一、懒汉式
public class LazySingleton
{
private static LazySingleton instance = null;
private LazySingleton()
{
}
public static synchronized LazySingleton getInstance()
{
if (instance == null)
{
instance = new LazySingleton();
}
return instance;
}
}二、饿汉式
public class EagerSingleton
{
private static EagerSingleton instance = new EagerSingleton();
private EagerSingleton()
{
}
public static EagerSingleton getInstance()
{
return instance;
}
}三、优化版（双重校验锁）
public class Singleton
{
private volatile static Singleton singleton = null;
private Singleton()
{
}
public static Singleton getSingleton()
{
if (singleton == null)
{
synchronized (Singleton.class)
{
if (singleton == null)
{
singleton = new Singleton();
}
}
}
return singleton;
}
}
