JavaBlock — release any Java objects created during evaluation once evaluation finishes

BeginJavaBlock, EndJavaBlock — mark the beginning and end of a Java block

KeepJavaObject — allow a Java object to persist when the current JavaBlock ends

ReleaseJavaObject — finish using a Java object in the Wolfram Language

SameObjectQ — whether two JavaObject expressions reference the same Java object

LoadedJavaObjects, LoadedJavaClasses — list all Java objects or classes in use