Ordinal Coparisons Question

[Lydia Zhang]

Hi guys,
I don't underestand why this code works? How to compare char to int, char to float?

  
public class Test{
 public static void main(String argv[]){
 int p = 9;
 int q = 65;
 int r = -12;
 float f = 9.0f;
 char c = 'A';
 
 if (f<=c) 
   System.out.println("f is small or equals to c");
 if (c>r)
   System.out.println("c is greater than r");
 if (c>=q)
   System.out.println("c is greater or equals to q.");
 }
}

[Francisco A Guimaraes]

when dealing with non-boolean primitives, you can compare any of them with any other, because the smaller operand is promoted to the type of the greater.
Francisco

[Francisco A Guimaraes]

I found a more precise rule in the JLS 5.6.2:

If either operand is of type double, the other is converted to double.

Otherwise, if either operand is of type float, the other is converted to float.

Otherwise, if either operand is of type long, the other is converted to long.

Otherwise, both operands are converted to type int.

[]�s
Francisco

[Lydia Zhang]

Thanks Francisco!
But I'm still confused of how to promote the char 'A' to int or float? Can you give me an example?

[Jose Botella]

There is a chapter in JLS 5 about conversions and promotions.

Let's say 'A' char is 0041 in hex (two bytes)
To convert to a bigger type add enough zeros to its left up to the number of digits in the target type:
0000 0041 This is an int (4 bytes) with the same value as the char 'A'.
If the number is negative you will have to add 1s instead.
Review the binary, hexadecimal and two's complement
formats if needed.

[Lydia Zhang]

Thanks Jose! The binary is my weakest point, I really don't know how to display a number into binary... I'll review it.