IntelliJ IDEA

IntelliJ IDEA is the premier IDE for Java and Kotlin. v2025.1 introduces Java 24 support, K2 Mode (Beta/Stable), and a unified AI Assistant.

When to Use

• Enterprise JVM Development: Building Java, Kotlin, Scala, and Groovy applications with unmatched code intelligence.
• Spring Boot & Microservice Tooling: Visualizing bean dependencies, endpoint mappings, and Spring Data repositories.
• Advanced Automated Refactoring: Safe across-the-board method extraction, interface implementation, and symbol renaming.
• Integrated Profiler & Debugger: Memory snapshots, async stack traces, thread dump analysis, and CPU profiling.

Quick Start

# Run Maven or Gradle build using wrapper
./gradlew bootRun

# Useful keyboard shortcuts:
# Shift+Shift: Search Everywhere
# Ctrl+Alt+L / Cmd+Option+L: Reformat Code
# Shift+F10 / Ctrl+R: Run Application

Core Concepts

Run / Debug Configuration with VM Options

Configuring production-grade local execution:

<!-- .run/ApiApplication.run.xml -->
<component name="ProjectRunConfigurationManager">
  <configuration default="false" name="ApiApplication" type="SpringBootApplicationConfigurationType" factoryName="Spring Boot">
    <module name="api-service.main" />
    <option name="SPRING_BOOT_MAIN_CLASS" value="com.company.api.ApiApplication" />
    <option name="VM_PARAMETERS" value="-Xms512m -Xmx2048m -XX:+UseG1GC -Dspring.profiles.active=local" />
    <extension name="coverage" />
    <method v="2">
      <option name="Make" enabled="true" />
    </method>
  </configuration>
</component>

Inspecting Memory & Thread Dumps with IntelliJ Profiler

Diagnosing memory leaks and deadlocks:

• Click Run with IntelliJ Profiler or attach to running JVM process.
• Open Memory tab to inspect heap allocation by class.
• Click Capture Memory Snapshot (.hprof) to find instances retaining large byte arrays.
• Inspect Threads view to detect thread synchronization bottlenecks.

Structural Search & Replace (SSR)

Finding and modifying patterns across entire codebases:

// Search Template: Catch blocks catching raw generic Exception
catch ($ExceptionType$ $e$) {
    $Statements$;
}
// Constraint: $ExceptionType$ = java.lang.Exception
// Replace Template: Narrow to specific checked domain exceptions

Common Patterns

JVM Memory Profiling and Heap Dump Analysis

Problem: Diagnose memory leaks and high GC overhead in Spring Boot applications.
Solution: Launch app with JVM profiling arguments.

# JVM options for heap profiling
-XX:+HeapDumpOnOutOfMemoryError
-XX:HeapDumpPath=/var/log/heapdump.hprof
-XX:+UseG1GC
-Xms2g -Xmx4g

Best Practices

Do:

• Share standardized team run configurations by checking Store as project file (.run/*.run.xml).
• Use IntelliJ's built-in Git client with visual 3-way merge conflict resolution.
• Allocate sufficient memory to the IDE in Help -> Change Memory Settings (typically 3GB-4GB).
• Use IntelliJ inspections and run Analyze Code -> Inspect Code... before merging PRs.

Don't:

• Commit the entire .idea/ folder; maintain a proper .gitignore excluding workspace.xml and user caches.
• Disable annotation processing when using Lombok or MapStruct; enable in Settings -> Annotation Processors.
• Ignore yellow inspection warnings in Java/Kotlin code; address warnings to keep code maintainable.

Troubleshooting

| Error | Cause | Solution | | :----------------------------------------------- | :------------------------------------------------------------------ | :------------------------------------------------------------------------------------------------------------------ | | Cannot resolve symbol '...' in editor | Project SDK not configured or Maven/Gradle dependencies not loaded. | Open Project Structure > SDKs and ensure JDK is selected, then sync Gradle. | | OutOfMemoryError: Java heap space during build | IntelliJ build process allocated insufficient memory. | Increase memory: Settings > Build, Execution, Deployment > Compiler > Shared build process heap size (2048 MB). | | Red code everywhere after git pull | Indices corrupted. | Click File > Invalidate Caches... > Invalidate and Restart. |

References

• IntelliJ IDEA Documentation