Java Generics Type Erasure byte code

Question

As per the java documentation on Erasure of Generic Types,

Consider the following generic class that represents a node in a singly linked list:

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Answer 1

The fact that the class is generic is retained. For instance, at runtime you can call

Node.class.getTypeParameters()

The next bit of code will return "T".

(new Node()).getClass().getTypeParameters()[0].getName()

You can't get the value of type parameters at runtime, but the JVM knows they're there.

Erasure comes into play when you construct a instance.

Node node = new Node(1, null);
Integer i = node.getData();

Becomes

Node node = new Node(1, null);
Integer i = (Integer)node.getData();

Generic classes are always generic. But instances do not carry generic type information inside them. The compiler verifies that everything you've done agrees with the generic type and then inserts casts.