# java -version
java version "1.4.0"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.0-b92)
Java HotSpot(TM) Client VM (build 1.4.0-b92, mixed mode)
# swap -s (before running java)
total: 10176k bytes allocated + 2400k reserved = 12576k used, 840288k available
# more nothing.java
import java.io.*;
import java.lang.Thread;
public class nothing
{
  public static void main(String[] args)
  {
    try
    {
      while ( true )
      {
        java.lang.Thread.sleep( 1000 );
        System.out.print(".");
      }
    }
    catch ( java.lang.InterruptedException e ) { }
  }
}
# java nothing
.......

another window# ps -eo pid,pcpu,vsz,args | grep java
  263 1.5 52256 java nothing
  264 0.0 1000 grep java
 # swap -s (after starting java...)
total: 17592k bytes allocated + 9008k reserved = 26600k used, 825336k available



From this example, 52MB is memory is necessary to run "nothing".