Use addAll where possible (findbugs).

src/net/sf/freecol/client/control/InGameController.java

@@ -748,10 +748,8 @@ public final class InGameController extends FreeColClientHolder {
             }
         }
         if (!messages.isEmpty()) {
-            for (ModelMessage m : messages) {
-                player.addModelMessage(m);
-                turnReportMessages.add(m);
-            }
+            turnReportMessages.addAll(messages);
+            for (ModelMessage m : messages) player.addModelMessage(m);
             displayModelMessages(false, false);
             fail = true;
         }

src/net/sf/freecol/client/gui/Canvas.java

@@ -781,7 +781,7 @@ public final class Canvas extends JDesktopPane {
         List<Component> allComponents
             = transform(this.getComponents(),
                         c -> !(c instanceof GrayLayer) && c.isValid());
-        for (FreeColDialog<?> fcd : dialogs) allComponents.add(fcd);
+        allComponents.addAll(dialogs);
 
         // Find the position with the least overlap
         int bestScore = Integer.MAX_VALUE;

src/net/sf/freecol/common/model/Map.java

@@ -818,7 +818,21 @@ public class Map extends FreeColGameObject implements Location {
      * @param predicate The <code>Predicate</code> to check.
      * @return A {@code List} of all matching {@code Tile}s.
      */
-    public List<Tile> getTiles(Predicate<Tile> predicate) {
+    public Set<Tile> getTileSet(Predicate<Tile> predicate) {
+        Set<Tile> ret = new HashSet<>();
+        for (Tile t : this.tileList) {
+            if (predicate.test(t)) ret.add(t);
+        }
+        return ret;
+    }
+
+    /**
+     * Get a list of all the tiles that match a predicate.
+     *
+     * @param predicate The <code>Predicate</code> to check.
+     * @return A {@code List} of all matching {@code Tile}s.
+     */
+    public List<Tile> getTileList(Predicate<Tile> predicate) {
         List<Tile> ret = new ArrayList<>();
         for (Tile t : this.tileList) {
             if (predicate.test(t)) ret.add(t);
@@ -915,6 +929,18 @@ public class Map extends FreeColGameObject implements Location {
         return ret;
     }
 
+    /**
+     * Get a shuffled list of all the tiles.
+     *
+     * @param random A pseudo-random number source.
+     * @return A shuffled list of all the {@code Tile}s in this map.
+     */
+    public List<Tile> getShuffledTiles(Random random) {
+        List<Tile> ret = new ArrayList<>(this.tileList);
+        randomShuffle(logger, "All tile shuffle", ret, random);
+        return ret;
+    }
+        
     /**
      * An iterator returning positions in a spiral starting at a given
      * center tile.  The center tile is never included in the returned

src/net/sf/freecol/common/model/Region.java

@@ -438,15 +438,15 @@ public class Region extends FreeColGameObject implements Nameable {
         this.discoveredIn = turn;
         this.discoverable = false;
         List<Region> discov = transform(getChildren(), Region::getDiscoverable);
-        List<Region> result = new ArrayList<>(discov.size()+1);
-        result.add(this);
         for (Region r : discov) {
             r.discoveredBy = player;
             r.discoverer = unit.getId();
             r.discoveredIn = turn;
             r.discoverable = false;
-            result.add(r);
         }
+        List<Region> result = new ArrayList<>(discov.size()+1);
+        result.add(this);
+        result.addAll(discov);
         return result;
     }
 

src/net/sf/freecol/server/generator/SimpleMapGenerator.java

@@ -242,7 +242,7 @@ public class SimpleMapGenerator implements MapGenerator {
         }
 
