Name: rlT66838 Date: 08/14/97


PROBLEM DESCRIPTION:
The small program included below fails with a NoClassDefFoundError.
It creates 60 threads that each create a RandomAccessFile.
If the program creates only 20 Threads (20 RandomAccessFile),
for example, then there is no NoClassDefFoundError.
Apparently RandomAccessFile is corrupting program memory.
 
In a much larger version of this program the NoClassDefFoundError
occurs after "new RandomAccessFile" is called the 30th time.
Also, in the much larger program the 30th RandomAccessFile call
fails with an IOException.

SYSTEM INFO: SunOS 5.5.1 Generic_103640-08 sun4u sparc SUNW,Ultra-2
 
BUILD INSTRUCTIONS:
Create a separate build area and copy the following source files to it:
        Churn.java
        ChurnEvent.java
        ChurnThread.java
 
I ran "jdk1.1.3/bin/javac *.java" to build my Churn program
 
Run "jdk1.1.3/bin/java Churn" to create 60 files and see the output below.

OUTPUT of Churn:
Thread Thread-4 creates filenumber 0
Thread Thread-5 creates filenumber 1
java.lang.IllegalArgumentException: mode must be r or rw
Thread Thread-6 creates filenumber 2
Thread Thread-7 creates filenumber 3
Thread Thread-8 creates filenumber 4
Thread Thread-9 creates filenumber 5
Thread Thread-10 creates filenumber 6
Thread Thread-11 creates filenumber 7
Thread Thread-12 creates filenumber 8
Thread Thread-13 creates filenumber 9
Thread Thread-14 creates filenumber 10
Thread Thread-15 creates filenumber 11
Thread Thread-16 creates filenumber 12
Thread Thread-17 creates filenumber 13
Thread Thread-18 creates filenumber 14
Thread Thread-19 creates filenumber 15
Thread Thread-20 creates filenumber 16
Thread Thread-21 creates filenumber 17
Thread Thread-22 creates filenumber 18
Thread Thread-23 creates filenumber 19
Thread Thread-24 creates filenumber 20
Thread Thread-25 creates filenumber 21
Thread Thread-26 creates filenumber 22
Thread Thread-27 creates filenumber 23
Thread Thread-28 creates filenumber 24
Thread Thread-29 creates filenumber 25
Thread Thread-30 creates filenumber 26
Thread Thread-31 creates filenumber 27
Thread Thread-32 creates filenumber 28
Thread Thread-33 creates filenumber 29
Thread Thread-34 creates filenumber 30
Thread Thread-35 creates filenumber 31
Thread Thread-36 creates filenumber 32
Thread Thread-37 creates filenumber 33
Thread Thread-38 creates filenumber 34
Thread Thread-39 creates filenumber 35
Thread Thread-40 creates filenumber 36
Thread Thread-41 creates filenumber 37
Thread Thread-42 creates filenumber 38
Thread Thread-43 creates filenumber 39
Thread Thread-44 creates filenumber 40
Thread Thread-45 creates filenumber 41
Thread Thread-46 creates filenumber 42
Thread Thread-47 creates filenumber 43
Thread Thread-48 creates filenumber 44
Thread Thread-49 creates filenumber 45
Thread Thread-50 creates filenumber 46
Thread Thread-51 creates filenumber 47
Thread Thread-52 creates filenumber 48
Thread Thread-53 creates filenumber 49
Thread Thread-54 creates filenumber 50
Thread Thread-55 creates filenumber 51
Thread Thread-56 creates filenumber 52
Thread Thread-57 creates filenumber 53
Thread Thread-58 creates filenumber 54
Thread Thread-59 creates filenumber 55
Thread Thread-60 creates filenumber 56
Thread Thread-61 creates filenumber 57
Thread Thread-62 creates filenumber 58
Thread Thread-63 creates filenumber 59
java.lang.NoClassDefFoundError: ChurnEvent
        at Churn.run(Churn.java:30)
        at Churn.main(Churn.java:12)

CHURN SOURCE:

public class Churn implements Runnable {
 
    private ChurnThread churnThread[];
 
    public Churn()
    {
    }
 
    public static void main(String args[])
    {
        Churn churn = new Churn();
        churn.run();
    }
 
    public void run()
    {
        // Create 60 threads that each create a RandomAccessFile
        churnThread = new ChurnThread[60];
 
        for (int i = 0; i < churnThread.length; i++) {
           churnThread[i] = new ChurnThread(i);
        }
 
        for (int i = 0; i < churnThread.length; i++) {
                churnThread[i].start();
                Thread.yield();
        }
 
        // Note that new Integer does not fail with NoClassDefFoundError.
        Integer myInteger = new Integer(0);
 
        // Note that new ChurnEvent (a class that is not extended) fails
        // with NoClassDefFoundError.
        ChurnEvent churnEvent = new ChurnEvent();
 
        try {
                Thread.sleep(10000);
        } catch(InterruptedException e) { ; }
 
        System.exit(0);
    }
}

import java.io.*;
class ChurnThread extends Thread
{
        RandomAccessFile churn_raf;
        int filenumber;
 
        public ChurnThread(int f)
        {
                filenumber = f;
        }
 
        public void run()
        {
            System.out.println("Thread " + Thread.currentThread().getName() + "
creates filenumber " + filenumber);
            if (filenumber == 1) {
                // Cause an exception to happen by constructing
                // a RandomAccessFile with a bad mode.
                // Actually, you don't even need to make an
                // IllegalArgumentException happen in order to see
                // the NoClassDefFoundError in thread named "main"
                // in this small version of a larger program.
                // The larger version of this program gets an
                // IOException the 30th time RandomAccessFile is
                // constructed. So it appears that the size of the
                // program determines when and how RandomAccessFile
                // corrupts the program's memory.
                try {
                        churn_raf = new
RandomAccessFile(Integer.toString(filenumber), "z");
                } catch (IOException e) {
                        System.out.println(e.toString());
                        stop();
                } catch (IllegalArgumentException e) {
                        System.out.println(e.toString());
                        stop();
                }
            } else {
                try {
                        churn_raf = new
RandomAccessFile(Integer.toString(filenumber), "rw");
                } catch (IOException e) {
                        stop();
                }
            }
 
            try {
                Thread.sleep(10000);
            } catch(InterruptedException e) { ; }
        }
}

class ChurnEvent
{
        public ChurnEvent()
        {
        }
}




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