Liskov Substitution Principle

If B is a subtype of A, then objects of type A may be replaced with objects of type B (i.e., an object of type A may be substituted with any object of a subtype B) without altering any of the desirable properties of the program (correctness, task performed, etc.)

• For instance, if the type Cat is a subtype of Animal, then an expression of type Cat should be substitutable wherever an expression of type Animal is used.
  • Behavior Animal walks on four legs. Cat walks on four legs.
  • Attribute Animal has two eyes. Cat has two eyes.

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Backlinks

• Substitutability (cs)
• Upcasting (cs)
• SOLID (cs)
• Purpose of Inheritance (cs)