performance - use addAll instead of manually adding each element

h2/src/main/org/h2/command/ddl/AlterTableAddConstraint.java

@@ -6,6 +6,7 @@
 package org.h2.command.ddl;
 
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.HashSet;
 import org.h2.api.ErrorCode;
 import org.h2.command.CommandInterface;
@@ -340,9 +341,7 @@ public class AlterTableAddConstraint extends SchemaCommand {
         }
         Column[] indexCols = idx.getColumns();
         HashSet<Column> indexColsSet = new HashSet<>();
-        for (Column c : indexCols) {
-            indexColsSet.add(c);
-        }
+        Collections.addAll(indexColsSet, indexCols);
         HashSet<Column> colsSet = new HashSet<>();
         for (IndexColumn c : cols) {
             colsSet.add(c.column);

h2/src/main/org/h2/table/MetaTable.java

@@ -1045,9 +1045,7 @@ public class MetaTable extends Table {
             // database settings
             ArrayList<String> settingNames = New.arrayList();
             HashMap<String, String> s = database.getSettings().getSettings();
-            for (String k : s.keySet()) {
-                settingNames.add(k);
-            }
+            settingNames.addAll(s.keySet());
             Collections.sort(settingNames);
             for (String k : settingNames) {
                 add(rows, k, s.get(k));

h2/src/main/org/h2/table/Table.java

@@ -371,9 +371,7 @@ public abstract class Table extends SchemaObjectBase {
             return;
         }
         if (sequences != null) {
-            for (Sequence s : sequences) {
-                dependencies.add(s);
-            }
+            dependencies.addAll(sequences);
         }
         ExpressionVisitor visitor = ExpressionVisitor.getDependenciesVisitor(
                 dependencies);