minor updates and javadoc for shared-cache memory connection

Author: Igor Sereda

java/com/almworks/sqlite4java/SQLiteConnection.java

@@ -59,6 +59,11 @@ public final class SQLiteConnection {
    */
   private final File myFile;
 
+  /**
+   * Flag to preserve the cache shared mode when connection was created
+   */
+  private final boolean mySharedCacheMemoryConnection;
+
   /**
    * An incremental number of the instance, used for debugging purposes.
    */
@@ -168,10 +173,12 @@ public final class SQLiteConnection {
    */
   private int myOpenFlags;
 
-  /**
-   * Flag to preserve the cache shared mode when connection was created
-   */
-  private boolean sharedCache;
+  private SQLiteConnection(File dbfile, boolean sharedCacheMemoryConnection) {
+    assert dbfile == null || !sharedCacheMemoryConnection : dbfile + " " + sharedCacheMemoryConnection;
+    myFile = dbfile;
+    mySharedCacheMemoryConnection = sharedCacheMemoryConnection;
+    Internal.logInfo(this, "instantiated [" + myFile + "]");
+  }
 
   /**
    * Creates a connection to the database located in the specified file.
@@ -180,9 +187,7 @@ public final class SQLiteConnection {
    * @param dbfile database file, or null to create an in-memory database
    */
   public SQLiteConnection(File dbfile) {
-    this.sharedCache = false;
-    myFile = dbfile;
-    Internal.logInfo(this, "instantiated [" + myFile + "]");
+    this(dbfile, false);
   }
 
   /**
@@ -192,12 +197,21 @@ public SQLiteConnection(File dbfile) {
    * @see #SQLiteConnection(java.io.File)
    */
   public SQLiteConnection() {
-    this(null);
+    this(null, false);
   }
 
+  /**
+   * <p>Creates a connection to an in-memory temporary database, allowing the user to set the "shared cache" flag.
+   * All in-memory databases opened with {@code sharedCache} equal to {@code true} will share the same data.
+   * </p>
+   *
+   * <p>Database is not opened by the constructor, and the calling thread is insignificant.</p>
+   *
+   * @see #SQLiteConnection()
+   * @see <a href="https://www.sqlite.org/sharedcache.html">Shared Cache in SQLite</a>
+   */
   public SQLiteConnection(boolean sharedCache) {
-    this(null);
-    this.sharedCache = sharedCache;
+    this(null, sharedCache);
   }
 
   /**
@@ -1598,7 +1612,7 @@ private void configureConnection(SWIGTYPE_p_sqlite3 handle) {
 
   private String getSqliteDbName() {
     if (myFile == null) {
-      if (sharedCache) {
+      if (mySharedCacheMemoryConnection) {
         return "file::memory:?cache=shared";
       } else {
         return ":memory:";