Use CollectionUtilities and ArrayUtilities for random access.

Use ThreadLocalRandom instead of individual Random objects.

src/de/gurkenlabs/litiengine/abilities/effects/SoundEffect.java

@@ -1,11 +1,10 @@
 package de.gurkenlabs.litiengine.abilities.effects;
 
-import java.util.Random;
-
 import de.gurkenlabs.litiengine.Game;
 import de.gurkenlabs.litiengine.abilities.Ability;
 import de.gurkenlabs.litiengine.entities.ICombatEntity;
 import de.gurkenlabs.litiengine.sound.Sound;
+import de.gurkenlabs.litiengine.util.ArrayUtilities;
 
 public class SoundEffect extends Effect {
   private final Sound[] sounds;
@@ -30,7 +29,6 @@ private Sound getRandomSound() {
       return null;
     }
 
-    final int randomIndex = new Random().nextInt(this.sounds.length);
-    return this.sounds[randomIndex];
+    return ArrayUtilities.getRandom(this.sounds);
   }
 }

src/de/gurkenlabs/litiengine/environment/EntitySpawner.java

@@ -1,14 +1,14 @@
 package de.gurkenlabs.litiengine.environment;
 
 import java.util.List;
-import java.util.Random;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 
 import de.gurkenlabs.litiengine.Game;
 import de.gurkenlabs.litiengine.IGameLoop;
 import de.gurkenlabs.litiengine.entities.IEntity;
 import de.gurkenlabs.litiengine.entities.Spawnpoint;
+import de.gurkenlabs.litiengine.util.CollectionUtilities;
 
 public abstract class EntitySpawner<T extends IEntity> implements IEntitySpawner<T> {
   private static final Logger log = Logger.getLogger(EntitySpawner.class.getName());
@@ -126,13 +126,11 @@ protected void spawnNewEntities() {
       }
       break;
     case ONERANDOMSPAWNPOINT:
-      final int rnd = new Random().nextInt(this.getSpawnPoints().size());
-      this.spawn(this.getSpawnPoints().get(rnd), this.getSpawnAmount());
+      this.spawn(CollectionUtilities.random(this.getSpawnPoints()), this.getSpawnAmount());
       break;
     case RANDOMSPAWNPOINTS:
       for (int i = 0; i < this.getSpawnAmount(); i++) {
-        final int rnd2 = new Random().nextInt(this.getSpawnPoints().size());
-        this.spawn(this.getSpawnPoints().get(rnd2), 1);
+        this.spawn(CollectionUtilities.random(this.getSpawnPoints()), 1);
       }
 
       break;

src/de/gurkenlabs/litiengine/graphics/animation/Animation.java

@@ -2,7 +2,6 @@
 
 import java.util.ArrayList;
 import java.util.List;
-import java.util.Random;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 
@@ -11,6 +10,7 @@
 import de.gurkenlabs.litiengine.IUpdateable;
 import de.gurkenlabs.litiengine.graphics.Spritesheet;
 import de.gurkenlabs.litiengine.resources.Resources;
+import de.gurkenlabs.litiengine.util.CollectionUtilities;
 
 public class Animation implements IUpdateable, ILaunchable {
   public static final int DEFAULT_FRAME_DURATION = 120;
@@ -43,7 +43,7 @@ public Animation(final String name, final Spritesheet spritesheet, final boolean
     this(name, spritesheet, loop, keyFrameDurations);
 
     if (randomizeStart && !this.keyframes.isEmpty()) {
-      this.firstFrame = this.getKeyframes().get(new Random().nextInt(this.getKeyframes().size()));
+      this.firstFrame = CollectionUtilities.random(this.getKeyframes());
     }
   }
 

src/de/gurkenlabs/litiengine/graphics/emitters/Emitter.java

@@ -7,9 +7,9 @@
 import java.util.Arrays;
 import java.util.List;
 import java.util.Map;
-import java.util.Random;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.concurrent.ThreadLocalRandom;
 import java.util.function.Consumer;
 import java.util.stream.Collectors;
 
@@ -38,8 +38,6 @@ public abstract class Emitter extends Entity implements IUpdateable, ITimeToLive
   public static final int DEFAULT_SPAWNAMOUNT = 1;
   public static final int DEFAULT_MAXPARTICLES = 100;
 
