Use ConcurrentHashMap instead of Collections.synchronizedMap(new HashMap<>())

h2/src/main/org/h2/fulltext/FullTextSettings.java

@@ -10,11 +10,12 @@ import java.sql.PreparedStatement;
 import java.sql.ResultSet;
 import java.sql.SQLException;
 import java.sql.Statement;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.Map;
 import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+
 import org.h2.util.SoftHashMap;
 
 /**
@@ -45,8 +46,7 @@ final class FullTextSettings {
     /**
      * The set of indexes in this database.
      */
-    private final Map<Integer, IndexInfo> indexes = Collections
-            .synchronizedMap(new HashMap<Integer, IndexInfo>());
+    private final ConcurrentHashMap<Integer, IndexInfo> indexes = new ConcurrentHashMap<>();
 
     /**
      * The prepared statement cache.

h2/src/main/org/h2/server/TcpServer.java

@@ -21,6 +21,8 @@ import java.util.HashSet;
 import java.util.Map;
 import java.util.Properties;
 import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+
 import org.h2.Driver;
 import org.h2.api.ErrorCode;
 import org.h2.engine.Constants;
@@ -49,8 +51,7 @@ public class TcpServer implements Service {
      */
     private static final String MANAGEMENT_DB_PREFIX = "management_db_";
 
-    private static final Map<Integer, TcpServer> SERVERS =
-            Collections.synchronizedMap(new HashMap<Integer, TcpServer>());
+    private static final ConcurrentHashMap<Integer, TcpServer> SERVERS = new ConcurrentHashMap<>();
 
     private int port;
     private boolean portIsSet;

h2/src/main/org/h2/store/fs/FilePath.java

@@ -9,10 +9,8 @@ import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
 import java.nio.channels.FileChannel;
-import java.util.Collections;
-import java.util.HashMap;
 import java.util.List;
-import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
 import org.h2.util.MathUtils;
 
 /**
@@ -25,7 +23,7 @@ public abstract class FilePath {
 
     private static FilePath defaultProvider;
 
-    private static Map<String, FilePath> providers;
+    private static ConcurrentHashMap<String, FilePath> providers;
 
     /**
      * The prefix for temporary files.
@@ -66,8 +64,7 @@ public abstract class FilePath {
 
     private static void registerDefaultProviders() {
         if (providers == null || defaultProvider == null) {
-            Map<String, FilePath> map = Collections.synchronizedMap(
-                    new HashMap<String, FilePath>());
+            ConcurrentHashMap<String, FilePath> map = new ConcurrentHashMap<>();
             for (String c : new String[] {
                     "org.h2.store.fs.FilePathDisk",
                     "org.h2.store.fs.FilePathMem",

h2/src/main/org/h2/util/SynchronizedVerifier.java

@@ -5,10 +5,7 @@
  */
 package org.h2.util;
 
-import java.util.Collections;
-import java.util.HashMap;
-import java.util.IdentityHashMap;
-import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.atomic.AtomicBoolean;
 
 /**
@@ -17,10 +14,8 @@ import java.util.concurrent.atomic.AtomicBoolean;
 public class SynchronizedVerifier {
 
     private static volatile boolean enabled;
-    private static final Map<Class<?>, AtomicBoolean> DETECT =
-        Collections.synchronizedMap(new HashMap<Class<?>, AtomicBoolean>());
-    private static final Map<Object, Object> CURRENT =
-        Collections.synchronizedMap(new IdentityHashMap<>());
+    private static final ConcurrentHashMap<Class<?>, AtomicBoolean> DETECT = new ConcurrentHashMap<>();
+    private static final ConcurrentHashMap<Object, Object> CURRENT = new ConcurrentHashMap<>();
 
     /**
      * Enable or disable detection for a given class.

h2/src/test/org/h2/samples/CachedPreparedStatements.java

@@ -10,9 +10,7 @@ import java.sql.DriverManager;
 import java.sql.PreparedStatement;
 import java.sql.SQLException;
 import java.sql.Statement;
-import java.util.Collections;
-import java.util.HashMap;
-import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
 
 /**
  * This sample application shows how to cache prepared statements.
@@ -21,9 +19,7 @@ public class CachedPreparedStatements {
 
     private Connection conn;
     private Statement stat;
-    private final Map<String, PreparedStatement> prepared =
-        Collections.synchronizedMap(
-                new HashMap<String, PreparedStatement>());
+    private final ConcurrentHashMap<String, PreparedStatement> prepared = new ConcurrentHashMap<>();
 
     /**
      * This method is called when executing this sample application from the

h2/src/test/org/h2/samples/TriggerPassData.java

@@ -10,9 +10,8 @@ import java.sql.DriverManager;
 import java.sql.ResultSet;
 import java.sql.SQLException;
 import java.sql.Statement;
-import java.util.Collections;
-import java.util.HashMap;
-import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+
 import org.h2.api.Trigger;
 
 /**
@@ -21,8 +20,7 @@ import org.h2.api.Trigger;
  */
 public class TriggerPassData implements Trigger {
 
-    private static final Map<String, TriggerPassData> TRIGGERS =
-        Collections.synchronizedMap(new HashMap<String, TriggerPassData>());
+    private static final ConcurrentHashMap<String, TriggerPassData> TRIGGERS = new ConcurrentHashMap<>();
     private String triggerData;
 
     /**