This section provides a tutorial example on generating the java.lang.OutOfMemoryError exception by allocating a big array in a loop.
I wrote the following program to try to push JVM for more memory in a loop:
/**
* MemoryCrash.java
* Copyright (c) 2002 by Dr. Herong Yang, herongyang.com
*/
class MemoryCrash {
public static void main(String[] a) {
int max = 100;
Runtime rt = Runtime.getRuntime();
Object[] arr = new Object[max];
for (int n=0; n<max; n++) {
System.out.println("Having "+n*10+" MB and adding 10 MB...");
arr[n] = new long[10*1024*128];
System.out.println(" Free memory: " + rt.freeMemory());
System.out.println("Total memory: " + rt.totalMemory());
try {
Thread.sleep(2*1000);
} catch (InterruptedException e) {
System.out.println("Interreupted...");
}
}
}
}
Output on HotSpot Client 1.6.0 VM with -Xms2m -Xmx64m
C:\>\progra~1\java\jdk1.6.0_02\bin\java -Xms2m -Xmx64m
MemoryCrash
Having 0 MB and adding 10 MB...
Free memory: 1907072
Total memory: 12521472
Having 10 MB and adding 10 MB...
Free memory: 8421336
Total memory: 29528064
Having 20 MB and adding 10 MB...
Free memory: 6210456
Total memory: 37826560
Having 30 MB and adding 10 MB...
Free memory: 14484288
Total memory: 56606720
Having 40 MB and adding 10 MB...
Free memory: 3998512
Total memory: 56606720
Having 50 MB and adding 10 MB...
Exception in thread "main" java.lang.OutOfMemoryError:
Java heap space at MemoryCrash.main(MemoryCrash.java:12)
Output on HotSpot Client 1.4.0 VM with -Xms2m -Xmx64m
Having 0 MB and adding 10 MB...
Free memory: 1897344
Total memory: 12521472
Having 10 MB and adding 10 MB...
Free memory: 8463216
Total memory: 29573120
Having 20 MB and adding 10 MB...
Free memory: 6275936
Total memory: 37871616
Having 30 MB and adding 10 MB...
Free memory: 14644240
Total memory: 56725504
Having 40 MB and adding 10 MB...
Free memory: 4157184
Total memory: 56725504
Having 50 MB and adding 10 MB...
Exception in thread "main" java.lang.OutOfMemoryError
Output on JRockit 7.0 JVM with -Xms2m -Xmx64m
Having 0 MB and adding 10 MB...
Free memory: 8717040
Total memory: 19419136
Having 10 MB and adding 10 MB...
Free memory: 8698800
Total memory: 29904896
Having 20 MB and adding 10 MB...
Free memory: 7607344
Total memory: 39297024
Having 30 MB and adding 10 MB...
Free memory: 6951960
Total memory: 49127424
Having 40 MB and adding 10 MB...
Free memory: 6558720
Total memory: 59219968
Having 50 MB and adding 10 MB...
java.lang.OutOfMemoryError
Note that
My 10MB array is slightly more than 10MB because of the array overhead.
I also tested with JRockit with -Xmx512m, it got 200MB before running
out of memory. My system has: 128MB physical memory, and 288MB paging file
size.