-  private static final Random RANDOM = new Random();
-
   private final List<Consumer<Emitter>> finishedConsumer;
   private final CopyOnWriteArrayList<Particle> particles;
   private final List<Color> colors;
@@ -431,7 +429,7 @@ protected Color getRandomParticleColor() {
       return DEFAULT_PARTICLE_COLOR;
     }
 
-    return this.colors.get(RANDOM.nextInt(this.colors.size()));
+    return this.colors.get(ThreadLocalRandom.current().nextInt(this.colors.size()));
   }
 
   protected int getRandomParticleTTL() {
@@ -444,15 +442,15 @@ protected int getRandomParticleTTL() {
       return this.getParticleMaxTTL();
     }
 
-    return RANDOM.nextInt(this.getParticleMaxTTL() - this.getParticleMinTTL()) + this.getParticleMinTTL();
+    return ThreadLocalRandom.current().nextInt(this.getParticleMaxTTL() - this.getParticleMinTTL()) + this.getParticleMinTTL();
   }
 
   protected int getRandomParticleX() {
-    return RANDOM.nextInt((int) this.getWidth());
+    return ThreadLocalRandom.current().nextInt((int) this.getWidth());
   }
 
   protected int getRandomParticleY() {
-    return RANDOM.nextInt((int) this.getHeight());
+    return ThreadLocalRandom.current().nextInt((int) this.getHeight());
   }
 
   /**

src/de/gurkenlabs/litiengine/graphics/emitters/SpritesheetEmitter.java

@@ -2,7 +2,7 @@
 
 import java.awt.Image;
 import java.awt.geom.Point2D;
-import java.util.Random;
+import java.util.concurrent.ThreadLocalRandom;
 
 import de.gurkenlabs.litiengine.graphics.Spritesheet;
 import de.gurkenlabs.litiengine.graphics.emitters.particles.Particle;
@@ -23,9 +23,9 @@ public Spritesheet getSpritesheet() {
   }
 
   protected Image getRandomSprite() {
-    return this.getSpritesheet().getSprite(new Random().nextInt(this.getSpritesheet().getTotalNumberOfSprites()));
+    return this.getSpritesheet().getSprite(ThreadLocalRandom.current().nextInt(this.getSpritesheet().getTotalNumberOfSprites()));
   }
-  
+
   @Override
   protected Particle createNewParticle() {
     return new SpriteParticle(this.getRandomSprite(), this.getRandomParticleTTL());

src/de/gurkenlabs/litiengine/graphics/emitters/SpritesheetEntityEmitter.java

@@ -1,7 +1,7 @@
 package de.gurkenlabs.litiengine.graphics.emitters;
 
 import java.awt.Image;
-import java.util.Random;
+import java.util.concurrent.ThreadLocalRandom;
 
 import de.gurkenlabs.litiengine.entities.IEntity;
 import de.gurkenlabs.litiengine.graphics.Spritesheet;
@@ -23,7 +23,7 @@ public Spritesheet getSpritesheet() {
   }
 
   protected Image getRandomSprite() {
-    return this.getSpritesheet().getSprite(new Random().nextInt(this.getSpritesheet().getTotalNumberOfSprites()));
+    return this.getSpritesheet().getSprite(ThreadLocalRandom.current().nextInt(this.getSpritesheet().getTotalNumberOfSprites()));
   }
 
   @Override

src/de/gurkenlabs/litiengine/util/ArrayUtilities.java

@@ -183,7 +183,7 @@ public static <T> List<T> toList(T[][] arr) {
   public static <T> T getRandom(T[] arr) {
     return getRandom(arr, ThreadLocalRandom.current());
   }
-
+  
   public static <T> T getRandom(T[] arr, Random rand) {
     if (arr.length == 0) {
       return null;

src/de/gurkenlabs/litiengine/util/CollectionUtilities.java

@@ -1,11 +1,11 @@
 package de.gurkenlabs.litiengine.util;
 
 import java.util.Collection;
-import java.util.Random;
+import java.util.concurrent.ThreadLocalRandom;
 
 public final class CollectionUtilities {
   public static <T> T random(Collection<T> coll) {
-    int num = (new Random().nextInt(coll.size()));
+    int num = (ThreadLocalRandom.current().nextInt(coll.size()));
     for (T t : coll) {
       if (--num < 0) {
         return t;

