In Eclipse IDE, if your program is consuming a lot of memory (loading big data) like this :

  List<Domain> list = domainBo.findAllDomain(100000);
  for(Domain domain : list){
	process(domain.getDomainName());

It can easily hit java.lang.OutOfMemoryError: Java heap space :

Exception in thread "main" java.lang.OutOfMemoryError: Java heap space
	at java.util.HashMap.<init>(HashMap.java:209)
	at java.util.LinkedHashMap.<init>(LinkedHashMap.java:181)

1. Solution – VM arguments

On Eclipse menu, clicks Run -> Run Configurations.., select the Java application you want to run, clicks on the Arguments tab, update the VM arguments with the following options

-Xms<size> - Set initial Java heap size
-Xmx<size> - Set maximum Java heap size

For example, -Xms512M -Xmx1024M

2. Mistake – eclipse.ini

The memory settings in eclipse.ini is allocated to Eclipse IDE only, not the program you want to run. A very common mistake is updated the heap size in eclipse.ini, and expects it to solve above out of memory problem.

But, if your Eclipse IDE is always crashed by no reason, you can try to increase the heap size and perm gen in eclipse.ini.

	
	-startu
	openFile
	-showsplash
        //...
	-XX:MaxPermSize=512m
	-Xms512m
	-Xmx1024m
        //...
	-Xdock:icon=../Resources/Eclipse.icns
	-XstartOnFirstThread

P.S eclipse.ini is located in the Eclipse installation folder.

References

1. FAQ How do I increase the permgen size available to Eclipse?
2. Find Out Your Java Heap Memory Size
3. Eclipse + Tomcat – Java.Lang.OutOfMemoryError: Java Heap Space