使用Scanner读取文件：为什么在使用Scanner读取java文件时出现错误？

This example demonstrates using Scanner to read a file line by line (it does not perform a write operation) I don't know why I get an error when I try to compile. Could somebody explain the reason to me?. I'm using jcreatorLE and JDK 1.6 to run my program:

此示例演示如何使用Scanner逐行读取文件(它不执行写入操作)我不知道为什么在尝试编译时出现错误。有人可以向我解释一下原因吗?我正在使用jcreatorLE和JDK 1.6来运行我的程序:

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

public final class File_read {

  public static void main(String... aArgs) throws FileNotFoundException {
    ReadWithScanner parser = new ReadWithScanner("C:\\Temp\\test.txt");
    parser.processLineByLine();
    log("Done.");
  }

  /**
  * @param aFileName full name of an existing, readable file.
  */
  public ReadWithScanner(String aFileName){
    fFile = new File(aFileName);  
  }

  /** Template method that calls {@link #processLine(String)}.  */
  public final void processLineByLine() throws FileNotFoundException {
    Scanner scanner = new Scanner(fFile);
    try {
      //first use a Scanner to get each line
      while ( scanner.hasNextLine() ){
        processLine( scanner.nextLine() );
      }
    }
    finally {
      //ensure the underlying stream is always closed
      scanner.close();
    }
  }

  /** 
  * Overridable method for processing lines in different ways.
  *  
  * <P>This simple default implementation expects simple name-value pairs, separated by an 
  * '=' sign. Examples of valid input : 
  * <tt>height = 167cm</tt>
  * <tt>mass =  65kg</tt>
  * <tt>disposition =  "grumpy"</tt>
  * <tt>this is the name = this is the value</tt>
  */
  protected void processLine(String aLine){
    //use a second Scanner to parse the content of each line 
    Scanner scanner = new Scanner(aLine);
    scanner.useDelimiter("=");
    if ( scanner.hasNext() ){
      String name = scanner.next();
      String value = scanner.next();
      log("Name is : " + quote(name.trim()) + ", and Value is : " + quote(value.trim()) );
    }
    else {
      log("Empty or invalid line. Unable to process.");
    }
    //(no need for finally here, since String is source)
    scanner.close();
  }

  // PRIVATE //
  private final File fFile;

  private static void log(Object aObject){
    System.out.println(String.valueOf(aObject));
  }

  private String quote(String aText){
    String QUOTE = "'";
    return QUOTE + aText + QUOTE;
  }
}

This is the result from running it:

这是运行它的结果:

--------------------Configuration: <Default>--------------------
C:\Users\administrador\Documents\File_read.java:15: invalid method declaration; return type required
  public ReadWithScanner(String aFileName){
         ^
1 error

Process completed.

4 个解决方案

#1

When you lifted that code from here :-), you renamed the class but not the constructor. Only constructors are allowed to not have return types.

当你从这里解除代码:-)时,你重命名了类而不是构造函数。只允许构造函数不具有返回类型。

I suggest you either rename the class back or rename the constructor.

我建议您重命名该类或重命名构造函数。

I hope this isn't homework. As it stands, your educator would have an easy time proving plagiarism. You'll need to at least change the variable names as well as class names, you might want to also reformat it a bit including changing the order of methods in the class.

我希望这不是功课。就目前而言,您的教育工作者将有一个轻松的时间来证明抄袭。您至少需要更改变量名称和类名称,您可能还需要重新格式化它,包括更改类中方法的顺序。

That's if it's homework. Which it's not, right? :-)

那就是它的功课。它不是,对吧? :-)

#2

Your "ReadWithScanner" constructor needs to match the name of the class ("File_read")

您的“ReadWithScanner”构造函数需要匹配类的名称(“File_read”)

public File_read(String aFileName){
    fFile = new File(aFileName);  
}

#3

Your class is named File_read and your constructor is named ReadWithScanner. The warning is that your constructor needs to be named the same as the class.

您的类名为File_read,您的构造函数名为ReadWithScanner。警告是您的构造函数需要与类命名相同。

#4

The name of the class is File_read, so the constructor name should be File_read but you gave the name as ReadWithScanner that is why its complaining. Compiler thinking its a method name so expecting a return type.

该类的名称是File_read,因此构造函数名称应该是File_read,但是您将名称命名为ReadWithScanner,这就是它抱怨的原因。编译器认为它是一个方法名称,因此期望返回类型。

#1