将对象引用设置为null或调用finalize（）方法？

Question

As a java beginner I wanted to ask about if I should set an object reference to null, or call the finalize method in a large project?

For example,

while( obj... some code here){
 //code stuff
}
obj = null; // or obj.finalize();

Since im done with the obj and there are no more references to it what should i do with it? set it to null or call finalize();?

I read the java doc but this paragraph The finalize method is never invoked more than once by a Java virtual machine for any given object. confused me. Does that mean that even if i use it, it won't do anything at all unless GC decides to do so? Then, will my decision to set the obj to null help any?

This all assuming its a large project and the scope has yet to end in order for GC to deallocate it itself. Thanks.

Answer 1

Neither. If obj is no longer used further in the code (and nothing else references the same object as obj does), the object will no longer be reachable and will become a candidate for Garbage Collection.

Setting obj to null will not achieve anything (YMMV depending on implementation of garbage collectors).

As for calling finalize() , don't. Let the Garbage Collector take care of that. But note that finalize is a method like any other. What the text you quoted is saying is that the GC will not call it more than once, regardless of the amount of times your code may have invoked it.

Answer 2

NEVER invoke an object's finalize() method manually. It is for the VM's use only. The VM will invoke it at an appropriate time (as part of the garbage collection process).

You may set a reference variable to null to possibly make an object eligible for garbage collection sooner than it otherwise would be, but doing so does not cause it to be GC'd immediately. (Note that you use the = operator for assignments; == is a relational operator for testing the equality of its operands.)

If your object maintains state that you must ensure is cleaned up on demand, then implement a different method for that. close() is a popular name for such methods. It is good practice to avoid implementing finalize() if at all possible. The GC will automatically take care of most resources that you might think you want to clean up manually in finalize() .