Inner class is a class within another class, method or block. An inner class can be one of the following four types: Anonymous, Local, Member and Nested top-level. 

In object oriented programming or in Unified Modelling, relationships between objects can be classified as association, aggregation, composition and inheritance. 

Association

Association is a relationship between two objects. Here objects might not be completely dependent on each other.

Strings are immutable and a new String object is created every time you modify a Sring object. A StringBuffer is a thread-safe, mutable sequence of characters. A StringBuilder is similar to StringBuffer, but with no guarantee of synchronization.

We will discuss String Replace and String Split in Java with some examples. String replace is the process by which we replace parts of a string with another string. Some Java methods directly accept character sequences, while some others accept a regular expression (regex). We will discuss some of these approaces using examples. String split is the process by which a string is split around a delimiter.