只能有一种返回类型，因此请将其设置为void，因为您没有返回。

最后删除末尾关闭大括号的额外内容。

您的代码看起来应该是这样的

import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.text.DecimalFormat;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

public class WebberProject3Test1 {

    private static Map<String, Integer> ticketTypeToPrice = new HashMap<String, Integer>();
    private static final String SPACE = " ";
    private static final String CURRENCY_SYMBOL = " $";

    public static void getInputFileName() {
        System.out.println("Enter filename here : ");

        String sWhatever;

        Scanner scanIn = new Scanner(System.in);
        sWhatever = scanIn.nextLine();

        scanIn.close();
        System.out.println(sWhatever);
    }

    public static void main(String[] args) {
        Scanner scanner = null;
        PrintWriter outputFile = null;
        DecimalFormat decimalFormat = new DecimalFormat();
        decimalFormat.setMinimumFractionDigits(2);
        try {
            File file = new File("portlandvip2.txt");
            scanner = new Scanner(file);
            outputFile = new PrintWriter("portland2out.txt");
            while (scanner.hasNext()) {
                String line = scanner.nextLine();
                String[] entriesOnLine = line.split(" ");
                // Line with price and ticket type
                if (entriesOnLine.length == 2) {
                    ticketTypeToPrice.put(entriesOnLine[0], Integer.parseInt(entriesOnLine[1]));
                    StringBuilder sb = new StringBuilder();
                    sb.append(entriesOnLine[0])
                            .append(CURRENCY_SYMBOL)
                            .append(decimalFormat.format(Integer.parseInt(entriesOnLine[1])));
                    outputFile.println(sb.toString());
                } else if (entriesOnLine.length == 4) {
                    //Line with First Name, Last Name, number of Tickets and Price
                    int numberOfTickest = Integer.parseInt(entriesOnLine[2]);
                    int ticketPrice = ticketTypeToPrice.get(entriesOnLine[3]);
                    int totalPrice = numberOfTickest * ticketPrice;
                    StringBuilder sb = new StringBuilder();
                    sb.append(entriesOnLine[0])
                            .append(SPACE)
                            .append(entriesOnLine[1])
                            .append(CURRENCY_SYMBOL)
                            .append(decimalFormat.format(totalPrice));
                    outputFile.println(sb.toString());
                }
            }
        } catch (IOException e) {
            System.out.println("exception:" + e);
        } finally {
            scanner.close();
            outputFile.close();
        }
    }
}

注意：此代码现在将编译，但这并不意味着我已按照您的意愿执行此操作。

Answer 2

如果您需要阅读用户的输入，您可以这样做：

    System.out.println("Type an input path: ");
    Scanner s = new Scanner (System.in);

    String input = s.nextLine();

在input中，您将获得用户所写的文字。

Answer 3

如果您想要通过在控制台中输入文件名来要求用户提供文件名，您可以使用BufferedReader的readLine或Scanner的nextLine。 BufferedReader的示例：

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class ReadConsoleSystem {
  public static void main(String[] args) {

    System.out.println("Enter filename here : ");

    try{
        BufferedReader bufferRead = new BufferedReader(new InputStreamReader(System.in));
        String s = bufferRead.readLine();

        System.out.println(s);
    }
    catch(IOException e)
    {
        e.printStackTrace();
    }

  }
}

扫描仪示例

import java.util.Scanner;

public class ReadConsoleScanner {
  public static void main(String[] args) {

      System.out.println("Enter filename here : ");

       String sWhatever;

       Scanner scanIn = new Scanner(System.in);
       sWhatever = scanIn.nextLine();

       scanIn.close();            
       System.out.println(sWhatever);
  }
}

取自this article

的示例

如何询问用户输入文件名和输出文件名java？

3 个答案: