Question

I have this code.

 class NumberMachine { 
   public static void main(String [] args) { 
     Integer wi1 = new Integer("420"); 
     int i = 101; 
     Integer wi2 = i*420/101; 

     if(wi1 == wi2)
       System.out.print(" =="); 
     if(wi1.equals(wi2))
       System.out.print(" equal"); 
     float f = 1.23f; 
     new NumberMachine().printIt(f); 
  } 

  void printIt(Float f) { 
    System.out.println(" Float"); 
  } 

  void printIt(double d) { 
    System.out.println(" double"); 
  } 
} 

Why result is “equal double” but no “equal Float” ?

Answer 1

To determine which method should be called, the compiler goes through the following list, as detailed in the JLS #5.3 and JLS #15.12.2:

• an identity conversion (§5.1.1)
• a widening primitive conversion (§5.1.2) ==> printIt(double) works here
• a widening reference conversion (§5.1.5)
• a boxing conversion (§5.1.7) optionally followed by widening reference conversion ==> printIt(Float) would be called here if there was no printIt(double)
• an unboxing conversion (§5.1.8) optionally followed by a widening primitive conversion.