This code:
***
class Bar extends Foo {
}
class Foo extends Bar {
}
***

causes this error:

java.lang.StackOverflowError
        at sun.tools.javac.SourceClass.basicCheck(SourceClass.java:430)
        at sun.tools.java.ClassDeclaration.getClassDefinition(ClassDeclaration.java:116)
        at sun.tools.javac.SourceClass.basicCheck(SourceClass.java:435)
        at sun.tools.java.ClassDeclaration.getClassDefinition(ClassDeclaration.java:116)
        at sun.tools.javac.SourceClass.basicCheck(SourceClass.java:435)
        at sun.tools.java.ClassDeclaration.getClassDefinition(ClassDeclaration.java:116)
        at sun.tools.javac.SourceClass.basicCheck(SourceClass.java:435)
        at sun.tools.java.ClassDeclaration.getClassDefinition(ClassDeclaration.java:116)
        at sun.tools.javac.SourceClass.basicCheck(SourceClass.java:435)
        at sun.tools.java.ClassDeclaration.getClassDefinition(ClassDeclaration.java:116)
        at sun.tools.javac.SourceClass.basicCheck(SourceClass.java:435)
        at sun.tools.java.ClassDeclaration.getClassDefinition(ClassDeclaration.java:116)
        at sun.tools.javac.SourceClass.basicCheck(SourceClass.java:435)
        at sun.tools.java.ClassDeclaration.getClassDefinition(ClassDeclaration.java:116)
        at sun.tools.javac.SourceClass.basicCheck(SourceClass.java:435)
        at sun.tools.java.ClassDeclaration.getClassDefinition(ClassDeclaration.java:116)
        at sun.tools.javac.SourceClass.basicCheck(SourceClass.java:435)
        at sun.tools.java.ClassDeclaration.getClassDefinition(ClassDeclaration.java:116)
        at sun.tools.javac.SourceClass.basicCheck(SourceClass.java:435)
        at sun.tools.java.ClassDeclaration.getClassDefinition(ClassDeclaration.java:116)
error: An error has occurred in the compiler; please file a bug report (###@###.###).
1 error

using the 1.0betaK compiler (current compiler as of Oct. 11, 1995).

The description field as copied from bug report 1225972 follows:

The JDK prebeta1 compiler generates a StackOverflowError when compiling the
following (incorrect) program

=========================
class Foo extends Foo {
}

=========================
calterra% javac test2.java
java.lang.StackOverflowError
at java.tools.java.ClassDeclaration.getClassDefinition(ClassDeclaration.java:118)
at java.tools.javac.SourceClass.basicCheck(SourceClass.java:439)
at java.tools.java.ClassDeclaration.getClassDefinition(ClassDeclaration.java:118)
at java.tools.javac.SourceClass.basicCheck(SourceClass.java:439)
at java.tools.java.ClassDeclaration.getClassDefinition(ClassDeclaration.java:118)
at java.tools.javac.SourceClass.basicCheck(SourceClass.java:439)
at java.tools.java.ClassDeclaration.getClassDefinition(ClassDeclaration.java:118)
at java.tools.javac.SourceClass.basicCheck(SourceClass.java:439)
at java.tools.java.ClassDeclaration.getClassDefinition(ClassDeclaration.java:118)
at java.tools.javac.SourceClass.basicCheck(SourceClass.java:439)
at java.tools.java.ClassDeclaration.getClassDefinition(ClassDeclaration.java:118)
at java.tools.javac.SourceClass.basicCheck(SourceClass.java:439)
at java.tools.java.ClassDeclaration.getClassDefinition(ClassDeclaration.java:118)
at java.tools.javac.SourceClass.basicCheck(SourceClass.java:439)
at java.tools.java.ClassDeclaration.getClassDefinition(ClassDeclaration.java:118)
at java.tools.javac.SourceClass.basicCheck(SourceClass.java:439)
at java.tools.java.ClassDeclaration.getClassDefinition(ClassDeclaration.java:118)
at java.tools.javac.SourceClass.basicCheck(SourceClass.java:439)
at java.tools.java.ClassDeclaration.getClassDefinition(ClassDeclaration.java:118)
at java.tools.javac.SourceClass.basicCheck(SourceClass.java:439)
error: An error has occurred in the compiler, please file a bug report (###@###.###).
1 error
calterra%

The description field as copied from bug report 1226825 follows:

The following stupid program, typed in error, caused the compiler to crash

class Fifo implementd Fifo { }



gzilla% javac ListFifo.java
java.lang.StackOverflowError
at java.tools.javac.SourceClass.basicCheck(SourceClass.java)
at java.tools.java.ClassDeclaration.getClassDefinition(ClassDeclaration.java)
at java.tools.javac.SourceClass.basicCheck(SourceClass.java)
at java.tools.java.ClassDeclaration.getClassDefinition(ClassDeclaration.java)
at java.tools.javac.SourceClass.basicCheck(SourceClass.java)
at java.tools.java.ClassDeclaration.getClassDefinition(ClassDeclaration.java)
at java.tools.javac.SourceClass.basicCheck(SourceClass.java)
at java.tools.java.ClassDeclaration.getClassDefinition(ClassDeclaration.java)
at java.tools.javac.SourceClass.basicCheck(SourceClass.java)
at java.tools.java.ClassDeclaration.getClassDefinition(ClassDeclaration.java)
at java.tools.javac.SourceClass.basicCheck(SourceClass.java)
at java.tools.java.ClassDeclaration.getClassDefinition(ClassDeclaration.java)
at java.tools.javac.SourceClass.basicCheck(SourceClass.java)
at java.tools.java.ClassDeclaration.getClassDefinition(ClassDeclaration.java)
at java.tools.javac.SourceClass.basicCheck(SourceClass.java)
at java.tools.java.ClassDeclaration.getClassDefinition(ClassDeclaration.java)
at java.tools.javac.SourceClass.basicCheck(SourceClass.java)
at java.tools.java.ClassDeclaration.getClassDefinition(ClassDeclaration.java)
at java.tools.javac.SourceClass.basicCheck(SourceClass.java)
at java.tools.java.ClassDeclaration.getClassDefinition(ClassDeclaration.java)
error: An error has occurred in the compiler, please file a bug report (###@###.###).
1 error
gzilla%