extends vs implements in java

in java, the keywords `extends` and `implements` are used for inheritance and interface implementation, respectively. understanding the difference between these two is crucial for designing robust object-oriented applications.

1. `extends`

the `extends` keyword is used when a class is inheriting from another class. this is known as class inheritance. a subclass (child class) can inherit fields (attributes) and methods from a superclass (parent class). java allows single inheritance, meaning a class can only extend one other class.

example of `extends`

**output:**

2. `implements`

the `implements` keyword is used when a class is implementing an interface. an interface is a reference type in java that is similar to a class, but it can only contain constants, method signatures, default methods, static methods, and nested types. interfaces do not contain instance fields. a class can implement multiple interfaces, which allows for a form of multiple inheritance.

example of `implements`

**output:**

key differences between `extends` and `implements`

1. **inheritance vs. implementation**:
- `extends` is used for class inheritance (class to class).
- `implements` is used for implementing an interface (class to interface).

2. **number of classes/interfaces**:
- a class can only extend one other class (single inheritance).
- a class can implement multiple interfaces, allowing for multiple inheritance of type.

3. **method implementation**:
- when a subclass extends a superclass, it inherits the methods and can override them.
- when a class implements an interface, it must provide implementations for all the methods declared in the interface.

4. **use cases**:
- use `extends` when you want to create a new class based on an existing class (i.e., it is a type of that class).
- use `implements` when you want to define a contract for a class without enforcing a class hierarchy.

summary

in java, `extends` is for class inheritance, all ...

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