AppDomains that you unload by hand. I have not really experimented with this option.I was discussing this problem with a friend, who asserted that Java has the same problem.
To prove him wrong, I wrote the following class. You run it on the command line, passing an numeric argument that indicates the number of distinct classes you want to load. Try it out with and without the -Xnoclassgc option in Java!
import java.lang.Integer;
import java.lang.ClassLoader;
import java.lang.Class;
import java.lang.ClassNotFoundException;
public class ClassSFS {
public static void println(String s) {
System.out.println(s);
}
public static void println() {
System.out.println();
}
public static void print(String s) {
System.out.print(s);
}
public static void main(String[] args) {
println("Hello World");
int num_classes = Integer.parseInt(args[0]);
initbytes();
for(int i = 0; i < num_classes; i++) {
Tbytes[ 48 + 5 ] = (byte) (0x61 + (i/100) % 26);
Tbytes[ 48 + 6 ] = (byte) (0x61 + (i/10) % 26);
Tbytes[ 48 + 7 ] = (byte) (0x61 + (i/1) % 26);
CLoader cl = new CLoader();
try {
Class c = cl.findClass("T");
Object x = c.newInstance();
System.out.println("ClassLoader "+i+", x:"+x);
} catch (ClassNotFoundException e) {
System.out.println("ClassLoader "+i+", ClassNotFound e:"+e);
} catch (InstantiationException e) {
System.out.println("ClassLoader "+i+", InstantiationException e:"+e);
} catch (IllegalAccessException e) {
System.out.println("ClassLoader "+i+", IllegalAccessException e:"+e);
}
}
}
static class CLoader extends ClassLoader {
CLoader() { super(); }
public Class findClass(String name) throws ClassNotFoundException {
return
super.defineClass(name,
Tbytes,
0,
Tbytes.length);
}
}
private static int[] iTbytes = {
0xca, 0xfe, 0xba, 0xbe, 0x00, 0x00, 0x00, 0x2e, 0x00, 0x20, 0x0a, 0x00, 0x0a, 0x00, 0x16, 0x07,
0x00, 0x17, 0x0a, 0x00, 0x02, 0x00, 0x16, 0x08, 0x00, 0x18, 0x0a, 0x00, 0x02, 0x00, 0x19, 0x09,
0x00, 0x09, 0x00, 0x1a, 0x0a, 0x00, 0x02, 0x00, 0x1b, 0x08, 0x00, 0x0b, 0x07, 0x00, 0x1c, 0x07,
/* f e e */
0x00, 0x1d, 0x01, 0x00, 0x03, 0x66, 0x65, 0x65, 0x01, 0x00, 0x12, 0x4c, 0x6a, 0x61, 0x76, 0x61,
0x2f, 0x6c, 0x61, 0x6e, 0x67, 0x2f, 0x53, 0x74, 0x72, 0x69, 0x6e, 0x67, 0x3b, 0x01, 0x00, 0x06,
0x3c, 0x69, 0x6e, 0x69, 0x74, 0x3e, 0x01, 0x00, 0x03, 0x28, 0x29, 0x56, 0x01, 0x00, 0x04, 0x43,
0x6f, 0x64, 0x65, 0x01, 0x00, 0x0f, 0x4c, 0x69, 0x6e, 0x65, 0x4e, 0x75, 0x6d, 0x62, 0x65, 0x72,
0x54, 0x61, 0x62, 0x6c, 0x65, 0x01, 0x00, 0x08, 0x74, 0x6f, 0x53, 0x74, 0x72, 0x69, 0x6e, 0x67,
0x01, 0x00, 0x14, 0x28, 0x29, 0x4c, 0x6a, 0x61, 0x76, 0x61, 0x2f, 0x6c, 0x61, 0x6e, 0x67, 0x2f,
0x53, 0x74, 0x72, 0x69, 0x6e, 0x67, 0x3b, 0x01, 0x00, 0x08, 0x3c, 0x63, 0x6c, 0x69, 0x6e, 0x69,
0x74, 0x3e, 0x01, 0x00, 0x0a, 0x53, 0x6f, 0x75, 0x72, 0x63, 0x65, 0x46, 0x69, 0x6c, 0x65, 0x01,
0x00, 0x06, 0x54, 0x2e, 0x6a, 0x61, 0x76, 0x61, 0x0c, 0x00, 0x0d, 0x00, 0x0e, 0x01, 0x00, 0x16,
