Java, 400
Java is blessed (?) with many Exception
s and Error
s. There are many Exception
s that are specific to the operation of a single class. As an example of one of the most extreme cases, there are more than 10 Exception
s (all are subclass of IllegalFormatException
) dedicated to Formatter
class alone, and I have taken time to make the code throws (almost) all of them.
My current answer features 40 different Exception
s/Error
s, and they randomly get executed depending on the modulo of System.nanoTime()
with some integer.
This method can only be used to measure elapsed time and is not related to any other notion of system or wall-clock time. The value returned represents nanoseconds since some fixed but arbitrary origin time (perhaps in the future, so values may be negative). The same origin is used by all invocations of this method in an instance of a Java virtual machine; other virtual machine instances are likely to use a different origin.
The method above should be allowed, since it falls into case "3. Cannot use the number of tics or cpu cycles, unless they are counted relatively to the start of the main program thread".
Compilation Instruction
Oracle's JRE/JDK or OpenJDK is strongly recommended for running the code. Otherwise, some Exception may not be thrown, since some of them relies on the internal details of the reference implementation and I don't have a reliable fall-back.
The code below compiles successfully with javac 1.7.0_11
and produces all Exceptions on java 1.7.0_51
.
To run this code, you need to copy and paste the code below to a Unicode aware editor (e.g. Notepad++), save it in UTF-16 (Big-Endian or Little-Endian doesn't matter as long as the BOM is written).
Change working directory (cd
) to where the source code is saved (this is important).
Compile the code with the following command:
javac G19115.java -encoding "UTF-16"
And run the code:
java G19115
There is nothing destructive in my code, since I also want to test run it on my computer. The most "dangerous" code is deleting ToBeRemoved.class
file in the current folder. Other than that, the rest doesn't touch the file system or the network.
import java.util.*;
import java.util.regex.*;
import java.lang.reflect.*;
import java.text.*;
import java.io.*;
import java.nio.*;
import java.nio.charset.*;
import java.security.*;
class G19115 {
// The documentation says System.nanoTime() does not return actual time, but a relative
// time to some fixed origin.
private static int n = (int) ((System.nanoTime() % 40) + 40) % 40;
@SuppressWarnings("deprecation")
public static void main(String args[]) {
/**
* If the code is stated to be a bug, then it is only guaranteed to throw Exception on
* Oracle's JVM (or OpenJDK). Even if you are running Oracle's JVM, there is no
* guarantee it will throw Exception in all future releases future either (since bugs
* might be fixed, classes might be reimplemented, and an asteroid might hit the earth,
* in order from the least likely to most likely).
*/
System.out.println(n);
switch (n) {
case 0:
// Bug JDK-7080302
// https://bugs.openjdk.java.net/browse/JDK-7080302
// PatternSyntaxException
System.out.println(Pattern.compile("a(\u0041\u0301\u0328)", Pattern.CANON_EQ));
System.out.println(Pattern.compile("öö", Pattern.CANON_EQ));
// Leave this boring pattern here just in case
System.out.println(Pattern.compile("??+*"));
break;
case 1:
// Bug JDK-6984178
// https://bugs.openjdk.java.net/browse/JDK-6984178
// StringIndexOutOfBoundsException
System.out.println(new String(new char[42]).matches("(?:(?=(\\2|^))(?=(\\2\\3|^.))(?=(\\1))\\2)+."));
// Leave this boring code here just in case
System.out.println("".charAt(1));
break;
case 2:
// IllegalArgumentException
// Bug JDK-8035975
// https://bugs.openjdk.java.net/browse/JDK-8035975
// Should throw IllegalArgumentException... by documentation, but does not!
System.out.println(Pattern.compile("pattern", 0xFFFFFFFF));
// One that actually throws IllegalArgumentException
System.out.println(new SimpleDateFormat("Nothing to see here"));
break;
case 3:
// Bug JDK-6337993 (and many others...)
