Q1. What is the difference between an interface and an abstract class?
- An interface declares a contract. It supports abstract methods plus default and static methods (Java 8+), private methods (Java 9+) and constants. A class can implement...
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Q2. What is the difference between interface and type?
Both describe the shape of an object, with subtle differences: - interface supports declaration merging and is usually preferred for public object shapes and class contra...
Q3. What is the difference between an abstract class and an interface?
An interface declares a contract: a set of method signatures with no state that any type can implement. A class can implement many interfaces, which models capability. An...
Q4. What is polymorphism and what forms does it take?
Polymorphism lets one interface be used by many implementations, so callers depend on a contract rather than a concrete type. Subtype or runtime polymorphism: a base refe...
Q5. How do interfaces work in Go, and what is the empty interface?
An interface is a set of method signatures. Any type that implements all of them satisfies the interface implicitly, with no `implements` keyword. Internally an interface...
Q6. Design a shape hierarchy so new shapes can be added without changing existing code.
Depend on an abstraction and let each shape compute its own values. ```java interface Shape { double area(); double perimeter(); } class Circle implements Shape { private...
Q7. When would you choose an interface over an abstract class?
Both define contracts that other types implement, but they differ in intent and mechanics. - An interface declares a contract with no state (traditionally) and supports m...
Q8. What is const correctness and why does it matter?
`const` is a compile-time contract. A `const` object cannot be modified, and a `const` member function promises not to modify the object, so it can be called on const obj...
Q9. How does the Dependency Inversion Principle change a design?
The Dependency Inversion Principle has two parts: high-level policy should not depend on low-level detail, and abstractions should not depend on details; details should d...
Q10. How can you define custom types or interfaces in TypeScript?
In TypeScript, custom types can be defined using interfaces or type aliases. Interfaces define the structure of an object and can be implemented by classes, while type al...