[java] 階層型enum

Client.java

package honjo;

import java.util.List;

import static honjo.OsType.*;

public class Client {

	public static void main(String[] args) {

		OsType parent = WindowsNT.parent();
		System.out.println(parent); // Windows

		System.out.println("----------");

		boolean is = Windows7.is(Unix);
		System.out.println(is); // false

		System.out.println("----------");

		List<? extends OsType> children = WindowsNT.children();
		for (OsType child : children) {
			System.out.println(child);
		}
//		WindowsNTWorkstation
//		WindowsNTServer

		System.out.println("----------");

		List<? extends OsType> allChildren = Windows.allChildren();
		for (OsType osType : allChildren) {
			System.out.println(osType);
		}
//		WindowsNT
//		WindowsNTWorkstation
//		WindowsNTServer
//		Windows2000
//		Windows2000Server
//		Windows2000Workstation
//		WindowsXp
//		WindowsVista
//		Windows7
//		Windows95
//		Windows98

		System.out.println("----------");

		boolean support = Windows7.supportsXWindowSystem();
		System.out.println(support); // false

		boolean support2 = SunOs.supportsXWindowSystem();
		System.out.println(support2); // true

		System.out.println("----------");

		boolean major = Windows2000.major();
		System.out.println(major); // false

		boolean major2 = WindowsXp.major();
		System.out.println(major2); // true

		boolean major3 = Linux.major();
		System.out.println(major3); // true

	}
}

OsType.java

package honjo;

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

public enum OsType {

	OS(null),
		Windows(OS),
			WindowsNT(Windows),
				WindowsNTWorkstation(WindowsNT),
				WindowsNTServer(WindowsNT),
			Windows2000(Windows),
				Windows2000Server(Windows2000),
				Windows2000Workstation(Windows2000),
			WindowsXp(Windows) {
				@Override
				public boolean major() {
					return true;
				}
			},
			WindowsVista(Windows),
			Windows7(Windows),
			Windows95(Windows),
			Windows98(Windows),
		Unix(OS) {
				@Override
				public boolean supportsXWindowSystem() {
					return true;
				}
			},
			Linux(Unix) {
				@Override
				public boolean major() {
					return true;
				}
			},
			AIX(Unix),
			HpUx(Unix),
			SunOs(Unix),
	;

	private final OsType parent;
	private final List<OsType> children = new ArrayList<OsType>();
	private final List<OsType> allChildren = new ArrayList<OsType>();

	OsType (OsType parent) {
		this.parent = parent;
		if (parent != null) {
			parent.addChild(this);
		}
	}

	public OsType parent() {
		return parent;
	}

	public boolean is(OsType other) {
		if (other == null) {
			return false;
		}

		for (OsType osType = this; osType != null; osType = osType.parent()) {
			if (other == osType) {
				return true;
			}
		}
		return false;
	}

	public List<? extends OsType> children() {
		return Collections.unmodifiableList(children);
	}

	public List<? extends OsType> allChildren() {
		return Collections.unmodifiableList(allChildren);
	}

	private void addChild(OsType child) {
		this.children.add(child);

		List<OsType> greatChildren = new ArrayList<OsType>();
		greatChildren.add(child);
		greatChildren.addAll(child.allChildren());

		OsType currentAncestor = this;
		while (currentAncestor != null) {
			currentAncestor.allChildren.addAll(greatChildren);
			currentAncestor = currentAncestor.parent;
		}
	}

	public boolean supportsXWindowSystem() {
		if (parent == null) {
			return false;
		}

		return parent.supportsXWindowSystem();
	}

	public boolean major() {
		if (parent == null) {
			return false;
		}

		return parent.major();
	}
}