Replace Java collection types with Kotlin idiomatic equivalents

Modernize collection usage across the codebase by replacing explicit Java
types with Kotlin stdlib alternatives. This improves type inference,
reduces boilerplate, and aligns with Kotlin best practices.

Changes:
- Replace ArrayList/LinkedHashMap/HashMap constructors with mutableListOf(),
  linkedMapOf(), mutableMapOf()
- Replace Collections.addAll() with collection.addAll(array.asList())
- Replace java.util.Deque with kotlin.collections.ArrayDeque in ArrayPath
- Simplify iterator type declarations (remove explicit java.util.Iterator)
- Remove unnecessary @Suppress annotations for type casts
- Update Path interface to extend MutableCollection instead of java.util.Deque
- Make Cell.getSpatialType() nullable (returns null for TrackBlockPart)
- Remove redundant java.util.* imports throughout

All 662 tests pass. No functional changes to simulation logic.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: bedaHovorka

src/main/kotlin/cz/vutbr/fit/interlockSim/context/AbstractRailwayNetGrid.kt

@@ -12,9 +12,6 @@ package cz.vutbr.fit.interlockSim.context
 import cz.vutbr.fit.interlockSim.objects.cells.Cell
 import cz.vutbr.fit.interlockSim.util.Array2DMap
 import cz.vutbr.fit.interlockSim.util.Point
-import java.util.Iterator
-import java.util.Map.Entry
-import java.util.Set
 import java.util.WeakHashMap
 
 /**
@@ -52,11 +49,9 @@ abstract class AbstractRailwayNetGrid(
 
 	override fun getRows(): Int = _rows
 
-	override fun iterator(): kotlin.collections.Iterator<Entry<Point, Cell>> {
+	override fun iterator(): kotlin.collections.Iterator<Map.Entry<Point, Cell>> {
 		// Build entries from cells and return an immutable iterator
-		@Suppress("UNCHECKED_CAST")
-		val entries = (cells.entries as java.util.Set<Entry<Point, Cell>>).toList()
-		return entries.iterator()
+		return cells.entries.toList().iterator()
 	}
 
 	override fun getLocation(value: Cell): Point? = reverseTable[value]

src/main/kotlin/cz/vutbr/fit/interlockSim/context/DefaultContext.kt

@@ -48,15 +48,8 @@ import jDisco.DiscoException
 import jDisco.Process
 import jDisco.Random
 import java.beans.PropertyChangeSupport
-import java.util.ArrayList
-import java.util.Collection
-import java.util.Collections
 import java.util.EnumSet
 import java.util.IdentityHashMap
-import java.util.LinkedHashMap
-import java.util.List
-import java.util.Map
-import java.util.Set
 import java.util.TreeMap
 
 /**
@@ -90,7 +83,7 @@ abstract class DefaultContext :
 	/**
 	 * List of entry/exit points in the railway network
 	 */
-	private var inouts: ArrayList<InOut> = ArrayList(2)
+	private var inouts: MutableList<InOut> = mutableListOf()
 
 	/**
 	 * Workers for each entry/exit point
@@ -297,7 +290,7 @@ abstract class DefaultContext :
 		val p1 = pi1
 		val p2 = pi2
 
-		val keys: MutableList<Point> = ArrayList()
+		val keys: MutableList<Point> = mutableListOf()
 		val b = bresenham(key1, key2, p1, p2, keys)
 		if (keys.isEmpty()) return null
 
@@ -310,11 +303,9 @@ abstract class DefaultContext :
 
 		if (builtPath != null && builtPath.isNotEmpty()) {
 			@Suppress("UNCHECKED_CAST")
-			val mapToAdd = builtPath as java.util.Map<Point, TrackBlockPart>
+			val mapToAdd = builtPath as MutableMap<Point, TrackBlockPart>
 			getGrid().putMap(mapToAdd)
-			@Suppress("UNCHECKED_CAST")
-			val mapKeys: Set<Point> = mapToAdd.keySet() as Set<Point>
-			linesKeys[trackBlock] = mapKeys
+			linesKeys[trackBlock] = mapToAdd.keys.toSet()
 			requireValidState(!extendedUnorientedGraph.contains(key1, key2)) {
 				"Graph already contains edge between ($key1, $key2)"
 			}
@@ -336,7 +327,7 @@ abstract class DefaultContext :
 		requireValidArgument(bresenham != null && bresenham.isNotEmpty()) {
 			"Bresenham path list cannot be null or empty"
 		}
-		val map: MutableMap<Point, TrackBlockPart> = LinkedHashMap()
+		val map: MutableMap<Point, TrackBlockPart> = linkedMapOf()
 		var from = key1
 		var middle = bresenham[0]
 		var part: TrackBlockPart?
@@ -559,7 +550,7 @@ abstract class DefaultContext :
 				)
 			}
 		}
-		if (nodeCell is InOut) getInOuts().add(nodeCell as InOut)
+		if (nodeCell is InOut) inouts.add(nodeCell as InOut)
 		changeSupport.firePropertyChange(ContextChangeListener.CELL_ADDED, null, key)
 		logger.trace { "Added ${nodeCell.javaClass.simpleName} at (${key.x},${key.y})" }
 	}
@@ -926,7 +917,7 @@ abstract class DefaultContext :
 		if (types == null || types.isEmpty()) {
 			allowedReportTypes.clear()
 		} else {
-			Collections.addAll(allowedReportTypes, *types)
+			allowedReportTypes.addAll(types.asList())
 		}
 	}
 

