Java，异常，最好的方法，考试准备

Question

我正在准备基础编程考试。我现在正在研究异常，但似乎不知道如何最好地使用它。我给你第一个代码，然后是第二个代码，我尝试进行检查异常。任何对此的意见都会让我感激不尽!

无异常(exception):

public boolean uttak(int species, int kroner, int skilling) {
     if (species<=this.species && kroner<=this.kroner && skilling <=this.skilling)
     {
         this.species -=species;
         this.kroner -=kroner;
         this.skilling -=skilling;
         return true;
     }
     else return false;

还有我困惑的异常(exception):

public void uttak(int species, int kroner, int skilling){
    try{
       if (species<=this.species && kroner<=this.kroner && skilling <=this.skilling)
        {
            this.species -=species;
            this.kroner -=kroner;
            this.skilling -=skilling;
        }
    }
    catch (Exception e){
        System.err.println ("Withdrawals can not be done when there is" +
                             " insufficient money in the machine.");
    }

Answer 1

您可能正在寻找这样的东西:

// custom checked exception type
public class WithdrawalException extends Exception {
     public WithdrawalException(String msg) {
         super(msg);
     }
}

public boolean uttak(int species, int kroner, int skilling) throws WithdrawalException { // checked exceptions need to be declared in the throws clause 
     if (species<=this.species && kroner<=this.kroner && skilling <=this.skilling)
     {
         this.species -=species;
         this.kroner -=kroner;
         this.skilling -=skilling;
         return true;
     }
     else
         // throw an exception
         throw new WithdrawalException("Withdrawals can not be done when there is insufficient money in the machine.");
}

并在调用代码中使用它，如下所示

try {
    uttak(i1, i2, i3);
} catch (WithdrawalException ex) {
    System.err.println("Something went wrong. Message: "+ex.getMessage());
}