Java garbage collection

Garbage collection is the process of freeing storage that is used by objects that are no longer referred to by a program. With garbage collection, programmers no longer have to write error prone code to explicitly "free" or "delete" their objects. This code frequently results in "memory leak" program errors. The garbage collector automatically detects an object or group of objects that the user program can no longer reach. It does this because there are no references to that object in any program structure. Once the object has been collected, you can allocate the space for other uses.

The Java™ runtime environment includes a garbage collector that frees memory that is no longer in use. The garbage collector runs automatically, as needed.

The garbage collector can also be started explicitly under the control of the Java program using the java.lang.Runtime.gc() method.

• IBM Developer Kit for Java advanced garbage collection
  The IBM^® Developer Kit for Java implements an advanced garbage collector algorithm. This algorithm allows the discovery and collection of unreachable objects without significant pauses in the operation of the Java program. A concurrent collector cooperatively discovers the references to objects under the running threads, instead of a single thread.
• Java garbage collection performance considerations
  Garbage collection on the iSeries™ Java virtual machine operates in a continuous asynchronous mode. The garbage collection-initial size (GCHINL) parameter on the Run Java (RUNJVA) command may affect application performance.