当从控制台读取不同类型的数字时，减少重复代码

Question

我已经创建了三个方法readLong，readInt和readDouble，它们基本上做了同样的事情。唯一不同的是扫描仪调用的方法。如何通过将所有代码全部转换为一种方法来减少重复代码？

public long readLong(String description) 
    { 
     System.out.println(description); 
     long nrToReturn = 0; 
     boolean acceptedValue = false; 

     do { 
      System.out.println(); 
      System.out.print("Choose one: "); 
      try 
      { 
       nrToReturn = consoleScanner.nextLong(); //Only line thats different except return value 
       acceptedValue = true; 
      }catch(Exception e) 
      { 
       acceptedValue = false; 
       consoleScanner.nextLine(); 
      } 
     }while (!acceptedValue); 

     consoleScanner.nextLine(); 
     return nrToReturn; 
    } 

Answer 1

在这里，我们一起去一个想法：

import java.util.Scanner; 

public class ScannerTest { 

    private Scanner consoleScanner; 

    public ScannerTest() { 
     consoleScanner = new Scanner(System.in); 
    } 

    @SuppressWarnings("unchecked")  
    private <T extends Number> T readType(String description, Class<T> desiredType) { 
     System.out.println(description); 
     Number result = null; 

     while (result == null) { 
      System.out.println(); 
      System.out.print("Choose one: "); 
      try { 
       if (Integer.class.equals(desiredType)) { 
        result = new Integer(consoleScanner.nextInt()); 
       } else if (Long.class.equals(desiredType)) { 
        result = new Long(consoleScanner.nextLong()); 
       } 
      } catch(Exception e) { 
       consoleScanner.nextLine(); 
      } 
     } 

     consoleScanner.nextLine(); 
     return (T) result; 
    } 

    public long readLong(String description) { 
     return this.readType(description, Long.class); 
    } 

    public int readInt(String description) { 
     return this.readType(description, Integer.class); 
    } 

    public static void main(String[] args) { 
     ScannerTest t = new ScannerTest(); 
     t.readLong("Reading a long value..."); 
     t.readInt("Reading an integer value..."); 
    } 
} 

更新，以下@ Michu93想法单一透明的方法：

import java.util.Scanner; 

public class ScannerTest { 

    private Scanner consoleScanner; 

    public ScannerTest() { 
     consoleScanner = new Scanner(System.in); 
    } 

    @SuppressWarnings("unchecked") 
    public <T extends Number> T readNumber(String description) { 
     System.out.println(description); 
     Number result = null; 

     while (result == null) { 
      System.out.print("\nChoose one: "); 
      String textRead = consoleScanner.next(); 

      try { 
       result = new Integer(textRead); 
      } catch(Exception e1) { 
       try { 
        result = new Long(textRead); 
       } catch (Exception e2) { 
        try { 
         result = new Double(textRead); 
        } catch (Exception e3) { 
        } 
       } 
      } 
      consoleScanner.nextLine(); 
     } 

     return (T) result; 
    } 

    public static void main(String[] args) { 
     ScannerTest t = new ScannerTest(); 
     for (int i = 0; i < 3; i++) { 
      Number input = t.readNumber(i + ": Reading int, long or double..."); 
      System.out.println("Input class: " + input.getClass().getCanonicalName()); 
      System.out.println("Input value: " + input); 
     } 
    } 
}