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A cast is a way of explicitly informing the compiler that you intend to make the conversion and that you are aware that data loss might occur, or the cast may fail at run time. To perform a cast, specify the type that you are casting to in parentheses in front of the value or variable to be converted.
To typecast something, simply put the type of variable you want the actual variable to act as inside parentheses in front of the actual variable. (char)a will make 'a' function as a char. // the equivalent of the number 65 (It should be the letter A for ASCII).
To declare an int variable in C++ you need to first write the data type of the variable – int in this case. This will let the compiler know what kind of values the variable can store and therefore what actions it can take. Next, you need give the variable a name. Lastly, don't forget the semicolon to end the statement!
Type casting means taking an Object of one particular type and “turning it into” another Object type. This process is called type casting a variable. This topic is not specific to Java, as many other programming languages support casting of their variable types.
The preferred technique is to use pattern matching. This allows you to gracefully handle the case that the value in question is not of the given type:
g match {
case g2: Graphics2D => g2
case _ => throw new ClassCastException
}
This block replicates the semantics of the asInstanceOf[Graphics2D] method, but with greater flexibility. For example, you could provide different branches for various types, effectively performing multiple conditional casts at the same time. Finally, you don't really need to throw an exception in the catch-all area, you could also return null (or preferably, None), or you could enter some fallback branch which works without Graphics2D.
In short, this is really the way to go. It's a little more syntactically bulky than asInstanceOf, but the added flexibility is almost always worth it.
g.asInstanceOf[Graphics2D];
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