Programming Groovy 2

4.5 Using Closures for Resource Cleanup

Java’s automatic garbage collection is a mixed blessing. We don’t have to worry about resource deallocation, provided we release references. But there’s no guarantee of when the resource will actually be cleaned up, because it’s at the discretion of the garbage collector. In certain situations, we might want the cleanup to happen straightaway. This is the reason we see methods such as ​close​ and ​destroy​ on resource-intensive classes.

One problem, though, is that the users of our class may forget to call these methods. Closures can help ensure that the methods get called. In the following code we create a ​FileWriter​ and write some data, but ignore the call to ​close​ on it. If we run this code, the ...