unable to read file in java

Question

I am trying to have user input an interger, based on the integer value, I am calling mix function to read in the file contents as code shows below. I am getting, this error:

Project2.java:43: variable urlScan might not have been initialized
                        while (urlScan.hasNext())
                               ^
Project2.java:34: unreported exception java.io.FileNotFoundException; must be caught or declared to be thrown
                fileScan = new Scanner (new File("input.txt"));
                       ^

Any ideas, what I might be doing wrong here?

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

public class Project2
{
    public static void main(String[] args) 
    {

                System.out.println("Select an item from below: \n");
                System.out.println("(1) Mix");
                System.out.println("(2) Solve");
                System.out.println("(3) Quit");

                int input;
                Scanner scan= new Scanner(System.in);
                input = scan.nextInt();

                System.out.println(input);  
                if(input==1) {
                    mix();
                }
                else{
                    System.out.println("this is exit");
                    } 
        }




        public static void mix()
          {
                String url;
                Scanner fileScan, urlScan;
                fileScan = new Scanner (new File("input.txt"));
                // Read and process each line of the file
                while (fileScan.hasNext())
                    {
                        url = fileScan.nextLine();
                        System.out.println ("URL: " + url);
                        //urlScan = new Scanner (url);
                        //urlScan.useDelimiter("/");
                        //  Print each part of the url
                        while (urlScan.hasNext())
                        System.out.println ("   " + urlScan.next());
                        System.out.println();
                     }
            }
     }

Answer 1

The errors are pretty expressive.

• Initialize your urlScan local variable (local variables don't get default values)
• Wrap the fileScan = new Scanner (new File("input.txt")); around try/catch . or declare that your method might throw FileNotFoundException in your method signature. (new File(str) might throw FileNotFoundException which is a checked exception and compiler will force your handled it).

Answer 2

First, urlScan isn't initialized.

Second, you should surround fileScan = new Scanner (new File("input.txt")); with an try/catch for FileNotFoundException .

Answer 3

局部变量必须在使用前进行初始化，因此请取消注释此行：

urlScan = new Scanner (url);