Types of Java generics are not erased

We all know that Java source code will erase the generic information after compiling, now see a generic type is not erased, see the Concurrenthashmap.comparableclassfor method.

Parameterizedtype.getactualtypearguments can get generic information that is not erased in the interface implemented by the class. The experiment is as follows:

 Public classParameterized { Public Static voidMain (string[] args) {type[] types= Integer.class. Getgenericinterfaces ();//type[] types = HashMap.class.getGenericInterfaces ();         for(Type Type:types) {System.out.println (type); if(TypeinstanceofParameterizedtype) { Parameterizedtype P = (parameterizedtype) type; System.out.println ("-rawtype:" +P.getrawtype ()); System.out.println ("-ownertype:" +P.getownertype ()); type[] Typeargs = p.getactualtypearguments (); System.out.println ("-actualtypearguments:" +arrays.tostring (Typeargs)); }        }    }}

Output:

Integer.class

Interfacenull -actualtypearguments:[class Java.lang.Integer]

Hashmap.class

Interfacenull -actualtypearguments:[k, V]interface  Java.lang.CloneableInterface java.io.Serializable

Types of Java generics are not erased