How come Eclipse compiles my project (automatically) without errors, but when I run Ant build.xml -> compile target, the build fails with compile error:

```
<MyClass> is not abstract and does not override abstract method <someMethod>

```

I understand this error message, but it seems not to be true, because 1) Eclipse shows no errors 2) Deploying this project to server succeeds and the class works as it should work.

So how is this problem even possible?