UML Learning: Association relationships (aggregations, combinations) of class diagram classes

The Concept of association

An association is used to represent a structural relationship between objects of two or more classes, which is represented in code as a class that contains the application of one or more objects to another class as a property.

Program Demo: Association relationship (Code/assocation)

Suppose: A company has only three employees: an employee either has no job or can only work in a company. (Code is simplified, the main description of the association relationship)

Person class:

Class person
    {public
        string name;
        Public person (string ename)
        {
            name = ename;
        }
        public void Startwork ()
        {
            Console.WriteLine ("Employee {0} starts working", name);
        }
    
Person

Company class:

Class company
    {public
        string name;     Company name Public
      person[] employee = new PERSON[3]; 
         
        Public Company (string cName)  //constructor
        {
            name = CName;
        }
    
        public void Run ()
        {
            Console.WriteLine ("Company" {0} "started operation", name);
            Employee[0].startwork ();
            Employee[1].startwork ();
            Employee[2].startwork ();
        }
    
        public void Stop ()
        {
            Console.WriteLine ("Company" {0} "stop working", name);
        }
    
Company

Console program:

Class program
    {
        static void Main (string[] args)
        {
            Group C = new Company ("Beijing Capacity Limited");
            C.employee[0] = new Person ("John");
            C.EMPLOYEE[1] = new Person ("Dick");
            C.EMPLOYEE[2] = new Person ("Wang er");
            C.run ();
            C.stop ();
            Console.read ();
        }
    
Program

Output:

The corresponding class diagram: