Java -if else顯示多個輸出

Question

我有這一點的代碼返回到程序的開始，如果沒有預期的答案。

... 
else // returns to start for unsatisfactory 
{ 
    System.out.println(); 
    System.out.println(); 
    System.out.println("Check your spelling and try again"); 
    main (args);          
} 
... 

但是當我輸入不同的字，然後再次通過並進入預期字詞程序輸出兩個不同的結果

---

薪水：加薪$ 100.00

金額：$ 4.00

您的新薪水：$ 104.00


當前工資：$ 100.00

金額給自己加薪的：$ 0.00

你的新的工資：$ 100.00

---

我試圖用一個else if語句可能消除的一個原因，但它造成了同樣的事情。

import java.util.Scanner; 
import java.text.NumberFormat; 

public class Salary { 
    public static void main (String[] args) { 
     double currentSalary; // employee's current salary 
     double raise = 0.0;   // amount of the raise 
     double newSalary;  // new salary for the employee 
     String rating;   // performance rating 

     Scanner scan = new Scanner(System.in); 
     System.out.print ("Enter the current salary: "); 
     currentSalary = scan.nextDouble(); 

     System.out.print ("Enter the performance rating (Excellent, Good, or Poor): "); 

     rating = scan.next(); 

     // Computes raise with if-else 
     if ((rating.equals("Excellent")) || (rating.equals("excellent"))) { 
      // calculates raise for excellent 
      raise = .06 * currentSalary; 
     } 
     else if ((rating.equals("Good")) || (rating.equals("good"))) { 
      // calculates raise for good 
      raise = .04 * currentSalary; 
     } 
     else if ((rating.equals("Poor")) || (rating.equals("poor"))) { 
      // calculates raise for poor 
      raise = .015 * currentSalary; 
     } 
     else { 
      // returns to start for unsatisfactory 
      System.out.println(); 
      System.out.println(); 
      System.out.println("Check your spelling and try again"); 
      main (args); 
     }  

     newSalary = currentSalary + raise; 

     // Print the results 

     NumberFormat money = NumberFormat.getCurrencyInstance(); 
     System.out.println(); 
     System.out.println("Current Salary:  " + money.format(currentSalary)); 
     System.out.println("Amount of your raise: " + money.format(raise)); 
     System.out.println("Your new salary:  " + money.format(newSalary)); 
     System.out.println(); 
    } 
} 

Answer 1

那（第二）調用您對main()「完成」，回來了到由啓動程序調用的「第一」之一。

因此，第一批結果來自您明確致電main()。第二批來自何時該通話結束，您又回到您打電話的地方。

不推薦調用main()遞歸。你應該在main（）中使用while循環。即保持要求輸入，直到你知道輸入有效，然後實際使用它。

Answer 2

在您致電main (args);之後，您不會回來，因此程序的每一次迭代都將繼續。

你應該後main (args);

{ 
     System.out.println(); 
     System.out.println(); 
     System.out.println("Check your spelling and try again"); 
     main (args); 
     return; 

} 

編輯添加return;：由John3136指出你不應該叫main (args)遞歸無論是。

Answer 3

那是因爲當你沒有得到預期的輸入時，遞歸地調用main（這不被認爲是好的練習）。輸入（第二次）預期輸入後，必須仍然執行初始main的剩餘部分，然後輸入0.026作爲輸入無效時使用raise。

您的問題的實用解決方案可能會避免遞歸調用main幷包裹例如在一個循環中輸入驗證像這樣

... 
System.out.print ("Enter the performance rating (Excellent, Good, or Poor): "); 
while (true) { 
    rating = scan.next(); 
    if ((rating.equals("Excellent")) || (rating.equals("excellent"))) 
    { 
     raise = .06 * currentSalary; break; 
    } 
    else if ((rating.equals("Good")) || (rating.equals("good"))) 
    { 
     raise = .04 * currentSalary; break; 
    } 
    else if ((rating.equals("Poor")) || (rating.equals("poor"))) 
    { 
     raise = .015 * currentSalary; break; 
    } 
    else 
    { 
     System.out.println(); 
     System.out.println(); 
     System.out.println("Check your spelling and try again");  
    } 
} 
... 

Answer 4

你不應該叫主recursively.you應該使用do while循環，因爲我更新的代碼和它的正常工作。

import java.util.Scanner; 

    import java.text.NumberFormat; 



    public class Salary { 

    public static void main (String[] args) { 

    double currentSalary; // employee's current salary 

    double raise = 0.0;   // amount of the raise 

    double newSalary;  // new salary for the employee 

    String rating;   // performance rating 

    boolean flag=false; // to check input 


    Scanner scan = new Scanner(System.in); 


do{ 

     System.out.print ("Enter the current salary: "); 

     currentSalary = scan.nextDouble(); 

     System.out.print ("Enter the performance rating (Excellent, Good, or Poor): "); 

     rating = scan.next(); 


     // Computes raise with if-else 
     if ((rating.equals("Excellent")) || (rating.equals("excellent"))) // calculates raise for excellent 
      { 
        raise = .06 * currentSalary; 
        flag=true; 

      } 
      else if ((rating.equals("Good")) || (rating.equals("good"))) // calculates raise for good 
       { 
        raise = .04 * currentSalary; 
        flag=true; 

       } 
      else if ((rating.equals("Poor")) || (rating.equals("poor"))) // calculates raise for poor 
       { 
        raise = .015 * currentSalary; 
        flag=true; 

       } 
     else              // returns to start for unsatisfactory 
      { 
        System.out.println(); 
        System.out.println(); 
        System.out.println("Check your spelling and try again"); 
        flag=false; 

      }  

}while(!flag); 


    newSalary = currentSalary + raise; 



    // Print the results 

    NumberFormat money = NumberFormat.getCurrencyInstance(); 

    System.out.println(); 

    System.out.println("Current Salary:  " + money.format(currentSalary)); 

    System.out.println("Amount of your raise: " + money.format(raise)); 

    System.out.println("Your new salary:  " + money.format(newSalary)); 

    System.out.println(); 






     } 

    } 

Answer 5

您可能想要考慮另一種方法。如果輸入無效或嘗試修復，請終止該問題。下面的例子是「修復」的做法，

public class Salary { 
    public static void main(String[] args) { 
     IPM ipm; 
     if (verify(args)) { 
      ipm = new IPM(args); 
     } else { 
      Scanner scan = new Scanner(System.in); 
      String[] update; 
      do { 
       update = repair(scan); 
      } while (!verify(update)); // You may want a loop count as well... 
      ipm = new IPM(update); 
     } 
     ipm.print(); 
    } 

    public static boolean verify(String[] s) { 
     return IPM.verify(s); 
    } 

    public static String[] repair (Scanner s) { 
     // Request new input and store it in an array of strings. 
     // This method does not validate the input. 
    } 
} 

public class IPM { 
    double currentSalary; 
    double raise = 0.0; 
    double newSalary; 
    String rating; 

    IPM(String[] input) { 
     // Set attributes of IPM. 
    } 

    public static boolean verify(String[] s) { 
     //Determine if the input is valid. 
    } 

    public void print() { 
     // Print IPM object. 
    } 
} 

注意，從工資調用IPM.verify()。這應該是IPM責任的一部分，因爲Salary不需要知道任何關於main的內容。此外，類IPM可能會更改，並且IPM.verify()的調用將不會要求所有驗證IPM的類都被更改。