0x6a, 0x61, 0x76, 0x61, 0x2f, 0x6c, 0x61, 0x6e, 0x67, 0x2f, 0x53, 0x74, 0x72, 0x69, 0x6e, 0x67,
0x42, 0x75, 0x66, 0x66, 0x65, 0x72, 0x01, 0x00, 0x03, 0x54, 0x3c, 0x3e, 0x0c, 0x00, 0x1e, 0x00,
0x1f, 0x0c, 0x00, 0x0b, 0x00, 0x0c, 0x0c, 0x00, 0x11, 0x00, 0x12, 0x01, 0x00, 0x01, 0x54, 0x01,
0x00, 0x10, 0x6a, 0x61, 0x76, 0x61, 0x2f, 0x6c, 0x61, 0x6e, 0x67, 0x2f, 0x4f, 0x62, 0x6a, 0x65,
0x63, 0x74, 0x01, 0x00, 0x06, 0x61, 0x70, 0x70, 0x65, 0x6e, 0x64, 0x01, 0x00, 0x2c, 0x28, 0x4c,
0x6a, 0x61, 0x76, 0x61, 0x2f, 0x6c, 0x61, 0x6e, 0x67, 0x2f, 0x53, 0x74, 0x72, 0x69, 0x6e, 0x67,
0x3b, 0x29, 0x4c, 0x6a, 0x61, 0x76, 0x61, 0x2f, 0x6c, 0x61, 0x6e, 0x67, 0x2f, 0x53, 0x74, 0x72,
0x69, 0x6e, 0x67, 0x42, 0x75, 0x66, 0x66, 0x65, 0x72, 0x3b, 0x00, 0x21, 0x00, 0x09, 0x00, 0x0a,
0x00, 0x00, 0x00, 0x01, 0x00, 0x0a, 0x00, 0x0b, 0x00, 0x0c, 0x00, 0x00, 0x00, 0x03, 0x00, 0x01,
0x00, 0x0d, 0x00, 0x0e, 0x00, 0x01, 0x00, 0x0f, 0x00, 0x00, 0x00, 0x1d, 0x00, 0x01, 0x00, 0x01,
0x00, 0x00, 0x00, 0x05, 0x2a, 0xb7, 0x00, 0x01, 0xb1, 0x00, 0x00, 0x00, 0x01, 0x00, 0x10, 0x00,
0x00, 0x00, 0x06, 0x00, 0x01, 0x00, 0x00, 0x00, 0x01, 0x00, 0x01, 0x00, 0x11, 0x00, 0x12, 0x00,
0x01, 0x00, 0x0f, 0x00, 0x00, 0x00, 0x2e, 0x00, 0x02, 0x00, 0x01, 0x00, 0x00, 0x00, 0x16, 0xbb,
0x00, 0x02, 0x59, 0xb7, 0x00, 0x03, 0x12, 0x04, 0xb6, 0x00, 0x05, 0xb2, 0x00, 0x06, 0xb6, 0x00,
0x05, 0xb6, 0x00, 0x07, 0xb0, 0x00, 0x00, 0x00, 0x01, 0x00, 0x10, 0x00, 0x00, 0x00, 0x06, 0x00,
0x01, 0x00, 0x00, 0x00, 0x04, 0x00, 0x08, 0x00, 0x13, 0x00, 0x0e, 0x00, 0x01, 0x00, 0x0f, 0x00,
0x00, 0x00, 0x1e, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x06, 0x12, 0x08, 0xb3, 0x00, 0x06,
0xb1, 0x00, 0x00, 0x00, 0x01, 0x00, 0x10, 0x00, 0x00, 0x00, 0x06, 0x00, 0x01, 0x00, 0x00, 0x00,
0x02, 0x00, 0x01, 0x00, 0x14, 0x00, 0x00, 0x00, 0x02, 0x00, 0x15
};
private static byte[] Tbytes;
public static void initbytes()
{
Tbytes = new byte[ iTbytes.length ];
for(int i = 0; i < iTbytes.length; i++) {
Tbytes[i] = (byte)(iTbytes[i]);
}
print(""+nybble2char((Tbytes[0]>>4) & 0xF));
print(""+nybble2char((Tbytes[0]>>0) & 0xF));
print(""+nybble2char((Tbytes[1]>>4) & 0xF));
print(""+nybble2char((Tbytes[1]>>0) & 0xF));
print(""+nybble2char((Tbytes[2]>>4) & 0xF));
print(""+nybble2char((Tbytes[2]>>0) & 0xF));
print(""+nybble2char((Tbytes[3]>>4) & 0xF));
print(""+nybble2char((Tbytes[3]>>0) & 0xF));
println();
}
private static char nybble2char(int b) {
switch (b) {
case 0xf: return 'f';
case 0xe: return 'e';
case 0xd: return 'd';
case 0xc: return 'c';
case 0xb: return 'b';
case 0xa: return 'a';
default: return (char) (b+'a');
}
}
public static int Tcounter = 0;
}
The iTbytes array was generated by compiling
public class T { private static String fee = "fee"; public String toString() { return "T<>"+fee; }}, then loading the resulting class file into emacs, switching to hexl-mode, and doing some keyboard-macrology to convert it to something javac would accept.
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