Java语法错误缓冲的读取器

Question

I'm writing a class that just reads a text file and prints out the lines. I'm getting an error on the line containing BufferedReader rd = new BufferedReader(new FileReader("file.txt")); saying that Syntax error on token ";", { expected after this token. I've tried placing it within a method, and within a try catch block as it recommends but then I'm unable to resolve the rd variable. I'm using the acm package so some of the other syntax may look different but I receive no other errors. Any help would be greatly appreciated =)

import acm.program.*;
import acm.util.*;
import java.io.*;
import java.util.*;

public class FileReading extends ConsoleProgram {   

BufferedReader rd = new BufferedReader(new FileReader("file.txt"));

try {
    while (true) {          
        String line = rd.readLine();
        if (line == null) {
            break;
        }
        println(line);
    }
    rd.close();
}
catch (IOException ex) {
    throw new ErrorException(ex);
    }
}
}

Answer 1

Code blocks like this should be embodied inside a method or a static clause. Something like:

public class FileReading extends ConsoleProgram {   

   public void readFile(){
     BufferedReader rd = null;
     try {
         rd = new BufferedReader(new FileReader("file.txt"));
         while (true) {          
            String line = rd.readLine();
            if (line == null) {
                break;
            }
            println(line);
         }
     }catch (IOException ex) {
         throw new ErrorException(ex);
     }finally{
        try{
         rd.close();
        }catch (IOException ex) {
         throw new ErrorException(ex);
        }
     }
   }
}

Answer 2

As answered by others, you cant provide your code in the general part of the class, it has to be within a method or static block.

By putting the code block in the constructor the problem went away. See below for example.

import acm.program.*;
import acm.util.*;
import java.io.*;
import java.util.*;

public class FileReading extends ConsoleProgram {   
public FileReading()
{
BufferedReader rd = new BufferedReader(new FileReader("file.txt"));

try {
    while (true) {          
        String line = rd.readLine();
        if (line == null) {
            break;
        }
        println(line);
    }
    rd.close();
}
catch (IOException ex) {
    throw new ErrorException(ex);
    }
}
}
}

Answer 3

Create a method... and inside that do this... Not directly inside the class

eg:

public void go()
{

    BufferedReader rd = new BufferedReader(new FileReader("file.txt"));

try {
    while (true) {          
        String line = rd.readLine();
        if (line == null) {
            break;
        }
        println(line);
    }
    rd.close();
}
catch (IOException ex) {
    throw new ErrorException(ex);
    }
}

}