         // Make new settlements.
-        List<Tile> iTiles = importMap.getTiles(isNotNull(Tile::getIndianSettlement)); 
+        List<Tile> iTiles = importMap.getTileList(isNotNull(Tile::getIndianSettlement)); 
         Set<IndianSettlement> newSettlements = new HashSet<>(iTiles.size());
         for (Tile iTile : iTiles) {
             final IndianSettlement is = iTile.getIndianSettlement();
@@ -391,8 +391,7 @@ public class SimpleMapGenerator implements MapGenerator {
         // order picking out as many as possible suitable tiles for
         // native settlements such that can be guaranteed at least one
         // layer of surrounding tiles to own.
-        List<Tile> allTiles = map.getTiles(alwaysTrue());
-        randomShuffle(logger, "All tile shuffle", allTiles, random);
+        List<Tile> allTiles = map.getShuffledTiles(random);
         final int minDistance = spec.getRange(GameOptions.SETTLEMENT_NUMBER);
         List<Tile> settlementTiles = new ArrayList<>();
         for (Tile tile : allTiles) {

src/net/sf/freecol/server/model/ServerPlayer.java

@@ -667,17 +667,17 @@ public class ServerPlayer extends Player implements TurnTaker {
         cs.add(See.only(this), tiles);
 
         // Remove settlements.  Update formerly owned tiles.
-        tiles.clear();
         List<Settlement> settlements = getSettlementList();
         while (!settlements.isEmpty()) {
             csDisposeSettlement(settlements.remove(0), cs);
         }
 
         // Clean up remaining tile ownerships
-        for (Tile t : game.getMap().getTiles(matchKeyEquals(this, Tile::getOwner))) {
+        tiles.clear();
+        tiles.addAll(game.getMap().getTileList(matchKeyEquals(this, Tile::getOwner)));
+        for (Tile t : tiles) {
             t.cacheUnseen();//+til
             t.changeOwnership(null, null);//-til
-            tiles.add(t);
         }
 
         // Remove units
@@ -973,19 +973,17 @@ public class ServerPlayer extends Player implements TurnTaker {
      * @return A list of tiles whose visibility changed.
      */
     public Set<Tile> exploreMap(final boolean reveal) {
-        List<Tile> tiles = getGame().getMap()
-            .getTiles(t -> this.hasExplored(t) != reveal);
-        Set<Tile> result = new HashSet<>(tiles.size());
+        Set<Tile> tiles = getGame().getMap()
+            .getTileSet(t -> this.hasExplored(t) != reveal);
         for (Tile t : tiles) {
             t.setExplored(this, reveal);//-vis(this)
-            result.add(t);
         }
         invalidateCanSeeTiles();//+vis(this)
         if (!reveal) {
             for (Settlement s : getSettlementList()) exploreForSettlement(s);
             for (Unit u : getUnitSet()) exploreForUnit(u);
         }
-        return result;
+        return tiles;
     }
 
     /**

test/src/net/sf/freecol/common/model/MapTest.java

@@ -186,7 +186,7 @@ public class MapTest extends FreeColTestCase {
             });
         
         int i = 0;
-        for (Tile t : map.getTiles(alwaysTrue())) {
+        for (Tile t : map.getTileList(alwaysTrue())) {
             i++;
             assertTrue(allTiles.remove(t));
         }

test/src/net/sf/freecol/server/generator/MapGeneratorTest.java

@@ -41,7 +41,6 @@ import net.sf.freecol.common.model.Specification;
 import net.sf.freecol.common.model.Tile;
 import net.sf.freecol.common.model.Turn;
 import net.sf.freecol.common.option.MapGeneratorOptions;
-import static net.sf.freecol.common.util.CollectionUtils.*;
 import net.sf.freecol.common.util.LogBuilder;
 import net.sf.freecol.server.FreeColServer;
 import net.sf.freecol.server.model.ServerGame;
@@ -136,7 +135,7 @@ public class MapGeneratorTest extends FreeColTestCase {
 
         // Sufficient land?
         int total = m.getWidth() * m.getHeight();
-        int land = count(m.getTiles(Tile::isLand));
+        int land = m.getTileSet(Tile::isLand).size();
         // Land Mass requirement fulfilled?
         assertTrue(100 * land / total >= g.getMapGeneratorOptions()
                    .getInteger(MapGeneratorOptions.LAND_MASS));