diff --git a/app/src/main/java/com/itsaky/androidide/handlers/BaseEventHandler.kt b/app/src/main/java/com/itsaky/androidide/handlers/BaseEventHandler.kt
index 6bc0de1cc..87654d5a8 100644
--- a/app/src/main/java/com/itsaky/androidide/handlers/BaseEventHandler.kt
+++ b/app/src/main/java/com/itsaky/androidide/handlers/BaseEventHandler.kt
@@ -20,34 +20,22 @@ package com.itsaky.androidide.handlers
 import android.content.Context
 import com.itsaky.androidide.EditorActivity
 import com.itsaky.androidide.eventbus.events.Event
+import com.itsaky.androidide.eventbus.events.EventReceiver
 import com.itsaky.androidide.utils.ILogger
-import org.greenrobot.eventbus.EventBus
 
 /**
  * Base class for event handlers.
  *
  * @author Akash Yadav
  */
-abstract class BaseEventHandler {
+abstract class BaseEventHandler : EventReceiver {
 
   protected val log = ILogger.newInstance(javaClass.simpleName)
 
-  /** Registeres this handler with [EventBus]. */
-  fun register() {
-    if (!EventBus.getDefault().isRegistered(this)) {
-      EventBus.getDefault().register(this)
-    }
-  }
-
-  /** Unregisteres this handler from [EventBus]. */
-  fun unregister() {
-    EventBus.getDefault().unregister(this)
-  }
-
   protected open fun checkIsEditorActivity(event: Event): Boolean {
     return event.get(Context::class.java) is EditorActivity
   }
-  
+
   protected open fun logCannotHandle(event: Event) {
     log.warn("Context is not EditorActivity. Cannot handle ${event.javaClass.simpleName} event.")
   }
diff --git a/app/src/main/java/com/itsaky/androidide/handlers/FileTreeActionHandler.kt b/app/src/main/java/com/itsaky/androidide/handlers/FileTreeActionHandler.kt
index fe8c5edca..8bf616f14 100644
--- a/app/src/main/java/com/itsaky/androidide/handlers/FileTreeActionHandler.kt
+++ b/app/src/main/java/com/itsaky/androidide/handlers/FileTreeActionHandler.kt
@@ -48,12 +48,12 @@ import com.itsaky.androidide.utils.ProjectWriter
 import com.itsaky.toaster.Toaster.Type.ERROR
 import com.itsaky.toaster.Toaster.Type.SUCCESS
 import com.unnamed.b.atv.model.TreeNode
-import java.io.File
-import java.util.*
-import java.util.regex.*
 import org.greenrobot.eventbus.EventBus
 import org.greenrobot.eventbus.Subscribe
 import org.greenrobot.eventbus.ThreadMode.MAIN
+import java.io.File
+import java.util.*
+import java.util.regex.*
 
 /**
  * Handles events related to files in filetree.
diff --git a/build-tools/eventbus-events/build.gradle b/build-tools/eventbus-events/build.gradle
index 2432e3fc3..d994e7f10 100644
--- a/build-tools/eventbus-events/build.gradle
+++ b/build-tools/eventbus-events/build.gradle
@@ -26,6 +26,8 @@ java {
 
 dependencies {
     implementation common.jkotlin
+    
+    api project (path: ':build-tools:eventbus')
 }
 
 compileKotlin {
diff --git a/build-tools/projects/src/test/java/com/itsaky/androidide/projects/ExampleUnitTest.kt b/build-tools/eventbus-events/src/main/java/com/itsaky/androidide/eventbus/events/EventReceiver.kt
similarity index 60%
rename from build-tools/projects/src/test/java/com/itsaky/androidide/projects/ExampleUnitTest.kt
rename to build-tools/eventbus-events/src/main/java/com/itsaky/androidide/eventbus/events/EventReceiver.kt
index d208db8d5..87e0911e2 100644
--- a/build-tools/projects/src/test/java/com/itsaky/androidide/projects/ExampleUnitTest.kt
+++ b/build-tools/eventbus-events/src/main/java/com/itsaky/androidide/eventbus/events/EventReceiver.kt
@@ -15,20 +15,26 @@
  *   along with AndroidIDE.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-package com.itsaky.androidide.projects
+package com.itsaky.androidide.eventbus.events
 
-import org.junit.Test
-
-import org.junit.Assert.*
+import org.greenrobot.eventbus.EventBus
 
