如何在Java中编写自己的垃圾收集器？

Question

This is most generally asked question in interview. I do not want to use Java garbage collector. How we can implement own garbage-collector functionality. Does anyone have solution for this question ?

Answer 1

From a practical perspective, this is not something that can really be done as the GC is an internal (and integral) part of the JVM. From an academic standpoint, you need to have a deep understanding of how the JVM allocates memory. Most garbage collection algorithms work by starting at some set of known roots. From each root, it traverses memory looking for any objects that no longer have any references to them. Those objects that don't have references are considered garbage and have the memory they occupy deallocated. Any remaining objects are still live and are moved around in memory to compact the memory usage and reduce fragmentation.

This is probably not precisely how the JVM GC works, but it illustrates the basic concepts.