type conversion

[Jason Attin]

HI guys, given this codefrom Glenn, Mitchell. OCAJP Oracle Certified Associate Java SE 8 Programmer Practice Exams (Kindle Locations 10550-10552). Enthuware. Kindle Edition,

public void switchTest( byte x){ switch( x){ case 'b': // 1 default : // 2 case -2: // 3 case 80: // 4 }

apparently compiles because a char (b) is essentially a number. SO that got me thinking and I tried something:

char mtChar = 'b';
byte myByte = mtChar;

That is essentially the same as above, but it doesn't compile. I mean a char is 16bits and a byte is only 8 so fair enough if it doesn't compile, but then why does it work in the switch statement?

[Henry Wong]

First, these are two different java statements/features, which have different rules, so comparing why one works while the other is a compiler error, doesn't make too much sense.

However, if you are asking why the compiler knows that the first is a valid comparison while the other is not a valid assignment... In the first case (no pun intended), the value being checked is a compile time constant, and hence, can be confirm to be in range. In the second case, neither is a compile time constant, and hence, can't be implicitly converted.

Henry

[Jason Attin]

OK thanks for clarifying it

[Mala Gupta]

An interesting observation, Jason.

I modified your code. Do you think the following modified version of your code will compile?

	final char mtChar = 'b';
	byte myByte = mtChar;

Thanks.

With much respect,
Mala

[Jason Attin]

Without trying the code, probably not because char is a 16 bits and byte is 8