Java Class Popularity

Taken from a heap dump of a JBoss Application Server with some applications deployed, i've look at the number of objects in the heap and compiled a 'popularity list' accordingly:

java.util
1. ArrayList
2. HashMap
3. TreeMap
4. Vector
5. Hashtable
6. LinkedList
7. HashSet
8. WeakHashMap
9. TreeSet

Read on to see the full list. I've marked some classes which I find interesting enough to have a second look on them. Know your library.

10. LinkedHashMap
11. Properties
12. Stack - Use Dequeue instead
13. BitSet
14. LinkedHashSet
15. EnumMap
16. IdentityHashMap

java.lang
1. String
2. Long
3. Class
4. Double
5. Integer
6. Byte
7. Short
8. StringBuffer
9. ThreadLocal
10. Character
11. Float

java.lang.ref
1. SoftReference - Use for caches.
2. WeakReference
3. ReferenceQueue
4. FinalReference
5. PhantomReference

java.lang.reflect
1. Method
2. Constructor
3. Field
4. Type

java.util.concurrent
1. ConcurrentHashMap
2. TimeUnit
3. LinkedBlockingQueue
4. ThreadPoolExecutor
5. CopyOnWriteArrayList - Warning!

java.util.concurrent.atomic
1. AtomicLong - For sequence counters
2. AtomicInteger
3. AtomicBoolean

java.util.concurrent.locks
1. ReentrantLock - Yeah, with getHoldCount()

java.math
1. BigDecimal
2. BigInteger
3. RoundingMode
4. MutableBigInteger (Not public API)
5. SignedMutableBigInteger (Not public API)

java.nio
1. DirectByteBuffer
2. HeapByteBuffer

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