public class Singleton{
private static final Singleton singleton;
private Singleton(){
}
public static final synchronized Singleton getInstance(){
if(singleton==null){
singleton=new Singleton();
}
return singleton;
}
}
双重检查锁:线程安全,根据需求使用
public class Singleton{
private volatile static Singleton singleton;
private Singleton(){
}
public static final Singleton getInstance(){
if(singleton==null){
synchronized(Singleton.class){
if(singleton==null){
singleton=new Singleton();
}
}
}
return singleton;
}
}
静态内部类锁:线程安全,比较推荐
public class Singleton{
private Singleton(){
}
private static class Holder{
public static final Singleton singleton=new Singleton();
}
public static final Single getInstance(){
return Holder.singleton;
}
}
饿汗式:线程安全,但没有实现懒加载
public class Singleton{
private static final Singleton singleton=new Singleton();
private Singleton(){
}
public static final Singleton getInstance(){
return singleton;
}
}
枚举:线程安全,但比较少人用
public class Singleton{
public enum EasySingleton{
INSTANCE;
}
}