设计模式之组合模式

意图

将对象组合成部分-整体的树形结构，组合模式使得用户对单个对象和组合对象使用具有统一性。它在我们树型结构的问题中，模糊了简单元素和复杂元素的概念，客户程序可以像处理简单元素一样来处理复杂元素，从而使得客户程序与复杂元素的内部结构解耦。

实现

创建employee实体类

public class Employee {
    private String name;
    private String dept;
    private int salary;
    private List<Employee> subordinate;

    public Employee(String name, String dept, int salary) {
        this.name = name;
        this.dept = dept;
        this.salary = salary;
        this.subordinate = new ArrayList<>();
    }

    public void add(Employee employee) {
        subordinate.add(employee);
    }

    public void remove(Employee employee) {
        subordinate.remove(employee);
    }

    public List<Employee> getSubordinate(){
        return subordinate;
    }

    public String toString(){
        return ("Employee :[ Name : "+ name
                +", dept : "+ dept + ", salary :"
                + salary+" ]");
    }
}

创建和打印结构层次

public class CompositePatternDemo {
    public static void main(String[] args) {
        Employee CEO = new Employee("John","CEO", 30000);

        Employee headSales = new Employee("Robert","Head Sales", 20000);

        Employee headMarketing = new Employee("Michel","Head Marketing", 20000);

        Employee clerk1 = new Employee("Laura","Marketing", 10000);
        Employee clerk2 = new Employee("Bob","Marketing", 10000);

        Employee salesExecutive1 = new Employee("Richard","Sales", 10000);
        Employee salesExecutive2 = new Employee("Rob","Sales", 10000);

        CEO.add(headSales);
        CEO.add(headMarketing);
        headMarketing.add(salesExecutive1);
        headMarketing.add(salesExecutive2);
        headSales.add(clerk1);
        headSales.add(clerk1);

        System.out.println(CEO);
        for (Employee heademployee : CEO.getSubordinate()) {
            System.out.println(heademployee);
            for (Employee employee : heademployee.getSubordinate()) {
                System.out.println(employee);
            }
        }
    }
}

结果

Employee :[ Name : John, dept : CEO, salary :30000 ]
Employee :[ Name : Robert, dept : Head Sales, salary :20000 ]
Employee :[ Name : Laura, dept : Marketing, salary :10000 ]
Employee :[ Name : Laura, dept : Marketing, salary :10000 ]
Employee :[ Name : Michel, dept : Head Marketing, salary :20000 ]
Employee :[ Name : Richard, dept : Sales, salary :10000 ]
Employee :[ Name : Rob, dept : Sales, salary :10000 ]