// https://bugs.openjdk.java.net/browse/JDK-6337993
// StackOverflowError
StringBuffer buf = new StringBuffer(2000);
for (int i = 0; i < 1000; i++) {
buf.append("xy");
}
System.out.println(buf.toString().matches("(x|y)*"));
// Leave this boring code here just in case
main(args);
break;
case 4:
// NumberFormatException
String in4 = "123\r\n";
Matcher m4 = Pattern.compile("^\\d+$").matcher(in4);
if (m4.find()) {
System.out.println(Integer.parseInt(in4));
} else {
System.out.println("Bad input");
}
// NotABug(TM) StatusByDesign(TM)
// $ by default can match just before final trailing newline character in Java
// This is why matches() should be used, or we can call m.group() to get the string matched
break;
case 5:
// IllegalStateException
String in5 = "123 345 678 901";
Matcher m5 = Pattern.compile("\\d+").matcher(in5);
System.out.println(m5.group(0));
// The Matcher doesn't start matching the string by itself...
break;
case 6:
// ArrayIndexOutOfBoundsException
// Who is the culprit?
String[] in6 = {
"Nice weather today. Perfect for a stroll along the beach.",
" Mmmy keeyboaardd iisss bbrokkkkeeen ..",
"",
"\t\t\t \n\n"};
for (String s: in6) {
System.out.println("First token: " + s.split("\\s+")[0]);
}
// Culprit is "\t\t\t \n\n"
// String.split() returns array length 1 with empty string if input is empty string
// array length 0 if input is non-empty and all characters match the regex
break;
case 7:
// ConcurrentModificationException
List<Integer> l7 = testRandom(42);
Integer prev = null;
// Remove duplicate numbers from the list
for (Integer i7: l7) {
if (prev == null) {
prev = i7;
} else {
if (i7.equals(prev)) {
l7.remove(i7);
}
}
}
System.out.println(l7);
// This is one of the typical mistakes that Java newbies run into
break;
case 8:
// ArithmeticException
// Integer division by 0 seems to be the only way to trigger this exception?
System.out.println(0/0);
break;
case 9:
// ExceptionInInitializerError
// Thrown when there is an Exception raised during initialization of the class
// What Exception will be thrown here?
Static s9 = null;
System.out.println(s9.k);
// A bit less interesting
Static ss9 = new Static();
// ----
// A class is only initialized when any of its method/field is
// used for the first time (directly or indirectly)
// Below code won't throw Exception, since we never access its fields or methods
// Static s;
// OR
// Static s = null;
break;
case 10:
// BufferOverflowException
short s10 = 20000;
ShortBuffer b10 = ShortBuffer.allocate(0).put(s10);
// Boring stuff...
break;
case 11:
// BufferUnderflowException
ShortBuffer.allocate(0).get();
// Another boring stuff...
break;
case 12:
// InvalidMarkException
ShortBuffer.allocate(0).reset();
// Boring stuff again...
// reset() cannot be called if mark() is not called before
break;
case 13:
// IndexOutOfBoundsException
System.out.println("I lost $m dollars".replaceAll("[$]m\\b", "$2"));
// $ needs to be escaped in replacement string, since it is special
break;
case 14:
// ClassCastException
Class c14 = Character.class;
for (Field f: c14.getFields()) {
System.out.println(f);
try {
int o = (int) f.get(c14);
// If the result is of primitive type, it is boxed before returning
// Check implementation of sun.reflect.UnsafeStaticIntegerFieldAccessorImpl
System.out.println(o);
} catch (IllegalAccessException e) {
e.printStackTrace();
}
}
break;
case 15:
// NoSuchElementException
List<Integer> l15 = new ArrayList<Integer>();
Iterator i = l15.iterator();
System.out.println(i.next());
// Another boring one...
break;
case 16:
// ArrayStoreException
Object x[] = new String[3];
x[0] = new Integer(0);
// Straight from the documentation
// I don't even know that this exists...
