What is an OutOfMemoryError exception, and how can I produce it?

Question

For a homework exercise involving exception handling, I need to produce an OutOfMemoryError exception so I can write a try-catch and catch it:

"13.10 (OutOfMemoryError) Write a program that causes the JVM to throw an OutOfMemoryError and catches and handles this error."

I searched the Java API and couldn't find anything on OutOfMemoryError exceptions in the exception list. What is an OutOfMemoryError exception, and how can I produce one for my assignment?

What did you find out about OOMEs when you searched for them? — Dave Newton, Mar 22 '12 at 00:10
How to find Java API information on OutOfMemoryError: Go to the [API Docs](http://docs.oracle.com/javase/6/docs/api/index.html), press Ctrl+F, type in OutOfMemoryError, and press enter. — Mike Clark, Mar 22 '12 at 00:10
Put an international crap-load of objects inside a collection - do this in a loop - and bingo - OOM. — Java42, Mar 22 '12 at 00:11
There's a number of ways to write a program that _throws_ the exception (doing something with an array would probably be your best bet), but I'm not sure about **catching** it... — Clockwork-Muse, Mar 22 '12 at 00:14
@X-Zero: catching is not the problem, but actually *handling* it might be. — Niklas B., Mar 22 '12 at 00:17
@Mike: I heard some superior browsers support this very new and shiny feature called "incremental search", so simply pressing Ctrl+F and typing "OutOfM" might actually be enough! — Niklas B., Mar 22 '12 at 02:14
This question appears to be off-topic because it is answered by the documentation. — user207421, Feb 05 '14 at 09:31

score 5 · Answer 1 · answered Mar 22 '12 at 00:17

5

Much simpler (and guaranteed to work) than creating millions of objects:

public static void throwOomE() {
    throw new well, you can just search for the rest of the answer
}

answered Mar 22 '12 at 00:17

Voo

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I was just about to suggest this, +1 – Jeffrey Mar 22 '12 at 00:19

Niklas B. · Answer 2 · 2012-03-22T00:24:57.070

4

The easiest way I can think of:

for (String x = "x";; x += x);

You might want to get a bit creative to crash it even faster.

edited Mar 22 '12 at 00:24

answered Mar 22 '12 at 00:11

Niklas B.

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Before you wrote "for(;;) {x = x + 1}" What does writing a for loop in that way mean? Also, thanks!" – Zolani13 Mar 22 '12 at 01:03
@Zolani: `for(;;)` is an infinite loop. – Niklas B. Mar 22 '12 at 01:03

score 3 · Answer 3 · answered Mar 22 '12 at 00:12

3

Much like I do with every java related question, the first thing I did was google:

java 6 <class-name>

In other words:

java 6 OutOfMemoryError

I got this informative link as the first result:

http://docs.oracle.com/javase/6/docs/api/java/lang/OutOfMemoryError.html

answered Mar 22 '12 at 00:12

jahroy

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Let me yahoo that for you... – jahroy Mar 22 '12 at 00:51

score 3 · Accepted Answer · answered Mar 22 '12 at 00:14

OutOfMemoryError is thrown when the JVM can't allocate enough memory to complete the requested action.

To produce these just allocate a bunch of memory in a loop or something similar, but remember to keep your already allocated objects, preferably in a ArrayList or something, or else the garbage collector might reuse the space and free up some memory.

Something like

ArrayList<Object> list = new ArrayList<Object>();

try {
    while ( true )
        list.add( new Object() );
} catch ( OutOfMemoryError e ) {
    // And we are done...
}

You might want to replace Object with a class that takes up some considerable amount of space, or else this might take some time.

Reference: http://docs.oracle.com/javase/1.4.2/docs/api/java/lang/OutOfMemoryError.html

score 3 · Answer 5 · answered Mar 22 '12 at 03:04

3

My favorite way to do this is.

byte[] crasher = new byte[Integer.MAX_VALUE];

answered Mar 22 '12 at 03:04

Shawn Shroyer

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score 1 · Answer 6 · answered Mar 22 '12 at 00:12

An OutOfMemoryError is thrown by the VM when it runs out of memory for allocating new objects. Thus you can cause this exception to hapen when you create too many objects.

To do so, start creating objects that will not be collected by the garbage collector (for example, link them to each other) in an infinite loop -- the VM will eventually run out of free memory for the next object to be allocated, throwing the exception. When you catch it, be careful though as you won't be able to do much -- the VM does not have (much) memory left for any operations.

score 1 · Answer 7 · answered Mar 22 '12 at 00:21

OutOfMemoryException appears when your heap contains no free space for new objects. Also you should persist references for objects somewhere, otherwise garbage colector takes care about they.

Binary crash (needed amount of bytes doubled on each iteration :)

String x = "1";
while (true){
    x = (x + x);
}

** read all references for better understanding

What is an OutOfMemoryError exception, and how can I produce it?

7 Answers7