import java.util.ArrayList;
import java.util.List;

（1） class AbstractFile {
    protected String name;
    public void printName() { System.out.println(name); }
    public abstract boolean addChild(AbstractFile file);
    public abstract boolean removeChild(AbstractFile file);
    public abstract List<AbstractFile> getChildren();
}

class File extends AbstractFile {
    public File(String name) { this.name = name; }
    public boolean addChild(AbstractFile file) { return false; }
    public boolean removeChild(AbstractFile file) { return false; }
    public List<AbstractFile> getChildren() { return （2）; }
}

class Folder extends AbstractFile {
    private List<AbstractFile> childList;
    public Folder(String name) {
        this.name = name;
        this.childList = new ArrayList<AbstractFile>();
    }
    public boolean addChild(AbstractFile file) { return childList.add(file); }
    public boolean removeChild(AbstractFile file) {return childList.remove(file); }
    public （3）<AbstractFile> getChildren() { return （4）; }
}

public class Client {
    public static void main(String[] args) {
        // 创造一个树形的文件/目录结构
        AbstractFile rootFolder = new Folder("c:\\");
        AbstractFile compositeFolder = new Folder("composite");
        AbstractFile windowsFolder = new Folder("windows");
        AbstractFile file = new File("TestComposite.java");
        rootFolder.addChild(compositeFolder);
        rootFolder.addChild(windowsFolder);
        compositeFolder.addChild(file);
        // 打印目录文件数
        printTree(rootFolder);
    }

    private static void printTree(AbstractFile ifile) {
        ifile.printName();
        List<AbstractFile> children = ifile.getChildren();
        if (Children == null) return;
        for (AbstractFile file : Children) {
            （5）;
        }
    }
}