java - 我需要提供单独的异常语句。1. 空字符串和 2. 有效数字数据

Question

try{
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
            System.out.println(" Enter the Amount of articles to be ordered.");
            amount = reader.readLine();

            if(amount.trim().isEmpty()){
                System.out.println("Amount Entered is Empty");
            }

            for(int count=0;count<amount.length();count++){
                if(!Character.isDigit(amount.charAt(count))){
                    throw new NumberFormatException();
                }
            }            
            order.validateAmount(amount);
        }catch(NumberFormatException numbere){
            System.out.println("Either Number format is uncorrect or String is Empty, Try Again.");
    }

上面的代码为空字符串异常和无效数字数据异常提供了一个 println() 语句，这是我不想要的。我想要两个异常的单独 println() 语句。怎么获得？

Answer 1

1. 您可以使用两个不同的例外，例如NumberFormatExceptionandIllegalArgumentException并执行两个不同catch的子句。

       ...
       if (amount.isEmpty())
           throw new IllegalArgumentException();
       ...
   
   } catch (NumberFormatException numbere) {
       System.out.println("Either Number format is uncorrect, Try Again.");
   } catch (IllegalArgumentException empty) {
       System.out.println("String is empty, Try Again.");
   }
   

2. 使用相同的异常，但消息不同：

   try {
       BufferedReader reader = new BufferedReader(new InputStreamReader(
               System.in));
       System.out.println(" Enter the Amount of articles to be ordered.");
       String amount = reader.readLine();
   
       if (amount.trim().isEmpty()) {
           System.out.println("Amount Entered is Empty");
       }
   
       if (amount.isEmpty())
           throw new IllegalArgumentException("String is empty.");
   
   
       for (int count = 0; count < amount.length(); count++)
           if (!Character.isDigit(amount.charAt(count)))
               throw new IllegalArgumentException("Number format incorrect.");
   
       order.validateAmount(amount);
   } catch (IllegalArgumentException e) {
       System.out.println(e.getMessage() + " Try again.");
   }
   

3. 或者，您可以使用两个不同的构造函数来创建自己Exception的构造函数，并使用一个标志来说明异常是由于错误的数字还是空字符串造成的。

Answer 2

由于空字符串是“预期”异常，因此我不会使用异常但会检查它：

if ( amount.trim().equals( string.empty) )
{
   System.out.println("string empty" );
}
else
{
   //do your other processing here
}

另一个检查空虚将是amount.trim().length == 0

如果你真的想使用异常：

if( amount.trim().equals( string.empty) )
{
   throw new IllegalArgumentException( "Amount is not given" );
}

并添加另一个 catch()

}
catch( NumberFormatException numbere)
{
}
catch( IllegalArgumentException x )
{
  // Amount not given
}