 /**
- * Example local unit test, which will execute on the development machine (host).
+ * Any class that receives an [Event].
  *
- * See [testing documentation](http://d.android.com/tools/testing).
+ * @author Akash Yadav
  */
-class ExampleUnitTest {
-  @Test
-  fun addition_isCorrect() {
-    assertEquals(4, 2 + 2)
+interface EventReceiver {
+
+  /** Registeres this handler with [EventBus]. */
+  fun register() {
+    if (!EventBus.getDefault().isRegistered(this)) {
+      EventBus.getDefault().register(this)
+    }
   }
-}
\ No newline at end of file
+
+  /** Unregisteres this handler from [EventBus]. */
+  fun unregister() {
+    EventBus.getDefault().unregister(this)
+  }
+}
diff --git a/build-tools/projects/build.gradle b/build-tools/projects/build.gradle
index fd1f63598..59b2e5893 100644
--- a/build-tools/projects/build.gradle
+++ b/build-tools/projects/build.gradle
@@ -29,6 +29,9 @@ android {
 }
 
 dependencies {
+    api project (path: ':build-tools:eventbus')
+    api project (path: ':build-tools:eventbus-events')
+    
     implementation project (path: ':build-tools:tooling-api')
     implementation project (path: ':common')
     
diff --git a/build-tools/projects/src/main/java/com/itsaky/androidide/projects/api/ModuleProject.kt b/build-tools/projects/src/main/java/com/itsaky/androidide/projects/api/ModuleProject.kt
index cc2bd3b5d..a900f3a50 100644
--- a/build-tools/projects/src/main/java/com/itsaky/androidide/projects/api/ModuleProject.kt
+++ b/build-tools/projects/src/main/java/com/itsaky/androidide/projects/api/ModuleProject.kt
@@ -17,6 +17,8 @@
 
 package com.itsaky.androidide.projects.api
 
+import com.itsaky.androidide.eventbus.events.EventReceiver
+import com.itsaky.androidide.projects.util.ClassTrie
 import com.itsaky.androidide.tooling.api.model.GradleTask
 import java.io.File
 
@@ -35,7 +37,10 @@ abstract class ModuleProject(
   tasks: List<GradleTask>
 ) :
   Project(name, description, path, projectDir, buildDir, buildScript, tasks),
-  com.itsaky.androidide.tooling.api.model.ModuleProject {
+  com.itsaky.androidide.tooling.api.model.ModuleProject,
+  EventReceiver {
+
+  private val classes = ClassTrie()
 
