This presentation is about the best practices of Java code optimization, optimization of multiple threads synchronization, optimization of garbage collection process and more. This presentation by Andrii Antilikatorov (Lead Software Engineer, GlobalLogic) was delivered at GlobalLogic Java Conference in Krakow on December 12, 2015.

1. ©2015 GlobalLogic Inc.

2. 2
Java Performance Boost
by Andrii Antilikatorov

3. 3

4. 4
Optimize or not optimize?

5. 5
Strings & Primitive types
Use String.concat() for 2 params

6. 6
Avoid usage byte[] to String constructor (Java 6)
• Update to Java 7 or later
• Minimize usage of constructor

7. 7
String Pooling
String
String
String
String
String
String
String
String
String
String
StringString
Do not use String.intern() on Java 6
Pooling is efficient on Java 7 and above
Works great in multithreaded code
JVM string pool is NOT thread local

8. 8
String Deduplication
String
String
String
String
String
String
String
String
String
String
StringString
Available from Java 8 update 20
Requires G1 collector to be
enabled. Optional phase of G1.
Unlikely to run on the loaded systems
Processes only strings that survived
after few garbage collections
Doesn’t mean you shouldn’t use
pooling

9. 9
Understanding of “switch on String”

10. 10
Avoid heavy logic in static constructors

11. 11
Maps & Sets - Adding/removing elements
Set:
Map:

12. 12
Performance of Date/Time entities
24 bytes 448 bytes
java.util.Date java.util.GregorianCalendar

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14. 14
Synchronized block or synchronized method?
0: aload_0
1: getfield
2: nop
3: iconst_m1
4: ireturn
0: aload_0
1: dup
2: astore_1
3: monitorenter
4: aload_0
5: getfield
6: nop
7: iconst_m1
8: aload_1
9: monitorexit
10: ireturn
11: astore_2
12: aload_1
13: monitorexit
14: aload_2
15: athrow

15. 15
Thread-safe variant of ArrayList
Manual synchronization of
operations with ArrayList
Use CopyOnWriteArrayList -
thread-safe variant of Array
List

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Synchronized or volatile variables?
Volatile variables are less expensive than synchronized
Volatile are thread-safe for atomic operations
Volatile acquires lock on variable, therefore not thread-safe
for non-atomic operations

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Additional memory-saving techniques
Make all your inner classes static by default
Prefer a BitSet to arrays/lists of Boolean
Use memory-efficient storages for tiny collections

18. ©2015 GlobalLogic Inc.
Thank you!