单例工厂

public abstract class Human {
    public abstract void doSomething();
}

public class WhiteHuman extends Human {
    @Override
    public void doSomething() {
    }
}

public class YellowHuman  extends Human {
    @Override
    public void doSomething() {
    }
}

public class Factory {
    private static final Map<String,Object> objectMap = new HashMap<String, Object>();
    
    public synchronized static <T extends Human> T createHuman(Class<T> c){
        Human human = null;
        String className = null;
        className =c.getName();
        try {
            if (!objectMap.containsKey(className)) {
                Class class1 = Class.forName(className);
                Constructor constructor = class1.getDeclaredConstructor();
                constructor.setAccessible(true);
                human = (Human) constructor.newInstance();
                objectMap.put(className, human);
            }
        } catch (Exception e) {
            // TODO: handle exception
        }
        return (T)objectMap.get(className);
    } 
}

//测试
public class Demo {
    public static  void main(String[] s) {
        for(int i = 0; i < 100; i++){
            System.out.println(Factory.createHuman(YellowHuman.class));
        }
    }
}