break;
case 17:
// IllegalThreadStateException
Thread t17 = new Thread();
t17.start();
t17.setDaemon(true);
// setDaemon can only be called when the thread has not started or has died
break;
case 18:
// EmptyStackException
Stack<Integer> s18 = new Stack<Integer>();
s18.addAll(testRandom(43));
while (s18.pop() != null);
// Originally ThreadDeath, which works when running from Dr. Java but not when
// running on cmd line. Seems that Dr. Java provides its own version of
// Thread.UncaughtExceptionHandler that prints out ThreadDeath.
// Please make do with this boring Exception
break;
case 19:
// NegativeArraySizeException
Array.newInstance(Integer.TYPE, -1);
// Do they have to create such a specific Exception?
break;
case 20:
// OutOfMemoryError
Array.newInstance(Integer.TYPE, 1000, 1000, 1000, 1000);
break;
case 21:
// UnsupportedCharsetException
// UCS-2 is superseded by UTF-16
Charset cs21 = Charset.forName("UCS-2");
CharsetEncoder ce21 = cs21.newEncoder();
// Just in case...
cs21 = Charset.forName("o_O");
// "o_O" is a (syntactically) valid charset name, so it throws UnsupportedCharsetException
break;
case 22:
// IllegalCharsetNameException
boolean isSupported;
isSupported = Charset.isSupported("o_O");
isSupported = Charset.isSupported("+_+");
Charset cs22 = Charset.forName("MerryChristmas!Hohoho!");
// This is getting stupid...
break;
case 23:
// NoClassDefFoundError
File f = new File("ToBeRemoved.class");
f.delete();
ToBeRemoved o23 = new ToBeRemoved();
// This shows that class is loaded on demand
break;
case 24:
// InputMismatchException
Scanner sc = new Scanner("2987654321");
sc.nextInt();
// Out of range
break;
case 25:
// Formatter class has many RuntimeException defined
// DuplicateFormatFlagsException
System.out.printf("%0000000000000000000000000000000000000000000000000005%d\n", 42);
break;
case 26:
// FormatFlagsConversionMismatchException
System.out.printf("%,d\n", Integer.MAX_VALUE);
System.out.printf("%,x\n", Integer.MAX_VALUE);
// Thousand separator is only applicable to base 10
System.out.printf("%(5.4f\n", Math.PI);
System.out.printf("%(5.4f\n", -Math.PI);
System.out.printf("%(5.4a\n", -Math.PI);
// '(' flag is used to surround negative value with "( )" instead of prefixing with '-'
// '(' can't be used with conversion 'a'
break;
case 27:
// IllegalFormatCodePointException
System.out.printf("%c", Character.MAX_CODE_POINT + 1);
// Larger than current Unicode maximum code point (0x10FFFF)
break;
case 28:
// IllegalFormatConversionException
String i28 = "0";
System.out.printf("%d", i28);
// A boring example
break;
case 29:
// IllegalFormatFlagsException
System.out.printf("% d\n", Integer.MAX_VALUE);
System.out.printf("% d\n", Integer.MIN_VALUE);
System.out.printf("%+d\n", Integer.MAX_VALUE);
System.out.printf("%+d\n", Integer.MIN_VALUE);
System.out.printf("% +d\n", Integer.MIN_VALUE);
// Use either ' ' or '+ ' flag, not both, since they are mutually exclusive
break;
case 30:
// IllegalFormatPrecisionException
System.out.printf("%5.4f\n", Math.PI);
System.out.printf("%5.4a\n", Math.PI);
System.out.printf("%5.4x\n", Math.PI);
// Precision does not apply to 'x', which is integer hexadecimal conversion
// To print a floating point number in hexadecimal, use conversion 'a'
break;
case 31:
// IllegalFormatWidthException
System.out.printf("%3n");
// For conversion n, width is not supported
break;
case 32:
// MissingFormatArgumentException
System.out.printf("%s\n%<s", "Pointing to previous argument\n");
System.out.printf("%<s", "Pointing to previous argument");
// No previous argument
break;
