Is there a way to cast an object to return value of a method? I tried this way but it gave a compile time exception in "instanceof" part:
public static <T> T convertInstanceOfObject(Object o) {
if (o instanceof T) {
return (T) o;
} else {
return null;
}
}
I also tried this one but it gave a runtime exception, ClassCastException:
public static <T> T convertInstanceOfObject(Object o) {
try {
T rv = (T)o;
return rv;
} catch(java.lang.ClassCastException e) {
return null;
}
}
Is there a possible way of doing this easily:
String s = convertInstanceOfObject("string");
System.out.println(s); // should print "string"
Integer i = convertInstanceOfObject(4);
System.out.println(i); // should print "4"
String k = convertInstanceOfObject(345435.34);
System.out.println(k); // should print "null"
EDIT: I wrote a working copy of the correct answer:
public static <T> T convertInstanceOfObject(Object o, Class<T> clazz) {
try {
return clazz.cast(o);
} catch(ClassCastException e) {
return null;
}
}
public static void main(String args[]) {
String s = convertInstanceOfObject("string", String.class);
System.out.println(s);
Integer i = convertInstanceOfObject(4, Integer.class);
System.out.println(i);
String k = convertInstanceOfObject(345435.34, String.class);
System.out.println(k);
}
You have to use a Class
instance because of the generic type erasure during compilation.
public static <T> T convertInstanceOfObject(Object o, Class<T> clazz) {
try {
return clazz.cast(o);
} catch(ClassCastException e) {
return null;
}
}
The declaration of that method is:
public T cast(Object o)
This can also be used for array types. It would look like this:
final Class<int[]> intArrayType = int[].class;
final Object someObject = new int[]{1,2,3};
final int[] instance = convertInstanceOfObject(someObject, intArrayType);
Note that when someObject
is passed to convertToInstanceOfObject
it has the compile time type Object
.