【代码积累】replace constructor with factory

最新推荐文章于 2023-03-24 10:14:47 发布

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最新推荐文章于 2023-03-24 10:14:47 发布

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本文展示了一个使用Java实现的单例工厂模式示例代码，该工厂类利用`ConcurrentHashMap`来注册并管理对象实例。通过静态方法`getInstance()`获取工厂实例，并提供创建指定类型对象的方法`createSpecifiedVehicle()`。

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import java.util.concurrent.ConcurrentHashMap;


public class Factory {
	private ConcurrentHashMap<String, Object> registedList = new ConcurrentHashMap<String, Object>();
	public void register(String name,Object object) {
		registedList.put(name, object);
	}
	
	private static Factory factory = null;
	
	public Vehicle createSpecifiedVehicle(String name) {
		return ((Vehicle)registedList.get(name)).createObject();
		/*This is not gonna work as when createSpecifiedVehicle is called the static blocks in sub-classes has not been 
		 * executed yet so registedList is actually empty.Static block in a class will be executed at the time the class
		 * is being load,and only when the class is needed it will be loaded by ClassLoader.*/
	}
	
	public static Factory getInstance() {
		if( null == factory ) {
			synchronized(Factory.class) {
				if( null == factory ) {
					factory = new Factory();
				}
			}
		}
		
		return factory;
	}
}