"Comparison method violates its general contract!" - TimSort and GridLayout
I made a color palette with a jPanel and a JLabel array in it. At first it worked well, but then i put some other jLabels out of the JPanel and added them some events. Now I keep getting this error:
Exception in thread "AWT-EventQueue-0" java.lang.IllegalArgumentException: Comparison method violates its general contract!
at java.util.TimSort.mergeLo(TimSort.java:747)
at java.util.TimSort.mergeAt(TimSort.java:483)
at java.util.TimSort.mergeCollapse(TimSort.java:410)
at java.util.TimSort.sort(TimSort.java:214)
at java.util.TimSort.sort(TimSort.java:173)
at java.util.Arrays.sort(Arrays.java:659)
at java.util.Collections.sort(Collections.java:217)
at javax.swing.SortingFocusTraversalPolicy.enumerateAndSortCycle(SortingFocusTraversalPolicy.java:136)
at javax.swing.SortingFocusTraversalPolicy.getFocusTraversalCycle(SortingFocusTraversalPolicy.java:110)
at javax.swing.SortingFocusTraversalPolicy.getFirstComponent(SortingFocusTraversalPolicy.java:435)
at javax.swing.LayoutFocusTraversalPolicy.getFirstComponent(LayoutFocusTraversalPolicy.java:166)
at javax.swing.SortingFocusTraversalPolicy.getDefaultComponent(SortingFocusTraversalPolicy.java:515)
at java.awt.FocusTraversalPolicy.getInitialComponent(FocusTraversalPolicy.java:169)
at java.awt.DefaultKeyboardFocusManager.dispatchEvent(DefaultKeyboardFocusManager.java:380)
at java.awt.Component.dispatchEventImpl(Component.java:4731)
at java.awt.Container.dispatchEventImpl(Container.java:2287)
at java.awt.Window.dispatchEventImpl(Window.java:2719)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:723)
at java.awt.EventQueue.access$200(EventQueue.java:103)
at java.awt.EventQueue$3.run(EventQueue.java:682)
at java.awt.EventQueue$3.run(EventQueue.java:680)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.awt.EventQueue$4.run(EventQueue.java:696)
at java.awt.EventQueue$4.run(EventQueue.java:694)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:693)
at java.awt.SequencedEvent.dispatch(SequencedEvent.java:116)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:721)
at java.awt.EventQueue.access$200(EventQueue.java:103)
at java.awt.EventQueue$3.run(EventQueue.java:682)
at java.awt.EventQueue$3.run(EventQueue.java:680)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.awt.EventQueue$4.run(EventQueue.java:696)
at java.awt.EventQueue$4.run(EventQueue.java:694)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:693)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:244)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:163)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:151)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:147)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:139)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:97)
I tried to remove everything i've done after first time i got this error, but still keep getting it. When i change the layout from GridLayout to anything else, then the error disappears, but the code becomes useless. So i need GridLayout. When i move everything in that JPanel to another JPanel, the error also goes away. But when i remove the first JPanel, error comes back.
By the way, the program works, but it's not pleasent to keep getting errors...
Edit: When i use less than 225 color, there's no error. I'm really curious about what's happening. Any explanation would be appreciated...
It seems to me like you've hit a bug in the JDK since the error seems to come from Swing classes.
Options:
-
Define the property
java.util.Arrays.useLegacyMergeSortastrue. Either using in your code the lineSystem.setProperty("java.util.Arrays.useLegacyMergeSort", "true");before any Swing code. As the first line in the
mainmethod should work.Or adding
-Djava.util.Arrays.useLegacyMergeSort=trueto your starting options (in the console, or in the project properties in an IDE, Ant script, etc.)
Upgrade your JDK and see if the problem goes away
- Downgrade to Java 6
Report my findings:
-Djava.util.Arrays.useLegacyMergeSort=true
works
but
System.setProperty("java.util.Arrays.useLegacyMergeSort", "true");
does not work.
