Advanced Java Concepts

All the Advanced Java Concepts

1. Generic Methods in Java

• Generics means parameterized types.
• Using Generics, it is possible to create classes that work with different data types.

2. Variable length of arguments to methods

• The varrags allows the method to accept zero or muliple arguments.
• The main advantage is that, we don't have to provide overloaded methods so less code.
• Can pass any length of arguments to this method

3. Substitution Principles in Java

• In Java, we can pass derived class object into base class type, because it is actually derived from the same Base class.
• But it is not applicable in case of arrays or any type of lists.

4. Use of wildcard Characters

• The question mark (?) is known as the wildcard in generic programming.
• It represents an unknown type.
• The wildcard can be used in a variety of situations such as the type of a parameter, field, or local variable; sometimes as a return type.

5. Collections Framework

• The Collection in Java is a framework that provides an architecture to store and manipulate the group of objects.
• It provides readymade architecture.
• It represents a set of classes and interfaces.
• The following image depicts hierarchy of Collection framework in Java:

6. LinkedLists

• In java, LinkedLists are doubly LinkedLists - that is they have link to next and prev both nodes
• LinkedLists are faster in adding and removing items, even in middle
• ArrayList and LinkedLists are somewhat similar, because they both have so many methods in common
• But LinkedList is faster if have to add / remove so many items at the middle
• But LinkedLists occupy more memory that the ArrayList, because has link to both next and prev

7. LinkedList Implementation of Queue

• Queue is used to keep the elements that are processed in the First In First Out (FIFO) manner.
• For example, the customers in any hotel are served in first come first serve manner.

8. HashMaps

• Java HashMap class implements the Map interface which allows us to store key and value pair, where keys should be unique.
• HashMap stores each entry in the fom of key:value pair, which same as the Dictionary in Python.
• Hashmaps are unordered, are accessed using their keys only.
• HashMap does not retain its order

9. LinkedHashMaps

• Linkedhashmap returns the hashmap in the same order as created.
• The LinkedHashMap Class is just like HashMap with an additional feature of maintaining an order of elements inserted into it.