面试题与答案

OOP is a programming paradigm that uses objects to organize code. It involves concepts like encapsulation, inheritance, and polymorphism.

Inheritance is a mechanism where a new class inherits properties and behaviors from an existing class. It promotes code reusability and establishes a relationship between classes.

A constructor is a special method in a class that is automatically called when an object of the class is created. It is used for initializing object properties.

Example:

class Car {
  constructor(make, model) {
    this.make = make;
    this.model = model;
  }
}

The 'super' keyword is used to call the constructor or methods of the parent class in a subclass. It is often used to access the superclass's methods or properties.

Example:

class Child extends Parent {
  constructor() {
    super();
  }
}

The 'this' keyword refers to the current instance of the class. It is used to access the current object's properties and methods within that class.

Example:

class Person {
  constructor(name) {
    this.name = name;
  }
  greet() {
    console.log('Hello, ' + this.name + '!');
  }
}

A static method is a method that belongs to the class rather than an instance of the class. It is called on the class itself, not on an object created from the class.

Example:

class MathUtils {
  static add(a, b) {
    return a + b;
  }
}

In Java, an interface is a collection of abstract methods. A class implements an interface, providing concrete implementations for all its methods. It allows for achieving multiple inheritance in Java.

Example:

interface Printable {
  void print();
}

The 'super()' statement is used in a subclass constructor to call the constructor of its superclass. It initializes the inherited properties and ensures that the superclass's constructor is executed before the subclass's constructor.

Example:

class Subclass extends Superclass {
  constructor() {
    super();
  }
}

In C#, the 'sealed' keyword is used to prevent a class from being inherited. It ensures that the class cannot be used as a base class for other classes.

Example:

sealed class MySealedClass {
  // class content
}