Java - Generics with lists

Question

I wrote a function for my cache to retrieve a specific object. This way I don\'t need to cast it .

@SuppressWarnings(\"unchecked\")
    public static 

        

Answer 1

Just to clarify Joe's answer ( I don't have enough reputation to comment), at runtime there is no difference between a List <String> and List<Integer> or any other type of List, generics aren't kept at runtime.

Meaning, List<String>.class is completely identical to List<Integer>.class and is actually List.class. This is a weakness of the Java type system. I'm not familiar with a simple way to implement what you wish for.

A code proof for the heck of it :

// It is true that      
    List<String> stringList = new ArrayList<String>(); 
    List<Integer> integerList = new ArrayList<Integer>();                                               
    System.out.println( stringList.getClass() == integerList.getClass()  );

    // And that ... 
    List objectList = new ArrayList();
    System.out.println( stringList.getClass() == objectList.getClass()  );

    //However, the following is false because a different implementation is used ( I wanted a false case)
    List objectLinkedList = new LinkedList();
    System.out.println(  objectLinkedList.getClass() == objectList.getClass() );

Answer 2

You can't get class of List<String>, in your case the only way is:

List<String> ipList = (List<String>)Util.inCache(List.class, title);

Answer 3

There is a concept in java called type erasure. Due to legacy reasons, something like List is just a list. It doesn't remember that it is a list of string at run time. You should just write List.class.

You can then specify the type of object in the List when iterating through it.

Answer 4

You can try :

List<String> ipList = Util.inCache(List.class, title);

Answer 5

Try this-

List<String> inList = (List<String>)Test.inCache(List.class, title);

And you can do also -

List<String> inList = Test.inCache((Class<? extends List<String>>)List.class, token);