Java 解决加密程序中的错误，其中/如何在null时声明变量可以'；不可用

我将非常感谢您对我遇到的这个问题的任何帮助。在下面代码的第27行，我得到一个错误，位置无法解析为变量。（BufferedReader br=Parse.parseLocation（位置，键）；） 初始化为null在我的程序中不起作用（我没有得到我想要的结果），我一直在想办法解决这个问题。应在何处以及如何正确申报？ 为了更加清晰，我还粘贴了下面的解析文件。 提前谢谢

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

public class Main {


public static void main(String[] args){
    System.out.println("Enter Cipher Key:");
    Scanner s = new Scanner(System.in);
    String key = s.nextLine();


   System.out.println("Enter a text file or URL to encrypt:");
    System.out.flush();
    Scanner r = new Scanner(System.in);
    String filename = r.nextLine();
    File f = new File(filename);

    r.close();
    s.close();

    try{
    Porta cipher = new Porta(key);

    cipher.ensureCapacity((int)f.length());       
    FileWriter fw = new FileWriter("out.txt");
    BufferedReader br = Parse.parseLocation(location, key);
    String line = null;


       while((line = br.readLine()) != null){
            String encrypted = cipher.encrypt(line.toUpperCase());
            fw.write(encrypted + "\n" );

        }

        br.close();
        fw.flush();
        fw.close();
    }catch(Exception e){
        System.out.println("Yikes! Something nasty happened");
        e.printStackTrace();
    }
}

}

以及上述解析文件，如下所示：

import java.io.*;
import java.net.URL;

public class Parse {

private static BufferedReader br;
private static final String FORM = "http://"; //Identify a URL header   
public static BufferedReader parseLocation(String location, String key) 
{       
    try{
        if(location.startsWith(FORM)){
            URL url = new URL(location);    
            br = new BufferedReader(new InputStreamReader(url.openStream())); 
            System.out.println("\nURL successfully read");
        }

        else{ //If input is a file
            File file = new File(location); //New instance of URL
            if(file.exists()){
                br = new BufferedReader(new InputStreamReader(new FileInputStream(file))); 
            }
            System.out.println("\nFile successfully read");
        }
    }

    catch(IOException e)
    {
        e.printStackTrace(); //Prints the stack trace of the Exception to System.err.
    }

    return br; 
    }

}

这里您将

location

作为参数传递，但尚未声明

location

变量

在调用

Parse.parseLocation（…）

之前，需要将其声明为全局变量或局部变量。像这样的

String location = "http://http://stackoverflow.com";
BufferedReader br = Parse.parseLocation(location, key);

String location = "http://http://stackoverflow.com";
BufferedReader br = Parse.parseLocation(location, key);