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Java Performance

Hands-on practice with thorough explanations, presentations, demos, small standalone exercises during the training.
A 3 days seminar for middle .NET developers

View Agenda

This training is for

Java developers who want to improve their abilities to tune-up the performance of their Java applications



Day 1

1. JVM runtime behavior

The “90/10” rule

  • Pause sources
  • Memory consumption

GC algorithms, main memory areas, etc

Chose the right GC policy for your application

JVM live tracing: see how and when the byte codes are transformed into machine code, GC activity, etc.

2. Profiling(hands-on)

Know the tools:

  • Built-in: jconsole, jvisualvm, jfr, jps, etc.
  • JProfiler

Real-time analysis

Generate and analyze heap dumps

Heap inspection, memory leaks detection, etc.

Profile a simple JPA application

Day 2

3. Programming techniques: how to optimize for performance. Some techniques presented here are bad; we consider and analyse them in order to see when they are worth using.

Reduce (e.g. StringBuffer instead of Strings for concatenation or scan problems)


  • Reuse buffers, flyweight pattern
  • Does flyweight really bring performance boost in heavily threaded applications?

Recycle: recycle objects, use ObjectPool

The cost of reflection

The cost of casts

Cache frequently computed values

  • Cache static and instance variables
  • Cached exceptions
  • Quick memcache intro

Weak references

4. JMM (Java Memory Model)

Building blocks

  • Examples and pitfalls
  • Data contention versus lock contention

Modern multi-threading constructs (hands-on)

  • Types of locks
  • Atomic DS
  • Executors, thread blocks
  • ConcurrentMap, BlockingQueue, BlockingDequeue
  • Future
  • COW data structures

Day 3

5. Smart” collections


Goldman Sachs Collections




6. Parallelism (with examples in Java 8)

Theory: map/reduce, scatter, gather, filter, etc.

Parallel map, parallel reduce, scan, histogram


Pitfalls (e.g. be careful at deadlocks): if the developer is not careful, he can call a blocking method from within a parallel stream.


7. JNI brief intro: write a small native utility (C code is given) and call it from Java.

Discuss main JNI architecture

JNI is sometimes useful: we will analyse these situations and see some real-life examples.


For the best experience we can offer, we will need details about each trainee:

  1. We assume the participants are already proficient in writing Java programs
  2. The operating system of your choice
  3. Your preferred IDE or editor
  4. If the system has at least 4GB of memory, the following should be installed on the host operating system: VirtualBox 4.3.x or later, Vagrant 1.7.x or later
  5. If the system has less than 4GB of memory: latest JDK 8 installed on the host operating system


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