   /**
    * Get the source directories of this module (transitive).
@@ -43,4 +48,15 @@ abstract class ModuleProject(
    * @return The source directories.
    */
   abstract fun getSourceDirectories(): Set<File>
+
+  override fun register() {
+    super.register()
+  }
+
+  /** Finds the source files from source directories and indexes them. */
+  fun indexSources() {
+    val sourceDirs = getSourceDirectories()
+  }
+
+  fun findClass(className: String) {}
 }
diff --git a/build-tools/projects/src/main/java/com/itsaky/androidide/projects/util/ClassTrie.kt b/build-tools/projects/src/main/java/com/itsaky/androidide/projects/util/ClassTrie.kt
new file mode 100644
index 000000000..5d4240fce
--- /dev/null
+++ b/build-tools/projects/src/main/java/com/itsaky/androidide/projects/util/ClassTrie.kt
@@ -0,0 +1,167 @@
+/*
+ *  This file is part of AndroidIDE.
+ *
+ *  AndroidIDE is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  AndroidIDE is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *   along with AndroidIDE.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package com.itsaky.androidide.projects.util
+
+import java.util.function.*
+
+/**
+ * Maps classes with their package name segments.
+ *
+ * @author Akash Yadav
+ */
+class ClassTrie {
+
+  val root = Node()
+
+  /**
+   * Appends the class name entry to this trie.
+   *
+   * @param name The fully qualified class name.
+   * @return The added node.
+   */
+  fun append(name: String): Node {
+    val segments = segments(name)
+    var node = root
+    for (segment in segments) {
+      node = node.createChild(segment)
+    }
+    node.isClass = true
+    return node
+  }
+
+  /**
+   * Removes the class name node with the given fully qualified name.
+   *
+   * @param name The fully qualified name of the package segment or class name to remove.
+   */
+  fun remove(name: String) {
+    remove(name, null)
+  }
+
+  /**
+   * Removes the nodes (package segments and class names) with the given fully qualified name. A
+   * [Predicate] can be provided to check which nodes should be deleted.
+   *
+   * @param name The fully qualified name of the package segment or the class.
+   * @param predicate The predicate which can be used to test which entries should be deleted.
+   */
+  fun remove(name: String, predicate: Predicate<Node>?) {
+    val segments = segments(name)
+    val condition = predicate ?: Predicate { it.isClass }
+    var node: Node? = root
+    for (segment in segments) {
+      if (node == null || node.children.isEmpty()) {
+        break
+      }
+
+      val next = node.children[segment]
+      if (next != null && condition.test(next)) {
+        node.children.remove(next.name)
+      }
+      node = next
+    }
+  }
+
+  /**
+   * Finds all class names in the given package.
+   *
+   * @param packageName The package name to list classes from.
+   */
+  fun findClassName(packageName: String): List<String> {
+    val segments = segments(packageName)
+    val classes = mutableListOf<String>()
+    val curr = StringBuilder()
+    var node: Node? = root
+    for (segement in segments) {
+      if (node == null || node.children.isEmpty() || !node.children.containsKey(segement)) {
+        break
+      }
+
+      if (node.isClass) {
+        var name = "$curr.$segement"
+        if (curr.isEmpty()) {
+          name = segement
+        }
+        classes.add(name)
+      } else {
+        if (curr.isNotEmpty()) {
+          curr.append(".")
+        }
+        curr.append(segement)
+      }
+
+      node = node.children[segement]
+    }
+
+    if (node == null || node.children.isEmpty()) {
+      return classes
+    }
+    
+    node.children.values.forEach {
+      addRecursively(it, curr.toString(), classes)
+    }
+    return classes
+  }
+  
+  private fun addRecursively(node: Node, curr: String, classes: MutableList<String>) {
+    val segement = node.name
+    var packageName = curr
+    if (node.isClass) {
+      var name = "$packageName.$segement"
+      if (packageName.isEmpty()) {
+        name = segement
+      }
+      classes.add(name)
+    } else {
+      packageName = if (curr.isEmpty()) {
+        segement
+      } else {
+        "$packageName.$segement"
+      }
+    }
+  
+    if (node.children.isEmpty()) {
+      return
+    }
+    
+    node.children.values.forEach {
+      addRecursively(it, packageName, classes)
+    }
+  }
+  
+  private fun segments(name: String): List<String> {
+    return if (name.contains('.')) {
+      name.split(".")
+    } else {
+      listOf(name)
+    }
+  }
+
+  /** A Node can be a package segment or a class name in the package trie. */
+  class Node(val name: String) {
+
+    internal constructor() : this("")
+
+    val children: MutableMap<String, Node> = mutableMapOf()
+    var isClass = false
+
+    fun createChild(name: String): Node {
+      return children.computeIfAbsent(name) { Node(it) }
+    }
+  }
+}
diff --git a/build-tools/projects/src/test/java/com/itsaky/androidide/projects/util/ClassTrieTest.kt b/build-tools/projects/src/test/java/com/itsaky/androidide/projects/util/ClassTrieTest.kt
