java - How to debug a lambda expression using jdb -

i facing problem in clustered production server, manage isolate single instance users, have available debugging, doing using jdb. long intro end. problem need debug code lambda expression

public void method(){     this.privatefield = util.methodcall(); // here breakpoint works     clazz.staticmethod(() -> {        integer x = 1;        long y = 2;         y = x * y; // need break point here        /*           , lot of non related code        */        }); } 

when create breakpoint in jdb in line, ignores break point. pretty sure method called because breakpoint reach first line of method, ignores other, using next , step commands, doesn't work. wrong process ? how debug lambda expressions jdb ?

here answer people landing here , intersted in.

create class

import java.util.concurrent.callable; public class clazz {      public static void main(string[] args) throws exception {         new clazz().method();     }      public void method() throws exception {         clazz.staticmethod(() -> {             integer x = 1;             long y = 2l;             y = x * y; // need break point here             return y;         });     }      private static void staticmethod(callable i) throws exception {         system.out.println("i = " + i.call());     } } 

compile it

javac clazz.java 

start jdb class

jdb clazz initializing jdb ... 

set breakpoint in main method using stop

> stop in clazz.main deferring breakpoint clazz.main. set after class loaded. 

start debugging session run

> run run clazz set uncaught java.lang.throwable set deferred uncaught java.lang.throwable >  vm started: set deferred breakpoint clazz.main  breakpoint hit: "thread=main", clazz.main(), line=6 bci=0 6            new clazz().method(); 

now debugger stopped in main method, before invoking new clazz().method();.

to find line interested in list source

main[1] list 2     3    public class clazz { 4     5        public static void main(string[] args) throws exception { 6 =>         new clazz().method(); 7        } 8         9        public void method() throws exception { 10            clazz.staticmethod(() -> { 11                integer x = 1; main[1] list 12 8         9        public void method() throws exception { 10            clazz.staticmethod(() -> { 11                integer x = 1; 12 =>             long y = 2l; 13                y = x * y; // need break point here 14                return y; 15            }); 16        } 17     

the command list 12 needed list following lines. in output can see want stop @ line 13. let's set new breakpoint there stop command

main[1] stop @ clazz:13 set breakpoint clazz:13 

to continue execution till next breakpoint issue command cont

main[1] cont >  breakpoint hit: "thread=main", clazz.lambda$method$0(), line=13 bci=12 13                y = x * y; // need break point here 

we not on line 13 , example dump values of x , y.

main[1] dump x  x = {     min_value: -2147483648     max_value: 2147483647     type: instance of java.lang.class(reflected class=int, id=568)     digits: instance of char[36] (id=569)     digittens: instance of char[100] (id=570)     digitones: instance of char[100] (id=571)     sizetable: instance of int[10] (id=572)     value: 1     size: 32     bytes: 4     serialversionuid: 1360826667806852920     java.lang.number.serialversionuid: -8742448824652078965 } main[1] dump y  y = {     min_value: -9223372036854775808     max_value: 9223372036854775807     type: instance of java.lang.class(reflected class=long, id=574)     value: 2     size: 64     bytes: 8     serialversionuid: 4290774380558885855     java.lang.number.serialversionuid: -8742448824652078965 } 

going 1 step further

main[1] step >  step completed: "thread=main", clazz.lambda$method$0(), line=14 bci=26 14     

we dump again value of y

main[1] dump y  y = {     min_value: -9223372036854775808     max_value: 9223372036854775807     type: instance of java.lang.class(reflected class=long, id=574)     value: 2     size: 64     bytes: 8     serialversionuid: 4290774380558885855     java.lang.number.serialversionuid: -8742448824652078965 }