兼顾性能和线程安全volatile \synchronized
public class LazyDoubleCheckSingleton {
private volatile static LazyDoubleCheckSingleton lazyDoubleCheckSingleton = null;
private LazyDoubleCheckSingleton(){
}
public static LazyDoubleCheckSingleton getInstance(){
if(lazyDoubleCheckSingleton == null){
synchronized (LazyDoubleCheckSingleton.class){
if(lazyDoubleCheckSingleton == null){
lazyDoubleCheckSingleton = new LazyDoubleCheckSingleton();
//1.分配内存给这个对象
// //3.设置lazyDoubleCheckSingleton 指向刚分配的内存地址
//2.初始化对象
// intra-thread semantics
// ---------------//3.设置lazyDoubleCheckSingleton 指向刚分配的内存地址
}
}
}
return lazyDoubleCheckSingleton;
}
}
单例Double Check
1、分配对象的内存空间
3、设置instance指向内存空间
2、初始化对象
4、初次访问对象
