Use emptyList() were possible. Also, assign unmodifiableList as soon as possible instead of created in new ArrayLists to return or wrap in unmodifiableCollection in getters.

Author: bytekeeper

src/main/java/bwapi/Game.java

@@ -201,7 +201,7 @@ void init() {
         battleNet = gameData.isBattleNet();
         startLocations = IntStream.range(0, gameData.getStartLocationCount())
                 .mapToObj(i -> new TilePosition(gameData.getStartLocations(i)))
-                .collect(Collectors.toList());
+                .collect(Collectors.collectingAndThen(Collectors.toList(), Collections::unmodifiableList));
         mapWidth = gameData.getMapWidth();
         mapHeight = gameData.getMapHeight();
         mapFileName = gameData.getMapFileName();
@@ -264,9 +264,9 @@ void unitHide(final int id) {
 
     void onFrame(final int frame) {
         if (frame > 0) {
-            allUnits = Collections.unmodifiableList(visibleUnits.stream()
+            allUnits = visibleUnits.stream()
                 .map(i -> units[i])
-                .collect(Collectors.toList()));
+                .collect(Collectors.collectingAndThen(Collectors.toList(), Collections::unmodifiableList));
         }
         getAllUnits().forEach(u -> u.updatePosition(frame));
     }
@@ -1010,7 +1010,7 @@ public boolean canUpgrade(final UpgradeType type, final Unit unit, final boolean
     }
 
     public List<TilePosition> getStartLocations() {
-        return new ArrayList<>(startLocations);
+        return startLocations;
     }
 
     public void printf(final String cstr_format) {

src/main/java/bwapi/Unit.java

@@ -437,7 +437,7 @@ public Unit getTransport() {
 
     public List<Unit> getLoadedUnits() {
         if (getType().spaceProvided() < 1) {
-            return new ArrayList<>();
+            return Collections.emptyList();
         }
         return game.getAllUnits().stream()
                 .filter(u -> equals(u.getTransport()))
@@ -460,7 +460,7 @@ public Unit getCarrier() {
 
     public List<Unit> getInterceptors() {
         if (getType() != Protoss_Carrier && getType() != Hero_Gantrithor) {
-            return new ArrayList<>();
+            return Collections.emptyList();
         }
         return game.getAllUnits().stream()
                 .filter(u -> equals(u.getCarrier()))
@@ -473,7 +473,7 @@ public Unit getHatchery() {
 
     public List<Unit> getLarva() {
         if (!getType().producesLarva()) {
-            return new ArrayList<>();
+            return Collections.emptyList();
         }
         return game.getAllUnits().stream()
                 .filter(u -> equals(u.getHatchery()))
@@ -482,7 +482,7 @@ public List<Unit> getLarva() {
 
     public List<Unit> getUnitsInRadius(final int radius) {
         if (!exists()) {
-            return new ArrayList<>();
+            return Collections.emptyList();
         }
         return game.getUnitsInRectangle(
                 getLeft() - radius,
@@ -495,7 +495,7 @@ public List<Unit> getUnitsInRadius(final int radius) {
     public List<Unit> getUnitsInWeaponRange(final WeaponType weapon) {
         // Return if this unit does not exist
         if (!exists()) {
-            return new ArrayList<>();
+            return Collections.emptyList();
         }
 
         final int max = getPlayer().weaponMaxRange(weapon);

src/main/java/bwta/BWTA.java

@@ -33,31 +33,31 @@ public static void analyze() {
         for (final Area a : bwem.getMap().getAreas()) {
             regionMap.put(a, new Region(a));
         }
-        regions = new ArrayList<>(regionMap.values());
+        regions = Collections.unmodifiableList(new ArrayList<>(regionMap.values()));
 
         chokeMap = new HashMap<>();
         for (final ChokePoint c : bwem.getMap().getChokePoints()) {
             chokeMap.put(c, new Chokepoint(c));
         }
-        chokepoints = new ArrayList<>(chokeMap.values());
+        chokepoints = Collections.unmodifiableList(new ArrayList<>(chokeMap.values()));
 
         baseMap = new HashMap<>();
         for (final Base b : bwem.getMap().getBases()) {
             baseMap.put(b, new BaseLocation(b));
         }
-        baseLocations = new ArrayList<>(baseMap.values());
+        baseLocations = Collections.unmodifiableList(new ArrayList<>(baseMap.values()));
     }
 
     public static List<Region> getRegions() {
-        return new ArrayList<>(regions);
+        return regions;
     }
 
     public static List<Chokepoint> getChokepoints() {
-        return new ArrayList<>(chokepoints);
+        return chokepoints;
     }
 
     public static List<BaseLocation> getBaseLocations() {
-        return new ArrayList<>(baseLocations);
+        return baseLocations;
     }
 
     public static List<BaseLocation> getStartLocations() {

src/main/java/bwta/BaseLocation.java

@@ -1,11 +1,15 @@
 package bwta;
 
+import static java.util.stream.Collectors.collectingAndThen;
+
 import bwapi.Position;
 import bwapi.TilePosition;
 import bwapi.Unit;
 import bwem.Base;
 
+import bwem.unit.NeutralImpl;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 import java.util.stream.Collectors;
 
@@ -28,8 +32,10 @@ public class BaseLocation {
         this.tilePosition = base.getLocation();
         this.minerals = 1;
         this.gas = 1;
-        this.mineralSet = base.getMinerals().stream().map(m -> m.getUnit()).collect(Collectors.toList());
-        this.geyserSet =  base.getGeysers().stream().map(g -> g.getUnit()).collect(Collectors.toList());
+        this.mineralSet = base.getMinerals().stream().map(NeutralImpl::getUnit).collect(
+            collectingAndThen(Collectors.toList(), Collections::unmodifiableList));
+        this.geyserSet =  base.getGeysers().stream().map(NeutralImpl::getUnit).collect(
+            collectingAndThen(Collectors.toList(), Collections::unmodifiableList));
         this.island = base.getArea().getAccessibleNeighbors().isEmpty();
         this.mineralOnly = !mineralSet.isEmpty() && geyserSet.isEmpty();
         this.startLocation = base.isStartingLocation();
@@ -56,11 +62,11 @@ public int gas() {
     }
 
     public List<Unit> getMinerals() {
-        return new ArrayList<>(mineralSet);
+        return mineralSet;
     }
 
     public List<Unit> getGeysers() {
-        return new ArrayList<>(geyserSet);
+        return geyserSet;
     }
 
     public double getGroundDistance(final BaseLocation other) {