我試圖讓這個工作，但它顯示errro在fileReader語句

Question

這是主要類，它適用於第一步當我輸入1或2爲下一步它會給出錯誤說「錯誤讀取文件

公共靜態無效的主要（字串[] args）拋出IOException異常{

Scanner sc = new Scanner(System.in); 
    System.out.println("1.Fraction Calculator"); 
    System.out.println("2.Grading Scheme"); 
    System.out.println("Enter Your Choice:"); 
    int ip = sc.nextInt(); 
    String frac1, frac2; 
      // creating an object of Fraction class 
    Grading grad=new Grading(); 
    grad.readFile(); 
    grad.calculateAverage(); 
    grad.calculateTestAvg(); 
    // creating an object of Fraction class 
    Fraction frac =new Fraction(); 


    switch(ip){ 
     case 1: System.out.println("Enter two fractions:"); 
       // input of the two fractions 
       frac1 = sc.next(); frac2 = sc.next(); 
       // displaying the result table 
       System.out.println("Addition: " + frac.add(frac1, frac2) + "\nSubtraction: " + frac.sub(frac1,frac2) + "\nMultiplication: " + frac.mul(frac1,frac2) + "\nDivision: " + frac.div(frac1, frac2)); 
       break; 

     case 2: grad.printGrades(); break; 

     default : break; 
    } 
} 

Answer 1

因爲你沒有處理java.io.FileNotFoundException，則 可以拋出異常或使用try catch塊來處理它

t hrows例外

void Grading()throws FileNotFoundException{ 
    FileReader fr = new FileReader("score.txt"); 
    BufferedReader br = new BufferedReader(fr); 
} 

的try-catch

void Grading(){ 

    FileReader fr = null; 
    try { 
     fr = new FileReader("score.txt"); 
    } catch (FileNotFoundException e) { 
     e.printStackTrace(); 
    } 
    BufferedReader br = new BufferedReader(fr); 
} 

Answer 2

你必須throws FileNotFoundException與FileReader所以你有兩個選擇：

void Grading() throws FileNotFoundException { 
    FileReader fr = new FileReader("score.txt"); 
    BufferedReader br = new BufferedReader(fr); 
} 

或者使用try{}catch(){}：

void Grading() { 
    FileReader fr; 
    try { 
     fr = new FileReader("score.txt"); 
    } catch (FileNotFoundException ex) { 
     //... 
    } 
    BufferedReader br = new BufferedReader(fr); 
} 

編輯

不要忘了導入這個庫：

import java.io.BufferedReader; 
import java.io.FileNotFoundException; 
import java.io.FileReader;