Primitive Converstions

[Thomas Markl]

Hello,
this is about a conversion from int to byte and int to double.
Why does iftest1a work and iftest1b doesn’t?
What must be done to get iftest1b to work properly?

class IF {
 int i=3;
    public void ifdo(double a) {
    if (i < a)
    System.out.println("i < a");
  }
}
 
public class IFtest1a {
 public static void main (String args[]) {
 IF if1 = new IF();
 if1.ifdo(9);
 }
}

Compiles and runs with result: „i < a“

class IF {
 int i=3;
  public void ifdo(byte a) {
  if (i < a)
    System.out.println("i < a");
  }
}
 
public class IFtest1b {
 public static void main (String args[]) {
 IF if1 = new IF();
 if1.ifdo(9);
 }
}
 
C:\Java\EigeneJavaProgramme>javac IFtest1.java 
IFtest1.java:12: ifdo(byte) in IF cannot be applied to (int)
 if1.ifdo(9);
    ^
1 error

[ edited to preserve formatting using the [code] and [/code] UBB tags -ds ]
[ July 24, 2002: Message edited by: Dirk Schreckmann ]

[Neil Laurance]

Primitives can be automatically converted if the new primitive is 'wider'. So the following is possible:
int (32 bits) -> double (64 bits)
However, you cannot automatically convert to a narrower primitive. This is not possible:
int (32 bits) -> byte (8 bits)
To do this, you must use an explicit cast expression:
int i = 3;
byte b = (byte)i;
Cheers, Neil
[ July 24, 2002: Message edited by: Neil Laurance ]