16. 组合模式

### 16. 组合模式
> 又叫部分整体模式，是用于把一组相似的对象当作一个单一的对象。组合模式依据树形结构来组合对象，用来表示部分以及整体层次。这种类型的设计模式属于结构型模式，它创建了对象组的树形结构。

- **主要解决**：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。

以创建和打印员工的层次结构为例，最小单元示例：

- 1、创建 Employee 类，该类带有 Employee 对象的列表。

```java
	public class Employee {
	
	    private String name;
	    // 部门
	    private String dept;
	    // 工资
	    private int salary;
	    // 员工 list
	    private List<Employee> subordinates;
	
	    public Employee(String name, String dept, int salary) {
	        this.name = name;
	        this.dept = dept;
	        this.salary = salary;
	        this.subordinates = new ArrayList<Employee>();
	    }
	
	    public void add(Employee e) {
	        subordinates.add(e);
	    }
	
	    public void remove(Employee e) {
	        subordinates.remove(e);
	    }
	
	    public List<Employee> getSubordinates() {
	        return subordinates;
	    }
	
	    @Override
	    public String toString() {
	        return "Employee{" +
	                "name='" + name + '\'' +
	                ", dept='" + dept + '\'' +
	                ", salary=" + salary +
	                ", subordinates=" + subordinates +
	                '}';
	    }
	}
	```

- 2.使用 Employee 类来创建和打印员工的层次结构。

```java
    final 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);

headSales.add(salesExecutive1);
    headSales.add(salesExecutive2);

headMarketing.add(clerk1);
    headMarketing.add(clerk2);
    
    Log.e("---", ceo.toString());
    
    // 打印
    /*
     * Employee{name='John', dept='CEO', salary=30000,
     * subordinates=[Employee{name='Robert', dept='Head sales', salary=20000,
     * subordinates=[
     * Employee{name='Richard', dept='Sales', salary=10000, subordinates=[]},
     * Employee{name='Rob', dept='Sales', salary=10000, subordinates=[]}]},
     * Employee{name='Michel', dept='Head Marketing', salary=20000,
     * subordinates=[Employee{name='Laura', dept='Marketing', salary=10000, subordinates=[]},
     * Employee{name='Bob', dept='Marketing', salary=10000, subordinates=[]}]}]}
     */
	```