What does the <E> syntax mean in Java?

These are called Generics.

In general, these enable types (classes and interfaces) to be parameters when defining classes, interfaces and methods.

Using generics give many benefits over using non-generic code, as shown the following from Java's tutorial:

• Stronger type checks at compile time. A Java compiler applies strong type checking to generic code and issues errors if the code violates type safety. Fixing compile-time errors is easier than fixing runtime errors, which can be difficult to find.

  For example:

  // without Generics
  List list = new ArrayList();
  list.add("hello");
  
  // With Generics
  List<Integer> list = new ArrayList<Integer>();
  list.add("hello"); // will not compile
  

• Enabling programmers to implement generic algorithms. By using generics, programmers can implement generic algorithms that work on collections of different types, can be customized, and are type safe and easier to read.

• Elimination of casts.

  For example, the following code snippet without generics requires casting:

  List list = new ArrayList();
  list.add("hello");
  String s = (String) list.get(0);
  

  When re-written to use generics, the code does not require casting:

  List<String> list = new ArrayList<String>();
  list.add("hello");
  String s = list.get(0); // no cast
  

Here <E> denotes the type parameter of Node class .The type parameter defines that it can refer to any type (like String, Integer, Employee etc.). Java generics have type parameter naming conventions like following:

1. T - Type
2. E - Element

3. K - Key

4. N - Number

5. V - Value

For example take the following scenerio

public class Node<E>{
   E elem;
   Node<E> next, previous;
}
class Test{
   Node<String> obj = new Node<>();
}

For the above scenerio, in background the Node class 'E' will reference the String type and class will be look like following

public class Node<String>{
   String elem;
   Node<String> next,previous;
}

Not only String you can also use Integer,Character,Employee etc as a type parameter.

You can use generics with Interface,method and constructor too.

For more about generics visit these:

https://www.journaldev.com/1663/java-generics-example-method-class-interface https://www.javatpoint.com/generics-in-java

Node imply 'Generics' class.

Refer : http://docs.oracle.com/javase/tutorial/java/generics/types.html