'Substitution Principle' By Barbara Liskov

~ One of the most important SOLID Principle, well known for its capability to increase efficiency in OOP Language like Java - 'Liskov's Substitution Principle' can be described in two statements :-

1. If for each object 1 of type S there is an object 2 of type T such that for all programs P defined in terms of T, the behavior of P is unchanged when 1 is substituted for 2 then S is a subtype of T.
2. Subtypes must be substitutable for their base types.

~ Suppose, in Java coding terms, we should distribute classes into parent - child relationship. By using Java's Major Pillar - Inheritance, we can keep some common methods in parent class / interface and can be implemented in the child classes.

~ For example :-

~ The above example can be considered as one of the pragmatic example in Web Development. In which, Microservices can be programmed using LSP. The reason why we usually have to replace a microservice is that there is a new version of it. So, if my entity is a microservice, the equivalent entity is the new version of it. So, applying LSP to microservices, we don’t want to break existing clients of the service, but replace it with a better or enhanced one.

~ Benefits Of LSP :-

1. Reusability :- Code can be reused quite easily with such a valuable concept and can save time for use.
2. Interchangeability :- We can create a set of related classes that can be used interchangeably without modifying the code.