What are the relationships between classes in Java?

First of all, in java programming, there is the following relationship between classes:

1. Dependency

2. Association (aggregation (whole and part) relationship, such as a person and a hand) and combination (the relationship between a whole and a part, such as a person and a brain))

3. Inheritance

4. Implementation

java related videos Tutorial sharing: java learning

##1. Dependence

Definition:

indicates that one class depends on another The definition of a class, the method of one class manipulates the object of another class, applies to local variables, formal parameters of the method, or calls to static methods.

Example code:

/**
 * @Description: 依赖（Dependence)的定义：表示一个类依赖于另一个类的定义，一个类的方法操纵另一个类的对象
 * 应用于局域变量、方法的形参，或者对静态方法的调用。
 * @Author: 13394
 * @CreateDate: 2018/12/18 9:54
 */
public class Cook {
    public static void cook() {
        System.out.println("做饭");
    }

    public void eat() {
        System.out.println("吃饭");
    }

}
/**
 * @Description: TODO
 * @Author: 13394
 * @CreateDate: 2018/12/18 10:09
 */
public class BeforeCook {
    //局部变量
    public void before() {
        Cook cook = new Cook();
        System.out.println("饭前>>>>>>>>>>>>>>>");
        cook.eat();
    }

    //方法的形参
    public void before(Cook cook) {
        cook.eat();
    }

    //静态方法的调用
    public void before1() {
        Cook.cook();
    }

}

2. Association

Definition:

Association relationships are generally implemented using member variables, which means that one class uses another class as a member variable to call the attributes and methods of another class.

(1) Aggregation (the relationship between the whole and the part). Aggregation member variables are mainly assigned through the set method.

Example code:

public class Cook {
    public static void cook() {
        System.out.println("做饭");
    }

    public void eat() {
        System.out.println("吃饭");
    }

}

    public class BeforeCook {
        //成员变量
       private Cook cook;
       public void setBefore(Cook cook){
           cook.eat();
       }

}

(2) Composition (the relationship between the whole and the part), member variables are mainly assigned through the construction method .

Example code:

public class BeforeCook {
     //成员变量
    Cook cook;
    public BeforeCook(Cook cook){
        this.cook=cook;
    }
   }

3. Inheritance

The relationship between classes and classes, interfaces and interfaces.

4. Implementation

The relationship between classes and interfaces.

Related article tutorial sharing:

java quick start

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