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Debugging with Claude Code

Debugging with Claude Code

Debugging is where Claude Code truly shines. It can analyze error messages, trace through code paths, identify root causes, and apply fixes — all through natural language conversation.

Sharing an Error Message

The simplest way to debug is to paste an error directly:

> I'm getting this error when I run my app:
TypeError: Cannot read properties of undefined (reading 'map')
at UserList (src/components/UserList.jsx:15)

Claude Code will:

  1. Read the referenced file (UserList.jsx)
  2. Identify that the data being mapped is undefined
  3. Suggest adding a null check or default value
  4. Offer to apply the fix directly

Debugging a Failing Test

Point Claude Code at a failing test:

> Run pytest tests/test_auth.py and fix any failures

Claude Code will run the test, read the output, analyze the failure, and make corrections.

Debugging with Stack Traces

For complex stack traces, just paste the entire thing:

> Help me understand this Java stack trace and fix the issue:

java.lang.NullPointerException
    at com.app.service.UserService.getUser(UserService.java:42)
    at com.app.controller.UserController.show(UserController.java:28)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

Finding Bugs Without Error Messages

Sometimes you know something is wrong but don’t have an error:

> The login form submits but the user never gets redirected to the dashboard. Can you trace through the login flow and find the issue?

Claude Code will trace the code path from form submission through authentication to redirection, identifying where the flow breaks down.

Performance Debugging

Claude Code can help with performance issues too:

> This API endpoint /api/users is taking 5 seconds to respond. Can you analyze the code and find what's slow?

Common issues Claude Code identifies:

  • N+1 database queries
  • Missing database indexes
  • Inefficient loops or algorithms
  • Unnecessary API calls
  • Large data transfers

Debugging Strategy Tips

  1. Include the full error — Don’t summarize, paste the complete error output
  2. Describe what you expected — “I expected X but got Y” helps narrow down the issue
  3. Mention what you’ve tried — This prevents Claude from suggesting things you’ve already done
  4. Let Claude run commands — Allow it to run tests, check logs, or print debug info

Summary

Claude Code is an excellent debugging partner. It can read errors, trace code paths, run tests, and apply fixes. Next, we’ll explore how Claude Code helps with refactoring.

Previous: Code Generation with Claude Code

Next: Refactoring Code with Claude Code

February 25, 2026

Code Generation with Claude Code

Code Generation with Claude Code

One of Claude Code’s most powerful capabilities is generating code from natural language descriptions. Whether you need a new feature, a utility function, or an entire module, Claude Code can write it for you.

Generating a Simple Function

Let’s say you need a Python function to validate email addresses:

> Create a Python function that validates email addresses using regex

Claude Code will generate something like:

import re

def validate_email(email: str) -> bool:
    """Validate an email address using regex.

    Args:
        email: The email address to validate.

    Returns:
        True if the email is valid, False otherwise.
    """
    pattern = r'^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$'
    return bool(re.match(pattern, email))

Generating a REST API Endpoint

Ask Claude Code to create an entire endpoint:

> Create a FastAPI endpoint for CRUD operations on a "Product" resource with fields: name, price, description, and category

Claude Code will generate the model, routes, and even suggest database integration.

Generating Frontend Components

Claude Code can also write frontend code:

> Create a React component for a search bar with debounced input and autocomplete suggestions

Multi-File Generation

Claude Code can create multiple related files at once:

> Create a Node.js Express middleware for JWT authentication. I need the middleware file, a config file for secrets, and a test file.

Claude Code will create all three files and ensure they work together.

Best Practices for Code Generation

  1. Describe the behavior, not the implementation — Let Claude choose the best approach
  2. Specify your tech stack — “Use Express with TypeScript” gives better results
  3. Mention patterns to follow — “Follow the repository pattern like our other models”
  4. Request tests alongside code — “Also write unit tests for this function”
  5. Review the generated code — Always review before committing

Using Context from Your Codebase

Claude Code automatically reads your project. It will match your existing:

  • Code style and conventions
  • Import patterns
  • Naming conventions
  • Directory structure
  • Error handling patterns

For example, if your project uses camelCase for variables, Claude Code will follow suit.

Generating from Examples

You can point Claude Code to existing code and ask it to generate similar code:

> Look at the UserController in src/controllers/user.py and create a similar ProductController

Summary

Claude Code can generate everything from single functions to multi-file modules. The key is providing clear, specific prompts and reviewing the output. Next, we’ll learn how to use Claude Code for debugging.

Previous: Your First Conversation with Claude Code

Next: Debugging with Claude Code

February 25, 2026

Your First Conversation with Claude Code

Your First Conversation with Claude Code

Now that Claude Code is installed, let’s learn how to interact with it effectively. Claude Code operates as a conversational agent in your terminal — you type natural language prompts and it responds with explanations, code edits, and command executions.

