jdb is pretty barebones. To make it usable, use 'rlwrap -H ~/.jdbhistory -z pipeto jdb'

basic commands:

jdb> stop in class.method

The following is from:

https://docs.oracle.com/javase/7/docs/technotes/tools/windows/jdb.html

run: After starting jdb, and setting any necessary breakpoints, you can use this command

to start the execution the debugged application. This command is

available only when jdb launches the debugged application (as opposed

to attaching to an existing VM).

cont: Continues execution of the debugged application after a breakpoint, exception, or step. print

Displays Java objects and primitive values. For variables or fields

of primitive types, the actual value is printed. For objects, a

short description is printed. See the dump command below for getting

more information about an object. NOTE: To display local variables,

the containing class must have been compiled with the javac -g

option.

print: supports many simple Java expressions including those with

method invocations, for example:

print MyClass.myStaticField print myObj.myInstanceField print i +

j + k (i, j, k are primities and either fields or local variables)

print myObj.myMethod() (if myMethod returns a non-null) print new

java.lang.String("Hello").length() dump For primitive values, this

command is identical to print. For objects, it prints the current

value of each field defined in the object. Static and instance

fields are included. The dump command supports the same set of

expressions as the print command.

threads: List the threads that are currently running. For each thread,

its name and current status are printed, as well as an index that

can be used for other commands, for example: 4. (java.lang.Thread)0x1

main running In this example, the thread index is 4, the thread

is an instance of java.lang.Thread, the thread name is "main", and

it is currently running, thread Select a thread to be the current

thread. Many jdb commands are based on the setting of the current

thread. The thread is specified with the thread index described in

the threads command above.

where: where with no arguments dumps the

stack of the current thread.

where all: dumps the stack of all threads

in the current thread group. where threadindex dumps the stack of

the specified thread. If the current thread is suspended (either

through an event such as a breakpoint or through the suspend command),

local variables and fields can be displayed with the print and dump

commands. The up and down commands select which stack frame is

current.