什么是组合模式

• Composite Design Pattern
• 主要处理树形结构数据，可以理解为一组对象集合。
• 将一组对象组织成树形结构，以表示“部分”、“整体”的层次结构。
• 组合让客户端可以统一单一对象和组合对象的处理逻辑。

组合模式的应用场景

• 部门和员工关系
• Linux 系统中的文件系统

组合模式条件

• 组合模式，将一组对象组织成树形结构，将单个对象和组合对象都看作树中的节点，以统一处理逻辑，并且它利用树形结构的特点，递归处理每个子树，一次简化代码实现。
• 使用组合模式的前提是，你的业务场景必须能够表示成树形结构。

代码实现

public interface IEmployee {

  public void add(IEmployee employee);

  public void reemove(IEmployee employee);

  public IEmployee getChild(int i);

  public String getName();

  public double getSalary();

  public void print();

}

{

  private String name;
  private double salary;
  private List<IEmployee> employees = new ArrayList<>();

  public Manager(String name, double salary) {
    this.name = name;
    this.salary = salary;
  }

  @Override
  public void add(IEmployee employee) {
    employees.add(employee);
  }

  @Override
  public void reemove(IEmployee employee) {
    employees.remove(employee);
  }

  @Override
  public IEmployee getChild(int i) {
    return employees.get(i);
  }

  @Override
  public String getName() {
    return this.name;
  }

  @Override
  public double getSalary() {
    return this.salary;
  }

  @Override
  public void print() {
    System.out.println("--------------------");
    System.out.println("name: " + name);
    System.out.println("Salary: " + salary);
    System.out.println("--------------------");
    for (IEmployee ep :
         employees) {
      ep.print();
    }
  }
}

public class Developer implements IEmployee {
  private String name;
  private double salary;

  public Developer(String name, double salary) {
    this.name = name;
    this.salary = salary;
  }

  @Override
  public void add(IEmployee employee) {
    String msg = "not supported by leaf node";
    throw new UnsupportedOperationException(msg);
  }

  @Override
  public void reemove(IEmployee employee) {
    String msg = "not supported by leaf node";
    throw new UnsupportedOperationException(msg);
  }

  @Override
  public IEmployee getChild(int i) {
    String msg = "not supported by leaf node";
    throw new UnsupportedOperationException(msg);
  }

  @Override
  public String getName() {
    return this.name;
  }

  @Override
  public double getSalary() {
    return this.salary;
  }

  @Override
  public void print() {
    System.out.println("--------------------");
    System.out.println("name: " + name);
    System.out.println("Salary: " + salary);
    System.out.println("--------------------");
  }
}

public static void main(String[] args) {
  System.out.println("Hello World!");

  Developer developer1 = new Developer("001", 011);
  Developer developer2 = new Developer("002", 012);
  Developer developer3 = new Developer("003", 013);

  Manager manager = new Manager("000", 1000);
  manager.add(developer1);
  manager.add(developer2);
  manager.add(developer3);

  manager.print();

}