Learn How to Use a Debugger Before Learning a Programming Language

Introduction

In the early stages of programming learning, many educational curricula tend to focus on language syntax and basic structures, but mastering the debugger is extremely important in real-world software development. In fact, proficiently using a debugger can accelerate the development process and dramatically improve your problem-solving capabilities. This article explains in detail the reasons why you should prioritize mastering a debugger over learning the syntax of a programming language, along with the methods to do so.

Basic Functions of a Debugger

A debugger is a tool that allows developers to control code execution in detail and analyze program behavior thoroughly. Key features include setting breakpoints, step execution, and monitoring or changing variable values. By using these features, developers can pause execution at specific lines of code, investigate the internal state of the program in detail, and accurately identify the root causes of bugs.

Frequently Used Functions

Call Stack

The call stack is a feature helpful for tracking the history of functions or methods called during program execution. It is particularly useful in complex projects, as it allows you to visually grasp which methods are being called from where during execution using a debugger. This is highly effective for understanding program flow and helps identify the reasons why specific methods are being invoked unexpectedly.

An example of using the debugger's call stack in a Java program is shown below:

public class CallStackExample {
    public static void main(String[] args) {
        firstMethod();
    }

    public static void firstMethod() {
        secondMethod();
    }

    public static void secondMethod() {
        thirdMethod();
        System.out.println("Second method completed.");
    }

    public static void thirdMethod() {
        System.out.println("Third method reached.");
        // Set a breakpoint here
    }
}

In this example, by setting a breakpoint within thirdMethod, you can use the debugger's call stack feature to clearly see the sequence of method calls starting from main, going through firstMethod and secondMethod, until thirdMethod is called. This information is especially useful when debugging errors to identify which method is causing the issue.

By utilizing the call stack in this way, it becomes easier to track the execution path of a program using a debugger, enabling a deeper understanding of the program's behavior.

Debugging Methods and Sample Code

In particular, a debugging method where you set breakpoints in setter methods and check the call stack to see where an object's field values are being modified is highly effective in transaction script programs where object states are frequently updated. This method is especially helpful for programs with field variables shared across multiple processes.

Below is a Java sample code for setting breakpoints in setter methods and using the call stack to confirm where values are being changed:

public class User {
    private String name;
    private int age;

    // Setter method to set the name
    public void setName(String name) {
        this.name = name; // Set a breakpoint here
    }

    // Setter method to set the age
    public void setAge(int age) {
        this.age = age; // Set a breakpoint here
    }
}

public class Main {
    public static void main(String[] args) {
        User user = new User();
        changeUserInfo(user, "Taro Yamada", 30);
        System.out.println("Updated User Info: Name - " + user.getName() + ", Age - " + user.getAge());
    }

    // Method to change user information
    public static void changeUserInfo(User user, String name, int age) {
        user.setName(name); // Tracked by the debugger
        user.setAge(age);  // Tracked by the debugger
    }
}

How to Use

1. Set breakpoints inside the setName and setAge methods.
2. Run the program using the debugger.
3. When the changeUserInfo method calls setName and setAge, the program will pause at the breakpoints, and the debugger will display the call stack.
4. By checking the call stack, you can track where these setter methods are being called from.

This code is particularly effective when field values might be changed from multiple locations. By using the debugger's call stack feature, you can understand the context (which method called it) in which each setter is executed, thereby improving debugging efficiency.

Why Learn How to Use a Debugger First?

When a new developer joins a project for the first time, it is common to spend more time deciphering existing code than writing new code. Especially when dealing with large-scale projects or legacy code, the codebase is complex, massive, and often poorly documented. By using a debugger, you can directly track the behavior of this complex code and quickly adapt even to unfamiliar languages or frameworks. Visualizing the actual flow of code helps you acquire practical knowledge that is difficult to understand through theory alone.

Reasons Why Code Reading with a Debugger Is Not Actively Taught

The main reason why code reading using a debugger is not widely adopted is that programming education tends to focus on mastering basic syntax and concepts. In many educational programs, exposure to actual debugging processes is limited until beginners have solidified their programming foundations. However, by introducing debuggers early on, beginners can quickly acquire a deep understanding of code and efficient bug-solving techniques, enabling them to gain more practical development skills.

Furthermore, large-scale code or complex and unorganized code (commonly referred to as "dirty code") encountered in practice is rarely experienced at the educational or hobbyist programming level. Coding in such environments provides an excellent opportunity to realize the importance of a debugger and improve actual problem-solving abilities. However, since these experiences are difficult to replicate in educational programs, the use of debuggers is seldom emphasized in educational settings.

If You Can Fix Bugs Using a Debugger, You Can Do the Job

In a professional development environment, fixing bugs is a routine task. The ability to use a debugger effectively is key for a new developer to contribute to a team and become an immediate asset in actual projects. If you can master the debugger, you can approach assigned tasks with confidence and handle more complex and challenging problems.

