HotSpot GC algorithms overview

HotSpot JVM is implementing few algorithms for GC which are combined in few possible GC profiles.

Serial generational collector (-XX:+UseSerialGC).
Parallel for young space, serial for old space generational collector (-XX:+UseParallelGC).
Parallel young and old space generational collector (-XX:+UseParallelOldGC).
Concurrent mark sweep with serial young space collector (-XX:+UseConcMarkSweepGC
–XX:-UseParNewGC).
Concurrent mark sweep with parallel young space collector (-XX:+UseConcMarkSweepGC –XX:+UseParNewGC).
G1 garbage collector (-XX:+UseG1GC).
All profiles except G1 are using almost same young space collection algorithms (with serial vs parallel variations).