T can be either an integer or a char otherwise it should output an error(which is what i want).
My method below is trying to convert the argument from char to int or int to int.
I have no problem if there is no generic and T was int or char but since its not defined, it wont let me compile.
Is there any way to bypass this, or is there another way of converting a generic variable?
Current Code gives error:
incompatible types: T cannot be converted to int
int toReturn = gKey;
public class MyClass<T>{
private int convert(T gKey){
int toReturn = gKey;
return toReturn;
}
}
Edit1: {toReturn instead of 1} I made a mistake and corrected
Edit2: Using the extends Number solution, here are the results that I got
public static void main(String[] args) {
//test 1 for integer argument, should output 1:: success
Test<Integer> test1 = new Test<>();
int a = 1;
System.out.println(test1.convert(a));
//test 2 for character argument, should output 65 :: failure compile error
Test<Character> test2 = new Test<>();
char b = 'A';
System.out.println(test2.convert(b));
}
I am assuming that you would like to take a numeric character value such as '1' and convert it into an integer. If so, that's done simply like this:
char c = '1';
int i = Integer.parseInt(String.valueOf(c));
Of course, this conversion only work for numeric characters. Therefore, you must handle exception in some way to deal with cases when the char
parameter does not represent a number. For example:
try {
int i = Integer.parseInt(String.valueOf(c));
} catch (NumberFormatException nfe) {
// do something here
}
On the other hand, if your intent is to "convert" a char
into an int
to get the ASCII value of the character, all you need is to typecast the char
into an int
:
char c = 'a';
int i = (int) c; // i should be 97 decimal (61 hex)
I don't know why you would want that, but it is an alternative based on the plain statement you made of "converting" a char
to an int
This should be simply returning the argument. There is no "conversion" required.
Since you're using a T
as an argument, you need to do some checks in in the code.
if (arg instanceof Character)
return Integer.parseInt(String.valueOf((char)arg));
if (arg instanceof Integer)
return (int) arg;
// for all other cases, either throw exception (i.e. `IllegalArgumentException`) or return some erroneous value (i.e. if the expected return value is zero or greater, you could return -1)
Try use instanceof.
private int convert(T gKey) {
if (gKey instanceof Integer)
return ((Integer) gKey).intValue();
else
if (gKey instanceof Character)
return ((Character) gKey).charValue();
else throw new IllegalArgumentException("IllegalArgumentException");
}
private int convert(T gKey) {
if (gKey instanceof Integer)
return ((Integer) gKey).intValue();
else
if (gKey instanceof Character)
try {
return Integer.parseInt(Character.toString((Character) gKey));
}
catch (NumberFormatException e) {
throw new NumberFormatException ("NumberFormatException ");
}
else throw new IllegalArgumentException("IllegalArgumentException");
}
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