Description Steve Jefferson 2005-05-26 06:24:40 EDT

It is possible to get TreeSet<T>.contains(T t) to throw an  
AbstractMethodError. This occurs on code compiled by Eclipse 3.1.M7 but not  
for code compiled by Sun 1.5.0_03 JDK. Can provide code for simple test case  
if required; however code is roughly as follows:  
1. Create an interface 'Thing' which extends Comparable<Thing>.  
2. Create an implementation of 'Thing', 'ThingImpl' say which provides an  
   an implementation of 'int compareTo(Thing t)'.  
3. Create (in a JUnit test case, say) a TreeSet<Thing>, create an instance of  
   ThingImpl and add to the TreeSet.  
4. Call 'contains()' on the TreeSet, passing the ThingImpl instance previously   
   added to the set. This should throw an AbstractMethodError with a stack   
   trace something like below. As stated previously, this does not occur with   
   code compiled under Sun JDK 1.5.0_03 but does on code compiled by Eclipse   
   3.1M7. Also occurs when running Eclipse-generated code under Sun JDK so   
   looks like an Eclipse compiler problem.  
  
java.lang.AbstractMethodError: ThingImpl.compareTo(Ljava/lang/Object;)I  
	at java.util.TreeMap.compare(TreeMap.java:1093)  
	at java.util.TreeMap.getEntry(TreeMap.java:347)  
	at java.util.TreeMap.containsKey(TreeMap.java:204)  
	at java.util.TreeSet.contains(TreeSet.java:196)  
	at ThingTest.testIt(ThingTest.java:24)  
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)  
	at  
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)  
	at  
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)  
	at java.lang.reflect.Method.invoke(Method.java:585)  
	at junit.framework.TestCase.runTest(TestCase.java:154)  
	at junit.framework.TestCase.runBare(TestCase.java:127)  
	at junit.framework.TestResult$1.protect(TestResult.java:106)  
	at junit.framework.TestResult.runProtected(TestResult.java:124)  
	at junit.framework.TestResult.run(TestResult.java:109)  
	at junit.framework.TestCase.run(TestCase.java:118)  
	at junit.framework.TestSuite.runTest(TestSuite.java:208)  
	at junit.framework.TestSuite.run(TestSuite.java:203)  
	at  
org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:474)  
	at  
org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:342)  
	at  
org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:194)