Question

I’d like to implement a method that takes an Object as argument, casts it to an arbitrary type, and if that fails returns null. Here’s what I have so far:

public static void main(String[] args) {     MyClass a, b;     a = Main.<MyClass>staticCast(new String('B')); }  public static class MyClass { }  public static <T> T staticCast(Object arg) {     try {         if (arg == null) return null;         T result = (T) arg;         return result;     } catch (Throwable e) {         return null;     } } 

Unfortunately the class cast exception is never thrown/caught in the body of the staticCast() function. It seems Java compiler generates the function String staticCast(Object arg) in which you have a line String result = (String) arg; even though I explicitly say that the template type should be MyClass. Any help? Thanks.

Answer 1

Because generic type information is erased at runtime, the standard way to cast to a generic type is with a Class object:

public static <T> T staticCast(Object arg, Class<T> clazz) {     if (arg == null) return null;     if (!clazz.isInstance(arg))         return null;     T result = clazz.cast(arg);     return result; } 

Then call it like this:

a = Main.staticCast('B', MyClass.class);