It is due to the fact that in JDK Arrays.class
static final class LegacyMergeSort {
private static final boolean userRequested = ...
It is a static variable which is defined when jvm starts. Setting System property in the program will have no effect if the class has been loaded into jvm.
I have beeing monitoring the LegacyMergeSort.userRequested variable, and the findings confirmed with above statement.
Update: The program must set system properties before java.util.Arrays is loaded to classloader. Otherwise, once it is loaded, setting the properties is not going to be useful due to the reason mentioned above.
Make sure nothing else loaded Arrays.class:
By putting following code to your program to test:
java.lang.reflect.Method m = ClassLoader.class.getDeclaredMethod("findLoadedClass", new Class[] { String.class });
m.setAccessible(true);
ClassLoader cl = ClassLoader.getSystemClassLoader();
Object test1 = m.invoke(cl, "java.util.Arrays");
System.out.println("test1 loaded? ->" + (test1 != null));
[Update] This solution unfortunately is not guaranteed to solve the problem in all cases. It is not enough to patch the default SortingFocusTraversalPolicy of the KeyboardFocusManager.
I recommend to read the answer by Robin Loxley below, including his Update. [/Update]
java.lang.IllegalArgumentException: Comparison method violates its general contract!
at java.util.TimSort.mergeHi(TimSort.java:868)
This problem is caused by a bug in javax.swing.LayoutComparator.
The following class installs a fixed version of javax.swing.LayoutComparator, which does not violate the contract of Comparator<Component>. This (or any other) fixed version of javax.swing.LayoutComparator should be submitted to Oracle by some Oracle contributor.
package ...;
import java.awt.Component;
import java.awt.ComponentOrientation;
import java.awt.FocusTraversalPolicy;
import java.awt.KeyboardFocusManager;
import java.awt.Window;
import java.lang.reflect.Field;
import java.util.Comparator;
import java.util.LinkedList;
import java.util.ListIterator;
import javax.swing.JRootPane;
import javax.swing.SortingFocusTraversalPolicy;
import javax.swing.UIManager;
/**
* Uses reflection to install a fixed version of {@link javax.swing.LayoutComparator} to solve the
* LayoutFocusTraversalPolicy/TimSort problem.
*
* <p>
* <code>java.lang.IllegalArgumentException: Comparison method violates its general contract!</code>
* <br/>
* {@code at java.util.TimSort.mergeHi(TimSort.java:868)}
* </p>
* <p>
* Usage: call {@code Class.forName(LayoutFocusTraversalPolicyTimSortBugFixer.class.getName())}
* before creating Swing components.
* </p>
*
* @author Burkhard Strauss
* @since Feb 2015
*/
public class LayoutFocusTraversalPolicyTimSortBugFixer
{
static
{
UIManager.getUI(new JRootPane()); // make Swing install the SortingFocusTraversalPolicy
final KeyboardFocusManager keyboardFocusManager = KeyboardFocusManager
.getCurrentKeyboardFocusManager();
final FocusTraversalPolicy focusTraversalPolicy = keyboardFocusManager
.getDefaultFocusTraversalPolicy();
boolean fixed = false;
if (focusTraversalPolicy instanceof SortingFocusTraversalPolicy)
{
try
{
final Field field = SortingFocusTraversalPolicy.class.getDeclaredField("comparator");
final boolean accessible = field.isAccessible();
try
{
field.setAccessible(true);
field.set(focusTraversalPolicy, new LayoutComparator());
fixed = true;
}
finally
{
field.setAccessible(accessible);
}
}
catch (final Exception e)
{
}
}
if (!fixed)
{
Loggers.getLoggerFor(LayoutFocusTraversalPolicyTimSortBugFixer.class).warn("could not fix the bug");
}
}
/**
* Fixed version of {@link javax.swing.LayoutComparator}.
* <p>
* Search for 'bugfix' in the code.