new file mode 100644
index 000000000..6432c5138
--- /dev/null
+++ b/build-tools/projects/src/test/java/com/itsaky/androidide/projects/util/ClassTrieTest.kt
@@ -0,0 +1,63 @@
+/*
+ *  This file is part of AndroidIDE.
+ *
+ *  AndroidIDE is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  AndroidIDE is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *   along with AndroidIDE.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package com.itsaky.androidide.projects.util
+
+import com.google.common.truth.Truth.assertThat
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.robolectric.RobolectricTestRunner
+import org.robolectric.annotation.Config
+
+/** @author Akash Yadav */
+@RunWith(RobolectricTestRunner::class)
+@Config(manifest = Config.NONE)
+class ClassTrieTest {
+
+  @Test
+  fun testAppend() {
+    val trie = ClassTrie()
+    trie.append("java.lang.String")
+    trie.append("java.lang.Object")
+    trie.append("java.util.List")
+    trie.append("java.io.File")
+    trie.append("java.nio.file.Path")
+
+    assertThat(trie.findClassName("java.lang"))
+      .containsExactly("java.lang.String", "java.lang.Object")
+    assertThat(trie.findClassName("java.util")).containsExactly("java.util.List")
+    assertThat(trie.findClassName("java.nio")).containsExactly("java.nio.file.Path")
+  }
+  
+  @Test
+  fun testRemoval() {
+    val trie = ClassTrie()
+    trie.append("java.lang.String")
+    trie.append("java.lang.Object")
+    trie.append("java.util.List")
+    trie.append("java.io.File")
+    trie.append("java.nio.file.Path")
+    
+    trie.remove("java.lang.String")
+    trie.remove("java.nio.file.Path")
+    
+    assertThat(trie.findClassName("java.lang"))
+      .containsExactly("java.lang.Object")
+    assertThat(trie.findClassName("java.util")).containsExactly("java.util.List")
+    assertThat(trie.findClassName("java.nio")).isEmpty()
+  }
+}
diff --git a/build-tools/tooling-api-impl/src/test/test-home/.androidide/init/model.jar b/build-tools/tooling-api-impl/src/test/test-home/.androidide/init/model.jar
index 75acf3df5..446ad9acc 100644
Binary files a/build-tools/tooling-api-impl/src/test/test-home/.androidide/init/model.jar and b/build-tools/tooling-api-impl/src/test/test-home/.androidide/init/model.jar differ
diff --git a/build-tools/tooling-api-impl/src/test/test-project/another-java-library/.gitignore b/build-tools/tooling-api-impl/src/test/test-project/another-java-library/.gitignore
new file mode 100644
index 000000000..d16386367
--- /dev/null
+++ b/build-tools/tooling-api-impl/src/test/test-project/another-java-library/.gitignore
@@ -0,0 +1 @@
+build/
\ No newline at end of file
diff --git a/build-tools/tooling-api-impl/src/test/test-project/another-java-library/build.gradle b/build-tools/tooling-api-impl/src/test/test-project/another-java-library/build.gradle
new file mode 100644
index 000000000..78efbac48
--- /dev/null
+++ b/build-tools/tooling-api-impl/src/test/test-project/another-java-library/build.gradle
@@ -0,0 +1,16 @@
+plugins {
+    id 'java-library'
+}
+
+java {
+    sourceCompatibility = JavaVersion.VERSION_11
+    targetCompatibility = JavaVersion.VERSION_11
+}
+
+dependencies {
+    implementation 'io.github.itsaky:nb-javac-android:17.0.0.0'
+}
+
+repositories {
+    mavenCentral ()
+}
\ No newline at end of file
diff --git a/build-tools/tooling-api-impl/src/test/test-project/another-java-library/src/main/java/com/itsaky/androidide/tooling/test/Main.java b/build-tools/tooling-api-impl/src/test/test-project/another-java-library/src/main/java/com/itsaky/androidide/tooling/test/Main.java
new file mode 100644
index 000000000..2a00c845f
--- /dev/null
+++ b/build-tools/tooling-api-impl/src/test/test-project/another-java-library/src/main/java/com/itsaky/androidide/tooling/test/Main.java
@@ -0,0 +1,5 @@
+package com.itsaky.androidide.tooling.test;
+
+public class Main {
+  public static void main(String[] args) {}
+}
diff --git a/build-tools/tooling-api-impl/src/test/test-project/java-library/build.gradle b/build-tools/tooling-api-impl/src/test/test-project/java-library/build.gradle
index 78efbac48..6b600fe3a 100644
--- a/build-tools/tooling-api-impl/src/test/test-project/java-library/build.gradle
+++ b/build-tools/tooling-api-impl/src/test/test-project/java-library/build.gradle
@@ -9,6 +9,7 @@ java {
 
 dependencies {
     implementation 'io.github.itsaky:nb-javac-android:17.0.0.0'
+    implementation project(path: ':another-java-library')
 }
 
 repositories {
diff --git a/build-tools/tooling-api-impl/src/test/test-project/settings.gradle b/build-tools/tooling-api-impl/src/test/test-project/settings.gradle
index 179cc61e1..e45d89cf2 100644
--- a/build-tools/tooling-api-impl/src/test/test-project/settings.gradle
+++ b/build-tools/tooling-api-impl/src/test/test-project/settings.gradle
@@ -1,4 +1,5 @@
 include ':app'
 include ':java-library'
 include ':android-library'
+include ':another-java-library'
 rootProject.name = "TestApp"
\ No newline at end of file