单例模式之懒汉式与饿汉式

单例模式：私有静态成员变量+私有构造方法+公有静态方法

饿汉式：当类被加载时就创建了该类的实例

public class BeanFactory {

private static BeanFactory beanFactory = new BeanFactory();

private BeanFactory(){
System.out.println("饿汉式");
}

public static BeanFactory getInstance(){
return beanFactory;
}
}

懒汉式：当用到该类时才会创建该类的实例

public class BeanFactory2 {

private static BeanFactory2 beanFactory = null;

private BeanFactory2(){
System.out.println("懒汉式");
}

public static BeanFactory2 getInstance(){
if(beanFactory == null){
beanFactory = new BeanFactory2();
}
return beanFactory;
}
}