Java: double vs float

Question

In another Bruce Eckel exercise, the code I've written takes a method and changes value in another class. Here is my code:

class Big {   float b; }  public class PassObject {   static void f(Letter y) {     y.c = 'z';   } //end f()   static void g(Big z) {     z.b = 2.2;   }    public static void main(String[] args ) {     Big t = new Big();     t.b = 5.6;     System.out.println("1: t.b : " + t.b);     g(x);     System.out.println("2: t.b: " + t.b);   } //end main }//end class 

It's throwing an error saying "Possible loss of precision."

PassObject.java:13: possible loss of precision found: double required : float   z.b = 2.2 passobject.java:20: possible loss of precision found : double required : float   t.b = 5.6 

Can't doubles be floats as well?

Answer 1

Yes, but you have to specify that they are floats, otherwise they are treated as doubles:

z.b = 2.2f 

The 'f' at the end of the number makes it a float instead of a double.

Java won't automatically narrow a double to a float.

Answer 2

No, floats can be automatically upcast to doubles, but doubles can never be floats without explicit casting because doubles have the larger range.

float range is 1.40129846432481707e-45 to 3.40282346638528860e+38

double range is 4.94065645841246544e-324d to 1.79769313486231570e+308d