micro optimize map lookups & use a more specialized hashcode for ID-based types

Author: Jasper Geurtz

src/main/java/bwapi/Bullet.java

@@ -197,7 +197,7 @@ public boolean equals(Object o) {
 
     @Override
     public int hashCode() {
-        return Objects.hash(id);
+        return Integer.hashCode(id);
     }
 
     @Override

src/main/java/bwapi/Color.java

@@ -190,7 +190,7 @@ public boolean equals(Object o) {
 
     @Override
     public int hashCode() {
-        return Objects.hash(id);
+        return Integer.hashCode(id);
     }
 
     @Override

src/main/java/bwapi/ConnectedUnitCache.java

@@ -27,18 +27,15 @@ List<Unit> getConnected(final Unit unit) {
             for (final Unit u : game.getAllUnits()) {
                 final Unit owner = condition.apply(u);
                 if (owner != null) {
-                    if (!connectedUnits.containsKey(owner)) {
-                        connectedUnits.put(owner, new ArrayList<>());
-                    }
-                    connectedUnits.get(owner).add(u);
+                    connectedUnits.computeIfAbsent(owner, k -> new ArrayList<>()).add(u);
                 }
             }
             lastUpdate = frame;
         }
-        if (!connectedUnits.containsKey(unit)) {
-            return Collections.emptyList();
-        }
-        return Collections.unmodifiableList(connectedUnits.get(unit));
+        List<Unit> connected = connectedUnits.get(unit);
+        return connected == null ?
+                Collections.emptyList() :
+                Collections.unmodifiableList(connected);
     }
     void reset() {
         lastUpdate = -1;

src/main/java/bwapi/Force.java

@@ -64,7 +64,7 @@ public boolean equals(Object o) {
 
     @Override
     public int hashCode() {
-        return Objects.hash(id);
+        return Integer.hashCode(id);
     }
 
     @Override

src/main/java/bwapi/Player.java

@@ -848,7 +848,7 @@ public boolean equals(Object o) {
 
     @Override
     public int hashCode() {
-        return Objects.hash(id);
+        return Integer.hashCode(id);
     }
 
     @Override

src/main/java/bwapi/Region.java

@@ -250,7 +250,7 @@ public boolean equals(Object o) {
 
     @Override
     public int hashCode() {
-        return Objects.hash(id);
+        return Integer.hashCode(id);
     }
 
     @Override

src/main/java/bwapi/Unit.java

@@ -6345,7 +6345,7 @@ public boolean equals(Object o) {
 
     @Override
     public int hashCode() {
-        return Objects.hash(id);
+        return Integer.hashCode(id);
     }
 
     public int compareTo(final Unit other) {