src/main/kotlin/cz/vutbr/fit/interlockSim/context/DefaultRailWayNetGrid.kt

@@ -14,10 +14,6 @@ import cz.vutbr.fit.interlockSim.objects.cells.Cell
 import cz.vutbr.fit.interlockSim.objects.cells.TrackBlockPart
 import cz.vutbr.fit.interlockSim.util.Point
 import java.util.AbstractSet
-import java.util.Iterator
-import java.util.Map
-import java.util.Map.Entry
-import java.util.Set
 
 /**
  * Grid represantation
@@ -27,18 +23,17 @@ class DefaultRailWayNetGrid(
 	rows: Int
 ) : AbstractRailwayNetGrid(cols, rows) {
 	private inner class KeySet(
-		private val set: Set<Entry<Point, Cell>>
+		private val set: Set<Map.Entry<Point, Cell>>
 	) : AbstractSet<Point>() {
 		override fun iterator(): MutableIterator<Point> {
-			@Suppress("UNCHECKED_CAST")
-			val delegate: Iterator<Entry<Point, Cell>> = (set.iterator() as Iterator<Entry<Point, Cell>>)
+			val delegate: Iterator<Map.Entry<Point, Cell>> = set.iterator()
 			return PointIterator(delegate)
 		}
 
 		private inner class PointIterator(
-			private val delegate: Iterator<Entry<Point, Cell>>
+			private val delegate: Iterator<Map.Entry<Point, Cell>>
 		) : MutableIterator<Point> {
-			private var next: Entry<Point, Cell>? = null
+			private var next: Map.Entry<Point, Cell>? = null
 
 			override fun next(): Point {
 				next = delegate.next()
@@ -50,10 +45,10 @@ class DefaultRailWayNetGrid(
 			override fun remove() {
 				if (delegate is MutableIterator<*>) {
 					// Save the cell BEFORE removing from cells map
-					// (Entry.getValue() will fail after removal since it looks up the key)
+					// (Map.Entry.getValue() will fail after removal since it looks up the key)
 					val cell = next?.value
 					// Remove from cells map via delegate
-					(delegate as MutableIterator<Entry<Point, Cell>>).remove()
+					(delegate as MutableIterator<Map.Entry<Point, Cell>>).remove()
 					// Also remove from reverse table to maintain invariant
 					if (cell != null) {
 						getReverseTable().remove(cell)
@@ -117,11 +112,9 @@ class DefaultRailWayNetGrid(
 	 * @param map of point to trackblock part
 	 */
 	@Synchronized
-	fun putMap(map: java.util.Map<Point, TrackBlockPart>) {
-		val iter = map.entrySet().iterator()
-		while (iter.hasNext()) {
-			val entry = iter.next()
-			put(entry.key, entry.value)
+	fun putMap(map: Map<Point, TrackBlockPart>) {
+		for ((key, value) in map) {
+			put(key, value)
 		}
 	}
 
@@ -171,9 +164,9 @@ class DefaultRailWayNetGrid(
 	 * All cell in grid
 	 * @return set of cells
 	 */
-	fun keySet(): Set<Point> {
+	fun keySet(): MutableSet<Point> {
 		@Suppress("UNCHECKED_CAST")
-		val entries = getCells().entries as java.util.Set<Entry<Point, Cell>>
-		return KeySet(entries) as Set<Point>
+		val entries = getCells().entries as Set<Map.Entry<Point, Cell>>
+		return KeySet(entries) as MutableSet<Point>
 	}
 }

src/main/kotlin/cz/vutbr/fit/interlockSim/context/RailwayNetGrid.kt

@@ -11,16 +11,14 @@ package cz.vutbr.fit.interlockSim.context
 
 import cz.vutbr.fit.interlockSim.objects.cells.Cell
 import cz.vutbr.fit.interlockSim.util.Point
-import java.util.Iterator
-import java.util.Map.Entry
 
