How to interpret “public T readObjectData(… Class type)” in Java?

Question

I have this Java code.

public  T readObjectData(ByteBuffer buffer, Class type) {
...
T retVal = (T) summaries;
return retVal;

Answer 1

is a parameter class. There is no class named T. You can use this method with any class specified via second method argument named type.

since method is defined as following:

public T readObjectData(ByteBuffer buffer, Class type)

You can call it as written below:

MyClass obj = o.readObjectData(buffer, MyClass.class);

Please pay attention that you do not have to cast return value of readOjectData() to MyClass. Once upon a time, before java 5 this method would be defined as:

public Object readObjectData(ByteBuffer)

and its usage looked like:

MyClass obj = (MyClass)o.readObjectData(buffer);

Since casting may cause ClassCastException this is a bad practice. This was a reason for invention of generics.