Increasing Heap Size in Eclipse Example explains about how to set Heap Size in Eclipse and Avoiding OutOfMemoryError

There are 2 ways you can Increase Heap Size in  Eclipse

1) Change eclipse.ini (inside Eclipse folder)

-showsplash

org.eclipse.platform

--launcher.XXMaxPermSize

512m=========here change the size which you want

-vmargs

-Xms40m

-Xmx512m

-Xms setting the initial Java heap size

-Xmx setting the maximum Java heap size

you can change "-Xmx" setting to 1024m, It will increase the heap size of Eclipse

2) Insert Virtual Machine Values Into Your JRE

When Eclipse is started, 

• Open the Preferences ( For Mac: located under Eclipse menu item / For Windows: located under Window menu item )
• Inside the Java part, click Installed JREs,
• On the installed JRE being used (It may be jre5/6),
• Click Edit button, and add the following changed argument into the Default VM Arguments:

-Xms312M -Xmx512M