[英]unable to read file in java
我試圖讓用戶輸入一個整數,基於整數值,我正在調用mix函數以讀取文件內容,如下代碼所示。 我得到這個錯誤:
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"));
^
有什么想法,我在這里可能做錯了什么?
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();
}
}
}
錯誤表現力強。
urlScan
局部變量 (局部變量沒有默認值) fileScan = new Scanner (new File("input.txt"));
在try/catch
周圍。 或聲明您的方法可能在方法簽名中引發FileNotFoundException。 (新的File(str)可能會拋出FileNotFoundException
,這是一個已檢查的異常 ,編譯器將強制您對其進行處理)。 首先, urlScan
未初始化。
其次,您應該將fileScan = new Scanner (new File("input.txt"));
嘗試/捕獲FileNotFoundException
。
局部變量必須在使用前進行初始化,因此請取消注釋此行:
urlScan = new Scanner (url);
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