case 33:
// MissingFormatWidthException
System.out.printf("%5d %<d\n", 42); // Pad left
System.out.printf("%-5d %<d\n", 42); // Pad right
System.out.printf("%-d\n", 42);
// Missing width
break;
case 34:
// UnknownFormatConversionException
System.out.printf("%q", "Shouldn't work");
// No format conversion %q
// UnknownFormatFlagsException cannot be thrown by Formatter class in
// Oracle's implementation, since the flags have been checked in the regex
// used to recognize the format string
break;
case 35:
// IllformedLocaleException
System.out.printf(new Locale("ja"), "%tA %<tB %<tD %<tT %<tZ %<tY\n", new Date());
System.out.printf(new Locale.Builder().setLanguage("ja").setScript("JA").setRegion("JA").build(), "%tA %<tB %<tD %<tT %<tZ %<tf\n", new Date());
// Thrown by Locale.Builder.setScript()
break;
case 36:
// NullPointerException
Pattern p36 = Pattern.compile("a(b)?c");
Matcher m36 = p36.matcher("ac");
if (m36.find()) {
for (int i36 = 0; i36 <= m36.groupCount(); i36++) {
// Use Matcher#end(num) - Matcher#start(num) for length instead
System.out.printf("%3d [%d]: %s\n", i36, m36.group(i36).length(), m36.group(i36));
}
}
break;
case 37:
// AccessControlException
System.setSecurityManager(new SecurityManager());
System.setSecurityManager(new SecurityManager());
break;
case 38:
// SecurityException
// Implementation-dependent
Class ϲlass = Class.class;
Constructor[] constructors = ϲlass.getDeclaredConstructors();
for (Constructor constructor: constructors) {
constructor.setAccessible(true);
try {
Class Сlass = (Class) constructor.newInstance();
} catch (Throwable e) {
System.out.println(e.getMessage());
}
// The code should reach here without any Exception... right?
}
// It is obvious once you run the code
// There are very few ways to get SecurityException (and not one of its subclasses)
// This is one of the ways
break;
case 39:
// UnknownFormatFlagsException
// Implementation-dependent
try {
System.out.printf("%=d", "20");
} catch (Exception e) {
// Just to show the original Exception
System.out.println(e.getClass());
}
Class classFormatter = Formatter.class;
Field[] fs39 = classFormatter.getDeclaredFields();
boolean patternFound = false;
for (Field f39: fs39) {
if (Pattern.class.isAssignableFrom(f39.getType())) {
f39.setAccessible(true);
// Add = to the list of flags
try {
f39.set(classFormatter, Pattern.compile("%(\\d+\\$)?([-#+ 0,(\\<=]*)?(\\d+)?(\\.\\d+)?([tT])?([a-zA-Z%])"));
} catch (IllegalAccessException e) {
System.out.println(e.getMessage());
}
patternFound = true;
}
}
if (patternFound) {
System.out.printf("%=d", "20");
}
// As discussed before UnknownFormatFlagsException cannot be thrown by Oracle's
// current implementation. The reflection code above add = to the list of flags
// to be parsed to enable the path to the UnknownFormatFlagsException.
break;
}
}
/*
* This method is used to check whether all numbers under d are generated when we call
* new Object().hashCode() % d.
*
* However, hashCode() is later replaced by System.nanoTime(), since it got stuck at
* some values when the JVM is stopped and restarted every time (running on command line).
*/
private static List<Integer> testRandom(int d) {
List<Integer> k = new ArrayList<Integer>();
for (int i = 0; i < 250; i++) {
k.add(new Object().hashCode() % d);
}
Collections.sort(k);
System.out.println(k);
return k;
}
}
class ToBeRemoved {};
class Static {
static public int k = 0;
static {
System.out.println(0/0);
}
}
List of Exceptions and Errors
In order as declared in switch-case statement. There are 37 Exception
s and 3 Error
s in total.
