Composite パターン - コンポジットパターン

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


//Component抽象クラスに相当する IFile.java
interface IFile {
    public void printName();
    
    //子供追加
    public boolean addChild(IFile file);
    //子供削除
    public boolean removeChild(IFile file);
    //子供取得
    public List<IFile> getChildren();
}

//Leaf（葉）クラスに相当する　File.java
class File implements IFile {
    private String name;
    
    public File(String name) {
        this.name = name;
    }
    public void printName() {
        System.out.println(name);
    }

    //子供はないので、空実装
    public boolean addChild(IFile file) {
        return false;
    }

    //子供はないので、空実装
    public boolean removeChild(IFile file) {
        return false;
    }

    //子供はないので、空実装
    public List<IFile> getChildren() {
        return null;
    }
    
}

//Composite（枝）クラスに相当する　Folder
class Folder implements IFile {
    private String name;
    private List <IFile> childList;
    
    public Folder(String name) {
        this.name = name;
        this.childList = new ArrayList<IFile>();
    }
    public void printName() {
        System.out.println(name);
    }

    //子供追加
    public boolean addChild(IFile file) {
        return childList.add(file);
    }

    //子供削除
    public boolean removeChild(IFile file) {
        return childList.remove(file);
    }

    //子供取得
    public List<IFile> getChildren() {
        return childList;
    }
}

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

public class Client {
    public static void main(String[] args) {
        
        //再帰的なデータ構造を構築
        Folder rootFolder = new Folder("c:\\");
        Folder compositeFolder = new Folder("composite");
        rootFolder.addChild(compositeFolder);
        Folder windowsFolder = new Folder("windows");
        rootFolder.addChild(windowsFolder);
        File file = new File("TestComposite.java");
        compositeFolder.addChild(file);
        
        //再帰的なデータ構造をアクセス
        printTree(rootFolder);
    }
    
    private static void printTree(IFile ifile) {
        ifile.printName();
        List <IFile> children = ifile.getChildren();
        
        for (IFile file:children) {
            if (file instanceof File) {
                System.out.print("  ");
                file.printName();
            } else if (file instanceof Folder) {
                printTree(file);    //再帰
            }
        }
    }
}