24 May 2017
1 分钟阅读
私有构造函数捕获模式私有构造函数捕获模式
《Java并发编程实践》的注解中有提到这一概念。
The private constructor exists to avoid the race condition that would occur if the copy constructor were implemented as this (p.x, p.y); this is an example of the private constructor capture idiom (Bloch and Gafter, 2005).
结合原文代码：
@ThreadSafe
public class SafePoint{
@GuardedBy("this") private int x,y;
private SafePoint (int [] a) { this (a[0], a[1]); }
public SafePoint(SafePoint p) { this (p.get()); }
public SafePoint(int x, int y){
this.x = x;
this.y = y;
}
public synchronized int[] get(){
return new int[] {x,y};
}
public synchronized void set(int x, int y){
this.x = x;
this.y = y;
}
}
这里的构造器public SafePoint(SafePoint p) { this (p.get()); }是为了捕获另一个实例的状态。get()方法是一个同步方法，为了避免竞态没有分别提供x、y的公有getter方法。
