FileLocations.java

package com.laytonsmith.PureUtilities;

import java.io.File;

/**
 * This class contains several constant file locations, which can be used
 * throughout the rest of the application. It also includes a static factory
 * method, which can be used to get the default class. Subclasses should be sure
 * to call the parent's static getter method, so that chaining will work properly
 * throughout the application. This particular class is agnostic to the application
 * itself, and so only provides generic locations that may be useful to most Java
 * applications. The controller for the application should use the most specific
 * subclass available when starting up the application, though classes themselves
 * should use as generic a class as possible when requesting file information.
 * Files are immutable, and likely are cached.
 */
public class FileLocations {
	
	private static FileLocations defaultInstance = null;
	
	private final static File USER_HOME;
	private final static File USER_DIR;
	private final static File JAVA_HOME;
	
	static {
		File userHome = null;
		File userDir = null;
		File javaHome = null;
		try{
			userHome = new File(System.getProperty("user.home"));
			userDir = new File(System.getProperty("user.dir"));
			javaHome = new File(System.getProperty("java.home"));
		} catch(SecurityException e){
			//This could happen in applets or some other wierd security configuration.
			//Regardless, we don't want this to ever fail.
		}
		USER_HOME = userHome;
		USER_DIR = userDir;
		JAVA_HOME = javaHome;
	}
	
	/**
	 * Returns the default FileLocations instance. If the controller
	 * has set a subclass, it will be returned, but by default it will be
	 * an instance of FileLocations.
	 * @return 
	 */
	public static FileLocations getDefault(){
		if(defaultInstance == null){
			defaultInstance = new FileLocations();
		}
		return defaultInstance;
	}
	
	/**
	 * Sets the default FileLocations provider.
	 * @param provider 
	 */
	public static void setDefault(FileLocations provider){
		defaultInstance = provider;
	}
	
	/**
	 * Returns the user's home directory.
	 * @return 
	 */
	public File getUserHome(){
		return USER_HOME;
	}
	
	/**
	 * Returns the user's working directory.
	 * @return 
	 */
	public File getUserDir(){
		return USER_DIR;
	}
	
	/**
	 * Returns the installation directory for the Java Runtime Environment (JRE).
	 * @return 
	 */
	public File getJavaHome(){
		return JAVA_HOME;
	}
}