对象的序列化

package cn.cnic.lifx.singleton;

public class Singleton
{
private Singleton(){ }

private static class SingletonFactory
{
static Singleton instance = new Singleton();
}

public static Singleton getInstance()
{
return SingletonFactory.instance;
}
}

package cn.cnic.lifx.singleton;

public class Singleton2
{
private Singleton2(){ }

private static Singleton2 instance = new Singleton2();

public static Singleton2 getInstance()
{
return instance;
}
}

package cn.cnic.lifx.singleton;

public class Singleton3
{
private Singleton3(){ }

private static Singleton3 instance;

public synchronized static Singleton3 getInstance()
{
if(null == instance)
{
instance = new Singleton3();
}

return instance;
}
}