Tell us about debugging applications: how do you debug, do you use a profiler?

For debugging Java applications, I usually use the built-in debugger in the IDE (for example, IntelliJ IDEA or Eclipse). It allows setting breakpoints, stepping through code, inspecting variable values, call stacks, and changing the program's state during execution.

Additionally, for performance analysis and identifying bottlenecks, I use profilers such as VisualVM, YourKit, or the built-in profiler in the IDE. Profilers help understand which methods consume the most CPU or memory, detect memory leaks, frequent garbage collections, etc.

Example of using a debugger:

public class Example {
    public static void main(String[] args) {
        int a = 5;
        int b = 10;
        int c = sum(a, b); // Set breakpoint here
        System.out.println(c);
    }

    public static int sum(int x, int y) {
        return x + y;
    }
}

Run the program in debug mode, stop at the line with the call to sum, check the values of a and b, then step into the sum method to ensure the sum is calculated correctly.

Profilers are helpful when the problem is not obvious, for example, when the application slows down without clear errors. Then, you can see which methods are called most often and optimize them.