src/de/gurkenlabs/litiengine/util/MathUtilities.java

@@ -30,22 +30,28 @@ public static double round(double value, int places) {
   /**
    * Modifies the value (if necessary) such that it lies within the boundaries of the specified minimum and maximum.
    * 
-   * @param value The value to be clamped.
-   * @param min The minimum value to be accepted.
-   * @param max The maximum value to be accepted.
+   * @param value
+   *          The value to be clamped.
+   * @param min
+   *          The minimum value to be accepted.
+   * @param max
+   *          The maximum value to be accepted.
    * 
    * @return A value clamped to the specified boundaries.
    */
   public static double clamp(final double value, final double min, final double max) {
     return Math.max(min, Math.min(max, value));
   }
-  
+
   /**
    * Modifies the value (if necessary) such that it lies within the boundaries of the specified minimum and maximum.
    * 
-   * @param value The value to be clamped.
-   * @param min The minimum value to be accepted.
-   * @param max The maximum value to be accepted.
+   * @param value
+   *          The value to be clamped.
+   * @param min
+   *          The minimum value to be accepted.
+   * @param max
+   *          The maximum value to be accepted.
    * 
    * @return A value clamped to the specified boundaries.
    */
@@ -56,9 +62,12 @@ public static float clamp(final float value, final float min, final float max) {
   /**
    * Modifies the value (if necessary) such that it lies within the boundaries of the specified minimum and maximum.
    * 
-   * @param value The value to be clamped.
-   * @param min The minimum value to be accepted.
-   * @param max The maximum value to be accepted.
+   * @param value
+   *          The value to be clamped.
+   * @param min
+   *          The minimum value to be accepted.
+   * @param max
+   *          The maximum value to be accepted.
    * 
    * @return A value clamped to the specified boundaries.
    */
@@ -73,13 +82,16 @@ public static byte clamp(final byte value, final byte min, final byte max) {
 
     return value;
   }
-  
+
   /**
    * Modifies the value (if necessary) such that it lies within the boundaries of the specified minimum and maximum.
    * 
-   * @param value The value to be clamped.
-   * @param min The minimum value to be accepted.
-   * @param max The maximum value to be accepted.
+   * @param value
+   *          The value to be clamped.
+   * @param min
+   *          The minimum value to be accepted.
+   * @param max
+   *          The maximum value to be accepted.
    * 
    * @return A value clamped to the specified boundaries.
    */
@@ -95,13 +107,16 @@ public static short clamp(final short value, final short min, final short max) {
 
     return value;
   }
-  
+
   /**
    * Modifies the value (if necessary) such that it lies within the boundaries of the specified minimum and maximum.
    * 
-   * @param value The value to be clamped.
-   * @param min The minimum value to be accepted.
-   * @param max The maximum value to be accepted.
+   * @param value
+   *          The value to be clamped.
+   * @param min
+   *          The minimum value to be accepted.
+   * @param max
+   *          The maximum value to be accepted.
    * 
    * @return A value clamped to the specified boundaries.
    */
@@ -120,9 +135,12 @@ public static int clamp(final int value, final int min, final int max) {
   /**
    * Modifies the value (if necessary) such that it lies within the boundaries of the specified minimum and maximum.
    * 
-   * @param value The value to be clamped.
-   * @param min The minimum value to be accepted.
-   * @param max The maximum value to be accepted.
+   * @param value
+   *          The value to be clamped.
+   * @param min
+   *          The minimum value to be accepted.
+   * @param max
+   *          The maximum value to be accepted.
    * 
    * @return A value clamped to the specified boundaries.
    */

src/de/gurkenlabs/litiengine/util/geom/GeometricUtilities.java

@@ -14,6 +14,7 @@
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
+import java.util.concurrent.ThreadLocalRandom;
 
 public class GeometricUtilities {
   private static final double RAYCAST_EPSILON = 0.01;
@@ -430,8 +431,8 @@ public static List<Point2D> getPointsBetweenPoints(final Point2D point1, final P
   }
 
   public static Point2D getRandomLocation(final double x, final double y, final double width, final double height) {
-    final double xOffset = Math.random() * width;
-    final double yOffset = Math.random() * height;
+    final double xOffset = ThreadLocalRandom.current().nextDouble(width);
+    final double yOffset = ThreadLocalRandom.current().nextDouble(height);
 
     return new Point2D.Double(x + xOffset, y + yOffset);
   }