see test/jdk/com/sun/jdi/RedefineTTYLineNumber.java
after class redifinition (redefine <class> <.class file>) jdb reports correct line number, but incorrect source:
==========================================
[jdb] main[1]
> stop in RedefineTTYLineNumberTarg.A
[jdb] Deferring breakpoint RedefineTTYLineNumberTarg.A.
[jdb] It will be set after the class is loaded.
[jdb] main[1]
> run
[jdb] > Set deferred breakpoint RedefineTTYLineNumberTarg.A
[jdb]
[jdb] Breakpoint hit: "thread=main", RedefineTTYLineNumberTarg.A(), line=50 bci=0
[jdb] 50 System.out.println("expected statement printed by jdb");
[jdb]
[jdb] main[1]
> redefine RedefineTTYLineNumberTarg .\\ver1\\RedefineTTYLineNumberTarg.class
[jdb] main[1]
> pop
[jdb] main[1]
> stop in RedefineTTYLineNumberTarg.A
[jdb] Set breakpoint RedefineTTYLineNumberTarg.A
[jdb] main[1]
> cont
[jdb] >
[jdb] Breakpoint hit: "thread=main", RedefineTTYLineNumberTarg.A(), line=49 bci=0
[jdb] 49 public void A() {
[jdb]
[jdb] main[1]
==========================================

2nd breakpoint reported:
[jdb] Breakpoint hit: "thread=main", RedefineTTYLineNumberTarg.A(), line=49 bci=0
[jdb] 49 public void A() {

And it should be
[jdb] Breakpoint hit: "thread=main", RedefineTTYLineNumberTarg.A(), line=49 bci=0
[jdb] 49 System.out.println("expected statement printed by jdb");