Creational Patterns : Builder

Properties:

-          Helps simplifying  creation of complex objects having constructers with many paramters.

-          Creates a fluent interface  which makes code more readable.

-          Can be identified easily by mehods returning reference to itself and a build method which returns reference of the target object.

Implementation:

-          An interface defines which methods should builders have.

-          Implementing builders may come with different building strategies.

-          Each method in builder takes a parameter and returns reference of it self, so that methods can be chained.

-          Finally a build method is provided to build actual object.

Java Standard Library Implementations:

-          java.lang.StringBuilder

-          java.lang.StringBuffer

Example Usage:

// A builder typically lets method chaining

StringBuilder sb=new StringBuilder()

                .append("String1 ")

                .append(123)

                .insert(5,"Middle");

// after setting build parameters,

//object instance can be built using build method

sb.toString();