Starting a Session

Navigate to your project and start Claude Code:

cd ~/my-project
claude

You’ll see an interactive prompt where you can type your requests.

Basic Prompting

You can ask Claude Code anything about your codebase. Here are some good starting prompts:

# Understand the project structure
> Give me an overview of this project's architecture

# Ask about specific files
> What does the main function in app.py do?

# Get help with a task
> How would I add a new API endpoint for user profiles?

One-Shot Commands

You can also pass a single prompt directly from the command line without entering interactive mode:

claude "Explain the purpose of this project based on the README"

This is useful for quick questions or scripting.

Multi-Turn Conversations

Claude Code remembers context within a session. You can build on previous messages:

> Show me the User model

# Claude shows the User model code

> Add an email validation method to it

# Claude understands "it" refers to the User model

Slash Commands

Claude Code has built-in slash commands for common actions:

/help          - Show available commands and usage
/clear         - Clear conversation history
/compact       - Summarize and compress the conversation
/cost          - Show token usage and estimated cost
/doctor        - Check Claude Code installation health
/init          - Create a CLAUDE.md file for your project
/review        - Review a pull request
/terminal-setup - Set up terminal integration

Permission System

Claude Code asks for permission before making changes. You’ll see prompts like:

Claude wants to edit file: src/models/user.py
[Allow] [Deny] [Allow All]

You can choose to:

  • Allow – Permit this specific action
  • Deny – Reject this action
  • Allow All – Auto-approve similar actions for this session

Tips for Effective Prompting

  1. Be specific – “Add input validation to the login form” is better than “improve the form”
  2. Give context – “We use Express.js with MongoDB” helps Claude make better decisions
  3. Ask for explanations – “Explain why this approach is better” helps you learn
  4. Iterate – If the first response isn’t perfect, refine your request

Exiting Claude Code

To end your session:

# Type exit, quit, or press Ctrl+C
> /quit

Summary

You now know how to start conversations, use slash commands, and interact effectively with Claude Code. Next, we’ll explore one of its most powerful features: generating code from scratch.

Previous: Introduction to Claude Code – Installation & Setup

Next: Code Generation with Claude Code

February 25, 2026

Introduction to Claude Code – Installation & Setup

Introduction to Claude Code

Claude Code is an agentic coding tool made by Anthropic that lives in your terminal. It can understand your codebase, make edits across multiple files, run commands, and help you work faster as a developer. Think of it as a senior developer pair-programmer that never gets tired.

What Can Claude Code Do?

  • Edit files – Create, modify, and refactor code across your project
  • Run commands – Execute shell commands, run tests, manage git
  • Search codebases – Find files, grep for patterns, understand architecture
  • Debug issues – Analyze errors, trace bugs, suggest fixes
  • Answer questions – Explain code, suggest approaches, teach concepts

Prerequisites

  • Node.js 18 or later
  • An Anthropic API key (or a Claude Pro/Max subscription)
  • A terminal (macOS, Linux, or WSL on Windows)

Installation

Install Claude Code globally using npm:

npm install -g @anthropic-ai/claude-code

Verify the installation:

claude --version

First-Time Setup

Navigate to any project directory and launch Claude Code:

cd my-project
claude

On first launch, Claude Code will:

  1. Ask you to authenticate (either via API key or OAuth with your Anthropic account)
  2. Request permission to access your project directory
  3. Present you with an interactive terminal prompt

Authentication Options

Option 1: Anthropic API Key

Set your API key as an environment variable:

export ANTHROPIC_API_KEY="sk-ant-your-key-here"

Option 2: Claude Pro/Max Subscription

If you have a Claude Pro or Max subscription, Claude Code will open a browser window for OAuth authentication. This is the easiest option if you already have a subscription.

Configuration

Claude Code stores its configuration in ~/.claude/. Key settings can be configured via:

# View current settings
claude config list

# Set a configuration value
claude config set theme dark

Quick Test

Let’s verify everything works. In your project directory, run:

claude "What files are in this directory?"

Claude Code should list the files in your current directory, confirming it can read your filesystem and respond to queries.

Summary

You now have Claude Code installed and configured. In the next tutorial, we’ll learn how to have effective conversations with Claude Code to get the most out of it.

Next: Your First Conversation with Claude Code

February 25, 2026

Spring Boot with Gradle

Gradle is a powerful and flexible build automation system that uses a Groovy-based DSL (Domain Specific Language) or Kotlin-based DSL for defining build tasks. It was designed to overcome the shortcomings of Apache Ant and Apache Maven, and it is widely adopted in the Java community, as well as in Android app development.

