1. Ali Bahu
11/26/2012
ECLIPSE MEMORY ANALYZER
(MAT)

2. INTRODUCTION
 The Java Garbage Collector releases Java objects from memory as
long as no other object refers to that object. A Java heap dump is an
image of the complete Java object graph at a certain point in time. It
includes all objects, Fields, Primitive types and object references. It is
possible to instruct the JVM to automatically create a heap dump in
case of a OutOfMemoryError.
 The Eclipse MAT helps to visualize (based on Java heap dumps) the
references to objects and provides tools to identify potential memory
leaks.
 It also helps with reduction in memory consumption. .

3. INTRODUCTION
 Eclipse MAT quickly analyzes:
 Productive heap dumps with hundreds of millions of objects
 Quickly calculates the retained sizes of objects,
 Checks who is preventing the Garbage Collector from collecting
objects
 Runs a report to automatically extract leak suspects.
 To tell the JVM to create a heapdump in case of an
OutOfMemoryError use the option:
-XX:+HeapDumpOnOutOfMemoryError

4. INSTALLATION
 Install Eclipse MAT via the Eclipse Update manager.
 Select "General Purpose Tools " and install:
 "Memory Analyser (Incubation)"
 "Memory Analyser (Charts)"

5. HOW TO USE ECLIPSE-MAT
 Create the Java project “com.fedex.test.first" and the package " com.fedex.test.first “
and Create the following class:
Package com.fedex.test.first;
import java.util.ArrayList;
import java.util.List;
public class Main
{
public static void main(String[] args)
{
List<String> list = new ArrayList<String>(); while (1<2)
{
list.add("OutOfMemoryError test");
} } }

6. RUN PROJECT
 In Eclipse add the -XX:+HeapDumpOnOutOfMemoryError to
the runtime configuration and run the project.

7. USING ECLIPSE-MAT
 You should get a new file in your project (.hprof).
 You may need to refresh your project (F5 on the project) if you are
unable to see the file.
 Double-click it and select
"Leak Suspects Report".

8. ANALYSIS
 Switch back to the overview and start your investigation of the heap
dump. The user interface is quite intuitive. Especially the dominator
tree gives a quick overview of the objects being used.
 You can also create a HeapDump via the jconsole. You can try that by
typing jconsole in the command line to start it.