Cannot allocate a java.lang.StringBuffer object with size of 1GB, not even
in 64-bit VM.

The problem is easily reproducible:

1. Testcase
-----------
% more Test.java
import java.io.*;

public class Test {

    public static void main(String argv[]) throws Exception {

        int size;
         size = 1073741824; // fails: 1GB
         size = 1073741800; // succeeds: 1GB-24
         size = 1073741808; // fails: 1GB-16
         size = 1073741804; // succeeds: 1GB-20
         size = 1073741805; // fails: 1GB-19

        Runtime runstats = Runtime.getRuntime();

        System.out.println("Max mem:" + runstats.maxMemory());
        System.out.println("Total mem:" + runstats.totalMemory());
        System.out.println("Free mem:" + runstats.freeMemory());

        System.out.println("Trying " + size );
        StringBuffer sb = new StringBuffer(size);
        System.out.println("StringBuffer of size: " + size + " allocated");

        System.out.println("Total mem:" + runstats.totalMemory());
        System.out.println("Free mem:" + runstats.freeMemory());
    }
}

%


2. Compile
----------
% /j2sdk1.4.2_05/bin/java -d64 -version
java version "1.4.2_05"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.2_05-b04)
Java HotSpot(TM) 64-Bit Server VM (build 1.4.2_05-b04, mixed mode)
%
% /j2sdk1.4.2_05/bin/javac Test.java
%


3. Run, trying 1GB
------------------
% /j2sdk1.4.2_05/bin/java -d64 -Xms4g -Xmx8g Test
Max mem:8505720832
Total mem:4252893184
Free mem:4252728928
Trying 1073741824
Exception in thread "main" java.lang.OutOfMemoryError
%


4. Trying almost 1GB (1GB-20B)
------------------------------

% /j2sdk1.4.2_05/bin/javac Test.java
% /j2sdk1.4.2_05/bin/java -d64 -Xms4g -Xmx8g Test
Max mem:8505720832
Total mem:4252893184
Free mem:4252728928
Trying 1073741804
StringBuffer of size: 1073741804 allocated
Total mem:4252958720
Free mem:2105352568
%


5. Java 1.5
-----------
% /jdk1.5.0/bin/java -d64 -version
java version "1.5.0-rc"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0-rc-b63)
Java HotSpot(TM) 64-Bit Server VM (build 1.5.0-rc-b63, mixed mode)
%
% /jdk1.5.0/bin/java -d64 -Xms4g -Xmx8g Test
Max mem:7635533824
Total mem:4116054016
Free mem:4094577848
Trying 1073741824
Exception in thread "main" java.lang.OutOfMemoryError: Requested array size exceeds VM limit
%


6. Documentation
----------------
 The API doc says, that argument is "int", which spans from -2GB to 2GB-1:

 StringBuffer(int length)
          Constructs a string buffer with no characters in it and an initial
          capacity specified by the length argument.

 No notice is given that there is a limit at about 1 GB.
###@###.### 10/21/04 17:28 GMT