Here’s a breakdown of Gradle’s key features and how it works:

  1. Build Scripts: Gradle uses scripts to define and configure builds. These scripts are typically written in Groovy or Kotlin and are interpreted by Gradle. A common name for a build script file is build.gradle.
  2. Project and Task Structure: A Gradle build is made up of one or more projects. Each project can have one or more tasks. For example, a task might compile source files, create a JAR file, or generate Javadoc documentation.
  3. Plugins: Gradle is designed to be extensible, and plugins provide a way to add new functionality. Many plugins are available for Java, Android, and other platforms or tools.
  4. Dependencies: Like Maven, Gradle has robust dependency management capabilities. You can declare dependencies in your build script, and Gradle will download and cache those dependencies for you.
  5. Build Lifecycles: Gradle has a lifecycle for its builds which includes phases like initialization, configuration, and execution. During these phases, different actions are performed, like determining which projects are part of the build, determining dependencies, and executing tasks.
  6. Incremental Builds: Gradle avoids redundant work by only executing tasks that are out-of-date. For instance, if you re-run a build without changing any source files, Gradle recognizes that there’s no need to recompile the source and skips that task.
  7. Customizability: One of Gradle’s strengths is its flexibility. You can create custom tasks, add custom logic, and modify the build process as needed.
  8. Wrapper: Gradle provides a wrapper (typically called gradlew on UNIX-like systems or gradlew.bat on Windows). This is a small script that can download and install the correct version of Gradle for a project, ensuring consistent builds across different environments.

How does it work?

  1. When you run a Gradle command, it starts by evaluating the build script.
  2. It initializes the build, determining which projects will be built.
  3. During the configuration phase, all tasks are configured. At this stage, no task is executed; Gradle just determines the dependencies and order in which tasks will run.
  4. During the execution phase, Gradle runs the necessary tasks in the order determined by their dependencies.
  5. As tasks run, Gradle checks its cache to avoid redoing work (like recompiling unchanged source files).
  6. Once all tasks are executed, the build finishes.

Gradle is a versatile tool that can be used not only for Java projects but also for C++, Python, and more. It has integrations with many IDEs (like IntelliJ IDEA and Android Studio) and CI/CD tools, making it a popular choice for modern development environments.

How to run tests using gradle?

in maven -> mvn test

gradle test

or 

./gradlew test

How to compile java project using gradle?

in maven -> mvn compile

gradle compileJava

or 

./gradlew compileJava

How to package a springboot project using gradle?

in maven -> mvn package

gradle jar

or

./gradlew jar

How to skip tests using gradle?
in maven -> mvn install -DskipTests

gradle assemble -x test

or 

./gradlew assemble -x test

How to list dependencies using gradle?
in maven -> mvn dependency:list

gradle dependencies

or 

./gradlew dependencies

Including a dependency in a Gradle project with Spring Boot typically involves adding the dependency to the build.gradle file. Here’s a step-by-step process:

Ensure You Have the Spring Boot Gradle Plugin:

First, make sure your build.gradle file applies the Spring Boot Gradle plugin and has the Spring Boot dependencies’ BOM (Bill Of Materials):

plugins {
    id 'org.springframework.boot' version '2.5.4' // Use the appropriate version
    id 'io.spring.dependency-management' version '1.0.11.RELEASE' // Again, ensure the version matches your needs
    id 'java'
}

Include the Spring Boot Repositories (if not already added):

Spring Boot dependencies are available in the Maven Central repository, but if you’re using Spring Milestone or Snapshot releases, you might also need the Spring repositories:

repositories {
    mavenCentral()
    // For milestone releases
    maven { url 'https://repo.spring.io/milestone' }
    // For snapshots
    maven { url 'https://repo.spring.io/snapshot' }
}

Add Your Dependency:

Let’s say you want to include Spring Web to create a web application. You would add:

dependencies {
    implementation 'org.springframework.boot:spring-boot-starter-web'
    // ... your other dependencies
}

Note:

  • implementation is a configuration indicating that the dependency is required for compiling the source code of the module and is also required at runtime.
  • The format for the dependency is 'group:artifact:version', but when using the Spring Boot BOM, you often don’t need to specify the version since it’s managed by Spring Boot’s dependency management.

 

Refresh Your Dependencies:

If you’re using an IDE like IntelliJ IDEA or Eclipse, you might need to refresh your project to download the new dependencies. For command-line builds, the next time you run a Gradle task like ./gradlew bootRun, the dependencies will be fetched automatically.

Additional Tip:

To view all the managed versions and dependencies provided by Spring Boot, you can check the spring-boot-dependencies BOM in the Maven Central repository. It’s a useful reference when you want to know the default versions for various libraries that Spring Boot manages.

Remember, the versions and dependencies might vary based on the specific version of Spring Boot you’re using, so always refer to the official Spring Boot documentation or the Spring Initializr website for accurate information.

 

Github Repo Reference

August 10, 2023
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