设计模式：组合模式示例

组合模式的典型例子通常涉及到树形结构的处理，下面是几个形象且易于理解的例子：

文件系统

在文件系统中，目录可以包含文件或者其他目录，但是从用户的角度来看，目录和文件都可以被“打开”或者“获取大小”。这里的目录就是一个组合对象，文件是叶子节点。

interface FileSystemItem {void showProperties();long getSize();
}class File implements FileSystemItem {private String name;private long size;public File(String name, long size) {this.name = name;this.size = size;}@Overridepublic void showProperties() {System.out.println("File: " + name + " (Size: " + size + ")");}@Overridepublic long getSize() {return size;}
}class Directory implements FileSystemItem {private String name;private List<FileSystemItem> children = new ArrayList<>();public Directory(String name) {this.name = name;}public void add(FileSystemItem item) {children.add(item);}@Overridepublic void showProperties() {System.out.println("Directory: " + name);for (FileSystemItem child : children) {child.showProperties();}}@Overridepublic long getSize() {long size = 0;for (FileSystemItem child : children) {size += child.getSize();}return size;}
}

图形界面组件

在图形用户界面（GUI）中，容器组件可以包含其他容器组件或者叶子组件（如按钮、文本框等）。无论是容器还是叶子组件，都可以对它们执行某些操作，如绘制、启用/禁用等。

interface GUIComponent {void render();
}class Button implements GUIComponent {@Overridepublic void render() {System.out.println("Render Button");}
}class Panel implements GUIComponent {private List<GUIComponent> children = new ArrayList<>();public void add(GUIComponent component) {children.add(component);}@Overridepublic void render() {System.out.println("Render Panel");for (GUIComponent child : children) {child.render();}}
}

组织结构

在组织结构中，公司可以分为部门，部门下可以有子部门或员工。部门和员工都可以执行某些操作，如获取成本。

interface OrganizationComponent {void printStructure();double getCost();
}class Employee implements OrganizationComponent {private String name;private double salary;public Employee(String name, double salary) {this.name = name;this.salary = salary;}@Overridepublic void printStructure() {System.out.println("Employee: " + name + ", Salary: " + salary);}@Overridepublic double getCost() {return salary;}
}class Department implements OrganizationComponent {private String name;private List<OrganizationComponent> members = new ArrayList<>();public Department(String name) {this.name = name;}public void add(OrganizationComponent component) {members.add(component);}@Overridepublic void printStructure() {System.out.println("Department: " + name);for (OrganizationComponent member : members) {member.printStructure();}}@Overridepublic double getCost() {double cost = 0;for (OrganizationComponent member : members) {cost += member.getCost();}return cost;}
}