* </p>
*
* @author Burkhard Strauss
* @since Feb 2015
*/
@SuppressWarnings("serial")
private static class LayoutComparator implements Comparator<Component>, java.io.Serializable
{
private static final int ROW_TOLERANCE = 10;
private boolean horizontal = true;
private boolean leftToRight = true;
@SuppressWarnings("unused")
void setComponentOrientation(final ComponentOrientation orientation)
{
horizontal = orientation.isHorizontal();
leftToRight = orientation.isLeftToRight();
}
@Override
public int compare(Component a, Component b)
{
if (a == b)
{
return 0;
}
// Row/Column algorithm only applies to siblings. If 'a' and 'b'
// aren't siblings, then we need to find their most inferior
// ancestors which share a parent. Compute the ancestory lists for
// each Component and then search from the Window down until the
// hierarchy branches.
if (a.getParent() != b.getParent())
{
final LinkedList<Component> aAncestory = new LinkedList<Component>();
for (; a != null; a = a.getParent())
{
aAncestory.add(a);
if (a instanceof Window)
{
break;
}
}
if (a == null)
{
// 'a' is not part of a Window hierarchy. Can't cope.
throw new ClassCastException();
}
final LinkedList<Component> bAncestory = new LinkedList<Component>();
for (; b != null; b = b.getParent())
{
bAncestory.add(b);
if (b instanceof Window)
{
break;
}
}
if (b == null)
{
// 'b' is not part of a Window hierarchy. Can't cope.
throw new ClassCastException();
}
for (ListIterator<Component> aIter = aAncestory.listIterator(aAncestory.size()), bIter = bAncestory
.listIterator(bAncestory.size());;)
{
if (aIter.hasPrevious())
{
a = aIter.previous();
}
else
{
// a is an ancestor of b
return -1;
}
if (bIter.hasPrevious())
{
b = bIter.previous();
}
else
{
// b is an ancestor of a
return 1;
}
if (a != b)
{
break;
}
}
}
final int ax = a.getX(), ay = a.getY(), bx = b.getX(), by = b.getY();
int zOrder = a.getParent().getComponentZOrder(a) - b.getParent().getComponentZOrder(b);
{
//
// Here is the bugfix:
// Don't return 0 if a != b. This would violate the contract of
// Comparator<Component>.compare().
//
if (zOrder == 0)
{
zOrder = -1;
}
}
if (horizontal)
{
if (leftToRight)
{
// LT - Western Europe (optional for Japanese, Chinese, Korean)
if (Math.abs(ay - by) < ROW_TOLERANCE)
{
return (ax < bx) ? -1 : ((ax > bx) ? 1 : zOrder);
}
else
{
return (ay < by) ? -1 : 1;
}
}
else
{ // !leftToRight
// RT - Middle East (Arabic, Hebrew)
if (Math.abs(ay - by) < ROW_TOLERANCE)
{
return (ax > bx) ? -1 : ((ax < bx) ? 1 : zOrder);
}
else
{
return (ay < by) ? -1 : 1;
}
}
}
else
{ // !horizontal
if (leftToRight)
{
// TL - Mongolian
if (Math.abs(ax - bx) < ROW_TOLERANCE)
{
return (ay < by) ? -1 : ((ay > by) ? 1 : zOrder);
}
else
{
return (ax < bx) ? -1 : 1;
}
}
else
{ // !leftToRight
// TR - Japanese, Chinese, Korean
if (Math.abs(ax - bx) < ROW_TOLERANCE)
{
return (ay < by) ? -1 : ((ay > by) ? 1 : zOrder);
}
else
{
return (ax > bx) ? -1 : 1;
}
}
}
}
}
}
I just ran into the same error and spent a good amount of time tracking it down. To help others who run into this error it is important to know how to test TimSort. The checks that violate the transitivity contract and throw this error are deep in the algorithm and require a test to meet certain criteria before this problem can be reproduced.
- Create a list with 32 or more objects.
- Within that list, there needs to two or more runs.
- Each run must contain 3 or more objects.
Once you meet those two criteria you can begin testing for this failure.
A run is defined as a sub-set of the list where each item is already in the desired ordered state.