 /**
  * Read-only access interface to Grid...
  *
  * aby bylo rozhrani dokonale tak iterator vraceny implementaci tohoto rozhrani
  * musi u [Iterator.remove] hazet [UnsupportedOperationException]
  */
-interface RailwayNetGrid : Iterable<Entry<Point, Cell>> {
+interface RailwayNetGrid : Iterable<Map.Entry<Point, Cell>> {
 	/**
 	 * @param x
 	 * @param y

src/main/kotlin/cz/vutbr/fit/interlockSim/context/SimulationContext.kt

@@ -20,7 +20,6 @@ import cz.vutbr.fit.interlockSim.objects.tracks.TrackBlock
 import cz.vutbr.fit.interlockSim.objects.tracks.TrackSection
 import cz.vutbr.fit.interlockSim.sim.InOutWorker
 import cz.vutbr.fit.interlockSim.exceptions.SimulationException
-import java.util.Collection
 import java.util.EnumSet
 
 /**

src/main/kotlin/cz/vutbr/fit/interlockSim/gui/action/NodeCellAction.kt

@@ -20,7 +20,6 @@ import java.awt.Color
 import java.awt.RenderingHints
 import java.awt.event.ActionEvent
 import java.awt.image.BufferedImage
-import java.util.HashMap
 import javax.swing.AbstractAction
 import javax.swing.Icon
 import javax.swing.ImageIcon
@@ -43,8 +42,8 @@ class NodeCellAction(
 	companion object {
 		private const val iconSize: Int = 20
 		private val editorCellRenderer = EditorCellRenderer(iconSize, iconSize)
-		private val renderingHints: HashMap<RenderingHints.Key, Any> =
-			HashMap<RenderingHints.Key, Any>().apply {
+		private val renderingHints: MutableMap<RenderingHints.Key, Any> =
+			mutableMapOf<RenderingHints.Key, Any>().apply {
 				put(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON)
 				put(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_SPEED)
 			}

src/main/kotlin/cz/vutbr/fit/interlockSim/objects/cells/AbstractCell.kt

@@ -11,19 +11,18 @@ package cz.vutbr.fit.interlockSim.objects.cells
 
 import cz.vutbr.fit.interlockSim.exceptions.requireValidState
 import java.util.EnumSet
-import java.util.Set
 
 /**
  * Base implementation of {@link Cell}
  *
  */
 abstract class AbstractCell : Cell {
-	protected fun joinsOnLine(): Set<Cell.Segment> {
+	protected fun joinsOnLine(): MutableSet<Cell.Segment> {
 		val st = getSpatialType()
 		requireValidState(st != null) { "Spatial type is null for cell: $this" }
 		val arr2set = arr2set(st!!.segments)
 		requireValidState(arr2set.size == 2) { "Expected 2 segments but got ${arr2set.size}" }
-		return arr2set
+		return arr2set.toMutableSet()
 	}
 
 	protected fun secondOnLine(from: Cell.Segment?): Cell.Segment? {

src/main/kotlin/cz/vutbr/fit/interlockSim/objects/cells/Cell.kt

@@ -11,7 +11,6 @@ package cz.vutbr.fit.interlockSim.objects.cells
 
 import cz.vutbr.fit.interlockSim.exceptions.requireValidState
 import cz.vutbr.fit.interlockSim.util.Point
-import java.util.Set
 
 /**
  * Cell in Grid
@@ -122,7 +121,7 @@ interface Cell {
 	 *
 	 * @return {@link SpatialType}
 	 */
-	fun getSpatialType(): SpatialType
+	fun getSpatialType(): SpatialType?
 
 	/**
 	 * @return Possible joins

src/main/kotlin/cz/vutbr/fit/interlockSim/objects/cells/InOut.kt

@@ -14,7 +14,6 @@ import cz.vutbr.fit.interlockSim.objects.cells.RailSemaphore.Signal
 import cz.vutbr.fit.interlockSim.objects.paths.PathElement
 import cz.vutbr.fit.interlockSim.exceptions.PathSeparatorChangeException
 import java.util.EnumSet
-import java.util.Set
 
 /**
  * predstavuje spojeni s externi zeleznicni siti

src/main/kotlin/cz/vutbr/fit/interlockSim/objects/cells/OrientedNodeCell.kt

@@ -12,7 +12,6 @@ package cz.vutbr.fit.interlockSim.objects.cells
 import cz.vutbr.fit.interlockSim.exceptions.requireSimulationNotNull
 import cz.vutbr.fit.interlockSim.objects.paths.OrientedPathSeparator
 import java.util.EnumSet
-import java.util.Set
 
 /**
  * Base implementation of {@link OrientedPathSeparator}