What are "watches" in IntelliJ and how to use them? -

when debug app, in debug tool window there watches window. have read manual on , over, cannot find practicle usage of watches.

somehow, think cool , useful tool , lack not using it.

can explain when should use , give few samples? ideally, description bound concrete (imaginary) situation better apply in work.

this section allows define expressions you'd see how evolve/change every step of debug process, without manually inspecting available objects , properties. let's take following simple sample intentionally throws npe:

public class watchsample {      static class student {         public static final int credits_required_for_graduation = 10;         private string name;         private integer credits;          public student(string name, integer credits) {             this.name = name;             this.credits = credits;         }          string getname() {             return name;         }          public boolean hasgraduated() {             return credits >= credits_required_for_graduation;         }          public integer getcredits() {             return credits;         }     }      public static void main(string[] args) throws exception {         list<student> students = simulatereadingfromdb();          (student student : students) {             if (student.hasgraduated()) {                 system.out.println("student [" + student.getname() + "] has graduated [" + student.getcredits() + "] credits");             }         }     }      private static list<student> simulatereadingfromdb() {         list<student> students = new arraylist<>(3);         students.add(new student("s1", 15));         students.add(new student("s2", null)); // <- simulate mistake         students.add(new student("s3", 10));         return students;     } } 

at point in time may wonder how come npe , needs fixing. set breakpoint, add few watches , step through lines. you'll end troublemaker in sight:

of course basic example , should taken such. within regular app you'll have more complex scenarios , expressions you'd inspect, , make more sense, example: if (((position > 0 && position < max) || (position < 0 && position > min) && (players(currentplayer).isnotdead() && move.isallowed()) && time.notup())..... in case can evaluate sub-expressions see 1 returns false

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note: make breakpoint conditional program pause when specific event occurs: