jdb [options] [classname] [arguments]
options:    This represents the jdb command-line options (e.g. attach, launch).
classname:  This represents the name of the main class to debug.
arguments:  This represents the arguments that are passed to the main() method of the class.

public class Test
{
    public static void main(String[] args)
    {
        System.out.println("First Line of main function");
        System.out.println("Second Line of main function");
        System.out.println("Third Line of main function");
        int i=0;
        System.out.println("i: " + i);
        i = 2;
        System.out.println("i: " + i);
        while(true)
        {
        }
    }
}

jdb Test

java -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=*:5005 Test

jdb -attach 5005

/jdk/bin/jdb Test
Initializing jdb ...
>

> stop at Test:5
Deferring breakpoint Test:5.
It will be set after the class is loaded.
>

> run
run  Test
Set uncaught java.lang.Throwable
Set deferred uncaught java.lang.Throwable
>
VM Started: Set deferred breakpoint Test:5
Breakpoint hit: "thread=main", Test.main(), line=5 bci=0
5           System.out.println("First Line of main function");

main[1] step
> First Line of main function
Step completed: "thread=main", Test.main(), line=6 bci=8
6            System.out.println("Second Line of main function");

main[1] step
> Second Line of main function
Step completed: "thread=main", Test.main(), line=7 bci=16
7            System.out.println("Third Line of main function");

main[1] print i
i = 0

main[1] locals
Method arguments:
args = instance of java.lang.String[0] (id=841)
Local variables:
i = 0

main[1] where
[1] Test.main (Test.java:10)

main[1] threads
Group system:
(java.lang.ref.Reference$ReferenceHandler)804 Reference Handler running
(java.lang.ref.Finalizer$FinalizerThread)805 Finalizer cond. waiting
(java.lang.Thread)806 Signal Dispatcher running
(java.lang.Thread)803 Notification Thread running
Group main:
(java.lang.Thread)1 main running
Group InnocuousThreadGroup:
(jdk.internal.misc.InnocuousThread)807 Common-Cleaner cond. waiting

main[1] cont
> i: 0
i: 2

connectors -- list available connectors and transports in this VM
run [class [args]] -- start execution of application's main class
threads [threadgroup] -- list threads
thread -- set default thread
suspend [thread id(s)] -- suspend threads (default: all)
resume [thread id(s)] -- resume threads (default: all)
where [ | all] -- dump a thread's stack
wherei [ | all]-- dump a thread's stack, with pc info
up [n frames] -- move up a thread's stack
down [n frames] -- move down a thread's stack
kill -- kill a thread with the given exception object
interrupt -- interrupt a thread
print -- print value of expression
dump -- print all object information
eval -- evaluate expression (same as print)
set = -- assign new value to field/variable/array element
locals -- print all local variables in current stack frame
classes -- list currently known classes
class -- show details of named class
methods -- list a class's methods
fields -- list a class's fields
threadgroups -- list threadgroups
threadgroup -- set current threadgroup
stop [go|thread] []
-- set a breakpoint
-- if no options are given, the current list of breakpoints is printed
-- if "go" is specified, immediately resume after stopping
-- if "thread" is specified, only suspend the thread we stop in
-- if neither "go" nor "thread" are specified, suspend all threads
-- if an integer is specified, only stop in the specified thread
-- "at" and "in" have the same meaning
-- can either be a line number or a method:
-- :
-- .[(argument_type,...)]
clear .[(argument_type,...)]
-- clear a breakpoint in a method
clear : -- clear a breakpoint at a line
clear -- list breakpoints
catch [uncaught|caught|all] |
-- break when specified exception occurs
ignore [uncaught|caught|all] |
-- cancel 'catch' for the specified exception
watch [access|all] .
-- watch access/modifications to a field
unwatch [access|all] .
-- discontinue watching access/modifications to a field
trace [go] methods [thread]
-- trace method entries and exits.
-- All threads are suspended unless 'go' is specified
trace [go] method exit | exits [thread]
-- trace the current method's exit, or all methods' exits
-- All threads are suspended unless 'go' is specified
untrace [methods] -- stop tracing method entrys and/or exits
step -- execute current line
step up -- execute until the current method returns to its caller
stepi -- execute current instruction
next -- step one line (step OVER calls)
cont -- continue execution from breakpoint
list [line number|method] -- print source code
use (or sourcepath) [source file path]
-- display or change the source path
exclude [, ... | "none"]
-- do not report step or method events for specified classes
classpath -- print classpath info from target VM
monitor -- execute command each time the program stops
monitor -- list monitors
unmonitor -- delete a monitor
read -- read and execute a command file
lock -- print lock info for an object
threadlocks [thread id] -- print lock info for a thread
pop -- pop the stack through and including the current frame
reenter -- same as pop, but current frame is reentered
redefine
-- redefine the code for a class
disablegc -- prevent garbage collection of an object
enablegc -- permit garbage collection of an object
!! -- repeat last command
-- repeat command n times
# -- discard (no-op)
help (or ?) -- list commands
dbgtrace [flag] -- same as dbgtrace command line option
version -- print version information
exit (or quit) -- exit debugger
: a full class name with package qualifiers
: a class name with a leading or trailing wildcard ('*')
: thread number as reported in the 'threads' command
: a Java(TM) Programming Language expression.

quit