primitive casting

[jibs parap]

   
class Test2 {
byte b = 125; //line1 no casting needed
String doThis(byte c) { return "hello";}
 
}
class Test {
public static void main(String... args) {
 System.out.println(new Test2().doThis(100)); //line2 casting needed
}
}

Can anyone please explain casting needed in line2 but not in line1 for successful compilation even though both appear to have similar issue-converting int to byte.

[Dave Walsh]

Wild guessing here, I haven't even tried it (too lazy ). I'm putting my java intuition to the test.

Could it be an assignment matter ? On line 1, the compiler can see that the value, although an int literal, holds in a byte (less than 127). So no casting needeed When you pass a parameter to a function, it's a type problem. All the compiler cares about is that types are compatible and in that case, you must downcast an int to a byte.

Please correct me if required !

[Priyam Srivastava]

when it comes to assignment i.e byte b = 100, the compiler sees whether the value is in range or not and if not then gives compilation error.

but in case of passing values in methods, the least you can pass is an int literal..not byte not short
hence when you say :

 
String doThis(byte b) {
//do some stuff
}
.
.
.
.
.
doThis(100)

then you are actually passing a int literal and trying to assign it to a byte..which cannot be done implicitly and hence you need to downcast it to byte like:

doThis((byte)100)