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Sorting 1 billion integers using collections.sort() gives out of memory error

I'm trying to sort a list of 1 billion integers using Collection.sort(List) and it throws following exception
"Exception in thread "main" java.lang.OutOfMemoryError: Java heap space"
-xms is set as 512m and xmx at 1536m. How do i sort it? I've 8GB ram in my system so allocating more physical memory is not a problem. I tried giving -xmx 2048m but vm could not initialize with that setting.

It's likely case-sensitive and there should be no space, try with -Xmx2048m.
Nonstandard Options
-Xmxn
Specifies the maximum size, in bytes, of the memory allocation pool. This value must a multiple of 1024 greater than 2 MB. Append the letter k or K to indicate kilobytes, or m or M to indicate megabytes. The default value is chosen at runtime based on system configuration.
For server deployments, -Xms and -Xmx are often set to the same value. See Garbage Collector Ergonomics at
http://docs.oracle.com/javase/7/docs/technotes/guides/vm/gc-ergonomics.html
Examples:
-Xmx83886080
-Xmx81920k
-Xmx80m
See docs.

I tried giving -xmx 2048m but vm could not initialize with that setting.
You are likely using a 32-bit JVM, which have a practical max heap size below 2GB. You should try a 64-bit JVM.
Note also that you should set the VM parameters for the program, not for Eclipse (as it seems you are doing per one of your comments). You do that by selecting the dropdown menu in Run then Run Configurations. Then select your program and open the Arguments panel.

Java Invalid Maximum Heap Size for Windows Remote Desktop

I am running a Java application on a windows server (32-bit, 12GB RAM) with the
-Xmx8g and I am getting an error saying
Invalid Maximum Heap Size.
The specified size exceeds the maximum representable size.
But the same application is running on my local machine (64-bit, win-7, 6GB RAM) with the same -Xmx8g command.
I dont have the option of changing the OS of the server. Is there any possible solution to this?

With 32-bit-windows the adress-space cannot be larger than 4GB. By default half of this is reserved for the OS, so the maximum memory available for the JVM is 2GB. Reserve some for stack and other native memory and the maximum heap-size will end up with about 1.5GB.
Using the /3G-switch for windows might increase that limit by 1GB (as it limits the OS-storage to 1GB), but that is all that is the maximum that's possible in a 32-bit OS (and with a 32-bit JVM in general).

will java use more memory when running on machine with larger ram

If I have a smaller-ram machine and a larger-ram machine. I run the same java code on them.
Will jvm do garbage collection more lazily on the machine with larger ram?
The problem I am trying to solve is an out of memory issue. People reported that they have Out of memory issue on small ram machine. I want to test that but the only machine I have now has a much larger ram than theirs. I am wondering if I do the test on this larger-ram machine and keep track of the memory usage, will the memory usage be the same on a smaller-ram machine or it will use even less memory?
Thanks!
Erben

You need to take a look at the JVM memory parameters. actually you can set the as much memory as you want to your JVM :
-Xmx2048m -> this param to set the max memory that the JVM can allocate
-Xms1024m -> the init memory that JVM will allocate on the start up
-XX:MaxPermSize=512M -> this for the max Permanent Generation memory
so in your case you can set the much memory as in the another machine. so you machine will not take more RAM than the Xmx value
and you may want to check this parameters also.
-XX:MaxNewSize= -> this need to be 40% from your Xmx value
-XX:NewSize=614m -> this need to be 40% from your Xmx value
also you may tell you JVM what type of GC to use like :
-XX:+UseConcMarkSweepGC
SO if you set this parameters in the both machines, you will get the same results and the same GC activity most likely.

Yes it will. This depends on the default maximum heap size. You can check your current maximum heap size using this command:
java -XshowSettings:vm
On my wife's laptop (Windows 8.1, 4 GB RAM, 32-Bit-Java-Runtime) it is 247.5 MB, while on my laptop (Windows 7, 8 GB RAM, 64-Bit-Java-Runtime) it is 903.12 MB.
This is determined by Java (see https://stackoverflow.com/a/4667635/3236102, though the values shown there are for server-class-machines, they might be different from normal machines).
If you want your vm to simulate a low-RAM-machine just use the -Xmx flag to limit your machine to less RAM (e.g. -Xmx128m for 128 MB RAM allocation).
The best thing might be to ask the users that encounter the Out Of Memory-issues to check their maximum heap size (using the command above) and set your machine to the same maximum heap size, so you have the same conditions as they have.

The issue can be reproduced with larger RAM.
First you need to get the heap size configuration from the people who reported the issue.
Use the same heap size to reproduce the issue.
Use below jvm params for heap settings.
-Xmx512m Max heap memory that is used to store objects
-XX:MaxPermSize=64m Max perm gen size. This space is used to store meta info like loaded classes etc

Is there a upper limit to how much heap size JUnits can use

My Jenkins build is running out of memory because of JUnits. When I try to give it (the JUnits) more than 4GB it errors out. I am using Linux as my build machine.
Invalid maximum heap size: -Xmx4096m
I am just wondering, is there a upper limit to how much heap size JUnits can use?

"For a 32-bit process model, the maximum virtual address size of the process is typically 4 GB, though some operating systems limit this to 2 GB or 3 GB. The maximum heap size is typically -Xmx3800m (1600m) for 2 GB limits), though the actual limitation is application dependent. For 64-bit process models, the maximum is essentially unlimited."
Found a pretty good answer here:
Java maximum memory on Windows XP

Memory is allocated to JVM not JUnit or any other class.
and there is limit on 32-bit system to assign max of 4Gb but if you requires more memory then move to 64 bit machine as there is no limit of max memory allocation .

i would guess you are using a 32 bit jvm ..
check this post:
Maximum Java heap size of a 32-bit JVM on a 64-bit OS

It's not JUnit but JVM. 4GB heap is too much for 32-bit JVMs.

Avoiding Initial Memory Heap Size Error

I run a Java code with the following command:
$ java -Xms4G -Xmx4G myjavacode
My cpu's RAM capacity is 6GB.
However it always fail to execute giving me this
error message:
Invalid initial heap size: -Xms5G
The specified size exceeds the maximum representable size.
Could not create the Java virtual machine
Is there any way to set up Java option so that we can
execute the code?

You've exceeded the maximum heap size of your JVM. This is both JVM and OS dependent. In most 32-bit systems the maximum value will be 2Gb, regardless of the physical memory available.

By default Java will run in 32 bit mode. Be sure to give it the -d64 option to put it into 64 bit mode. Once in 64-bit mode, you shouldn't have any trouble allocating a 6GB JVM.

Actually, the maximum memory size on 32-bit systems can vary, being anything up to 4 GB, but 2 GB is a common value. It's often possible to re-link your kernel to increase this to 3 or 3.5 GB. The issue, of course, is that you just don't have the address space to map more memory. Have you tried a 64-bit machine?
Also, remember to set your ulimit higher before you do this.