In Practice, Time Spent Reading Code Is Longer Than Time Spent Writing It

In actual software development work, tasks such as understanding or modifying existing code are often more frequent than new development. In projects, the focus is primarily on tasks related to existing code, such as adding new features or fixing bugs. As a result, it is common to spend more time reading code than writing it. The skill to track code behavior in detail using a debugger is essential for performing these tasks effectively. Therefore, mastering the debugger as a primary problem-solving tool in real-world operations can be considered a mandatory skill for new developers.

The Necessity of Conveying Context to Master Generative AI

Generative AI is extremely convenient and contributes significantly to improving efficiency and productivity in daily tasks. However, to obtain optimal results, it is necessary not just to provide instructions but also to firmly grasp the context of the code being used. Understanding the context—how the code functions, what inputs are expected, and what outputs are required—is the key to having AI perform tasks accurately.

In order to convey this context correctly to AI, developers first need to have a deep understanding of their own code's behavior. By using a debugger, you can observe what is happening at each stage of the code and pinpoint the causes of unexpected behavior or errors. Especially in code involving complex logic or multi-layered processing, grasping the behavior in detail is indispensable.

Furthermore, debuggers provide a means for developers to specifically identify and fix problems in the code, and to confirm in real-time whether those fixes have the intended effect. By accurately understanding and appropriately adjusting the code's context in this way, generative AI can provide more precise and useful outputs. Through this process, developers can maximize the power of generative AI and enhance their ability to rapidly develop higher-quality software products.

The Rise of Generative AI Has Increased the Importance of Debugging

Before the widespread use of generative AI, programmers typically wrote most of their code from scratch. Recently, however, generative AI has taken over the initial creation of code, and the role of the programmer is shifting toward understanding, evolving, or debugging this automatically generated code. This shift has made the debugging process using a debugger even more critical. Generated code often contains subtle bugs or unexpected behaviors, and the ability to effectively identify and fix these is increasingly in demand.

How to Gain Experience in Bug Fixing Using a Debugger

In professional software development, gaining actual work experience is the most effective way to master bug-fixing skills using a debugger. Since the diverse challenges and complex bugs encountered in professional settings are difficult to replicate in classrooms or simulated environments, the experience gained by participating in real projects is extremely valuable.

In the industry, experience in code reading and debugging at a project scale is often more highly valued than proficiency in a specific programming language. This is because problem-solving abilities in actual work environments and insights gained through team collaboration require more than just knowledge of a language. Consequently, there is a tendency to place more importance on the years of specific practical work experience than on the years of experience with a language.

Bug fixing using a debugger provides more than just the technique of correcting code. It is a process of developing the ability to deeply understand and effectively manage program behavior. This experience is essential for growth as a developer and becomes a valuable asset throughout one's career. Therefore, it is recommended that new developers join actual projects as early as possible and directly tackle diverse technical challenges.

Debugging Complex Code: The Trial of a Professional Engineer

For professional software engineers, debugging complex and large-scale codebases is a routine part of the job. In development environments, one often encounters unorganized "spaghetti code"—that is, code that is tightly coupled and difficult to track. Effectively debugging such code and identifying the root cause of issues requires advanced debugging techniques and patience. This patience is precisely what marks the significant difference between hobbyist programming and professional development.

When engineers face debugging, they must not only identify and fix errors but also deepen their understanding of the overall architecture and gain insights to prevent future errors. Through this process, engineers grasp the limitations and possibilities of the system and find more efficient and effective solutions. This is essential not only for solving technical problems but also for better preparing for future engineering challenges.

Summary

Mastering the debugger is an important step when starting to learn programming. By mastering this tool effectively, developers can acquire the ability to solve code problems efficiently and effectively. This significantly improves both the quality and speed of software development. By learning how to use a debugger in parallel with learning a programming language, you can acquire more practical and versatile development skills.

The approach of developing while directly observing code behavior using a debugger provides an excellent opportunity to cultivate actual problem-solving abilities beyond just learning theory. The process of identifying and fixing bugs by executing code line by line brings developers deep insights and practical techniques that cannot be gained from theory alone. This is an essential skill when handling complex systems and is important for dramatically increasing efficiency in actual projects.

Furthermore, the use of a debugger has a wide range of applications, from fixing simple errors to understanding the behavior of complex systems. The experience gained in the process of developers actually getting their hands dirty, facing problems, and solving them provides valuable knowledge and techniques that cannot be learned from textbooks or online tutorials alone. Using a debugger makes it possible to deeply understand how a program is executed and how different components interact, which contributes to the improvement of overall development skills.

In this way, the debugger plays a role beyond being a mere bug-fixing tool and is a powerful means to significantly enhance a developer's technical insights and problem-solving capabilities. In programming education as well, the importance of debuggers should be emphasized more, and their use should be promoted for everyone from beginners to experienced developers.