- PatternSyntaxException (via bug in
Pattern
, with boring case as backup)
- StringIndexOutOfBoundsException (via bug in
Pattern
, with boring case as backup)
- IllegalArgumentException (helps me find a bug in
Pattern
, with boring case as backup)
- StackOverflowError (via recursive implementation in
Pattern
, with boring case as backup)
- NumberFormatException (shows that
$
in Pattern
can match before final line terminator)
- IllegalStateException (via accessing matched groups in
Matcher
without performing a match)
- ArrayIndexOutOfBoundsException (shows confusing behavior of
split(String regex)
)
- ConcurrentModificationException (via modifying a Collection during a for-each loop)
- ArithmeticException (via integer division by 0)
- ExceptionInInitializerError (via causing
Exception
during initialization of a class)
- BufferOverflowException (
java.nio.*
-specific Exception
)
- BufferUnderflowException (
java.nio.*
-specific Exception
)
- InvalidMarkException (
java.nio.*
-specific Exception
)
- IndexOutOfBoundsException (via reference to non-existent capturing group in replacement)
- ClassCastException
- NoSuchElementException
- ArrayStoreException
- IllegalThreadStateException
- EmptyStackException (
java.util.Stack
-specific Exception
)
- NegativeArraySizeException
- OutOfMemoryError (via boring allocation of big array)
- UnsupportedCharsetException
- IllegalCharsetNameException (shows when
Charset.isSupported(String name)
returns false or throws Exception
)
- NoClassDefFoundError (shows that classes are loaded on first access to method/constructor or field)
- InputMismatchException (
java.util.Scanner
-specific Exception
)
- DuplicateFormatFlagsException (from here to 35 are
java.util.Formatter
-specific Exception
s)
- FormatFlagsConversionMismatchException (with interesting example of format syntax)
- IllegalFormatCodePointException
- IllegalFormatConversionException
- IllegalFormatFlagsException
- IllegalFormatPrecisionException
- IllegalFormatWidthException
- MissingFormatArgumentException (with interesting example of format syntax)
- MissingFormatWidthException
- UnknownFormatConversionException
- IllformedLocaleException
- NullPointerException
- AccessControlException (shows that the default
SecurityManager
is usable)
- SecurityException (via invoking constructor of
Class
class)
- UnknownFormatFlagsException (shows that this
Exception
can't be thrown in Oracle's implementation, no backup)
Is generating a guid considered as random? – microbian – 11 years ago
Good question. I think entropy needs to be achieved magically (house of cards code) and not artificially so I would say no to GUID's. – ja72 – 11 years ago
For JS - is crashing browsers counted as 25 bonus or not? Can I choose which browser my code should be tested on? – eithed – 11 years ago
Crashing the host (browser or framework) awards the 25 bonus points. It must always crash though. – ja72 – 11 years ago
The problem is to write a non-deterministic function without using non-deterministic means (excluding clock too). C is one of the languages that gives you access to uninitialized pointer references. So the solutions I am seeing are based on uninitialized pointers. To me using uninitialized pointers is as good (or bad) as using a guid or random method. – microbian – 11 years ago
Point taken. Although unitialized variables/pointers are a source of pleanty of insane software so I think this stands. But can one answer the challenge with managed code? – ja72 – 11 years ago
@ja72 What if I have managed code that somehow obtains a memory address (specifically, the address of a dynamically allocated array)? Would it be a valid response if I used that information to cause nondeterministic behavior? – H2CO3 – 11 years ago
@H2CO3 - sure, that's the spirit of insanity. – ja72 – 11 years ago
@ja72 Excellent, in this case, see my answer -- using my own language :) – H2CO3 – 11 years ago