add some javadoc

h2/src/main/org/h2/command/dml/SelectGroups.java

@@ -195,7 +195,7 @@ public abstract class SelectGroups {
     }
 
     /**
-     * The session.
+     * The database session.
      */
     final Session session;
 

h2/src/main/org/h2/message/DbException.java

@@ -56,7 +56,7 @@ public class DbException extends RuntimeException {
     private static final Properties MESSAGES = new Properties();
 
     /**
-     * Thrown when OOME exception is happened on handle error
+     * Thrown when OOME exception happens on handle error
      * inside {@link #convert(java.lang.Throwable)}.
      */
     public static final SQLException SQL_OOME =

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

@@ -102,6 +102,7 @@ public class Plan {
      * Calculate the cost of this query plan.
      *
      * @param session the session
+     * @param allColumnsSet calculates all columns on-demand
      * @return the cost
      */
     public double calculateCost(Session session, AllColumnsForPlan allColumnsSet) {

h2/src/main/org/h2/tools/Console.java

@@ -255,6 +255,9 @@ public class Console extends Tool implements ShutdownHandler {
         }
     }
 
+    /**
+     * Overriden by GUIConsole to show a window
+     */
     void show() {
     }
 
@@ -287,6 +290,11 @@ public class Console extends Tool implements ShutdownHandler {
         }
     }
 
+    /**
+     * Open a new browser tab or window with the given URL.
+     *
+     * @param url the URL to open
+     */
     void openBrowser(String url) {
         try {
             Server.openBrowser(url);

h2/src/main/org/h2/value/Value.java

@@ -1496,7 +1496,7 @@ public abstract class Value extends VersionedValue {
     }
 
     /**
-     * Checks value by Integer type numeric range.
+     * Convert to integer, throwing exception if out of range.
      *
      * @param x integer value.
      * @param column Column info.

h2/src/main/org/h2/value/ValueInterval.java

@@ -53,8 +53,8 @@ public class ValueInterval extends Value {
     private final long remaining;
 
     /**
-     * Creates interval value.
-     *
+     * Create a ValueInterval instance.
+     * 
      * @param qualifier
      *            qualifier
      * @param negative