依赖和组合之间的区别?

2022-01-15 00:00:00 oop dependencies java uml composition

此处的定义

依赖

一个类的结构或行为的变化会影响其他相关的类，那么这两个类之间存在依赖关系.它需要不一样，反之亦然.当一个类包含另一个类时发生这种情况.

Change in structure or behaviour of a class affects the other related class, then there is a dependency between those two classes. It need not be the same vice-versa. When one class contains the other class it this happens.

作曲

组合是聚合的一种特殊情况.在更具体的方式，受限聚合称为组合.当一个物体包含另一个对象，如果包含的对象不存在不存在容器对象，则称为作文.

Composition is a special case of aggregation. In a more specific manner, a restricted aggregation is called composition. When an object contains the other object, if the contained object cannot exist without the existence of container object, then it is called composition.

此处 和 这里

依赖

class Employee {
    private Address address;

    // constructor 
    public Employee( Address newAddress ) {
        this.address = newAddress;
    }

    public Address getAddress() {
    return this.address;
    }
    public void setAddress( Address newAddress ) {
        this.address = newAddress;
    }
}

作曲

final class Car {

  private final Engine engine;

  Car(EngineSpecs specs) {
    engine = new Engine(specs);
  }

  void move() {
    engine.work();
  }
}

推荐答案

可以看出两个构造函数的区别:

The difference can be seen in the two constructors:

  • 依赖:Address对象来自外部，它被分配到别的地方.这意味着 Address 和 Employee 对象是分开存在的，并且只是相互依赖.

  • Dependency: The Address object comes from outside, it's allocated somewhere else. This means that the Address and Employee objects exists separately, and only depend on each other.

Composition:在这里您可以看到在inside Car 中创建了一个新的Engine.Engine 对象是 Car 的一部分.这意味着 Car 由 Engine组成.

Composition: Here you see that a new Engine is created inside Car. The Engine object is part of the Car. This means that a Car is composed of an Engine.

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