Boolean type as String within generics

[nimo frey]

I have this:

private Map<String, Boolean> myMap;

When I do this:

System.out.print(myMap.get("value"));

then it prints out:

true

I use generics, so I allow, that instead of the boolean-value a String-value can be inserted.

Now, when I do that:

if(myMap.get("value")) {..}

then I get a classCastException because of my value (which is a string).

So I have to convert my String to boolean with:

boolean bool = Boolean.parseBoolean(myMap.get("value"));

but it does not work. I even get the same classcastexception:

Caused by: java.lang.ClassCastException: java.lang.String

I cannot use the class.getName()... as I get the same failure as above, when I use this method.

So how can I enforce a convert from String to Boolean within generics, when I know, that the value is a String?
[ December 02, 2008: Message edited by: nimo frey ]

[Joanne Neal]

Originally posted by nimo frey:

Now, when I do that:

if(myMap.get("value")) {..}

then I get a classCastException because of my value (which is a string).

You shouldn't get a CCE here. get will return a Boolean which will be unboxed into a boolean. It works for me.

So I have to convert my String to boolean with:

boolean bool = Boolean.parseBoolean(myMap.get("value"));

but it does not work.[/QB]

This won't work because the get() is returning a Boolean and parseBoolean expects a String as an argument.

Originally posted by nimo frey:
So how can I enforce a convert from String to Boolean within generics, when I know, that the value is a String?

What are you trying to convert from String to Boolean ? There shouldn't be any need to do this.
[ December 02, 2008: Message edited by: Joanne Neal ]

[Jelle Klap]

What did you mean when you said:

Originally posted by nimo frey:
I use generics, so I allow, that instead of the boolean-value a String-value can be inserted.

The way I interpret this sentence is that you are able to insert both Boolean and String objets as values in the Map, indicating that somehow you're circumventing the compile-time type checking mechanism. You should be getting type safety warnings if that's the case.

[nimo frey]

okay, it works now.

However, I have thought, that generics are not absolutely type-save.

[Campbell Ritchie]

Generics are type-safe, as long as you don't suppress or ignore any warnings from the compiler.