Update Database.java

src/main/java/edu/brown/cs/student/main/Database.java

@@ -21,6 +21,8 @@
 public class Database {
 
 
+//  String urlToDB = "jdbc:sqlite:" + "data/data.sqlite3";
+//  Connection conn=DriverManager.getConnection(urlToDB);
   private static Connection conn = null;
   private static List<String> words = new ArrayList<>();
 
@@ -36,6 +38,27 @@ public class Database {
     * TODO: Initialize the database connection, turn foreign keys on,
     *  and then create the word and corpus tables if they do not exist.
      */
+
+    // this line loads the driver manager class, and must be
+    // present for everything else to work properly
+//    Class.forName("org.sqlite.JDBC");
+    String urlToDB = "jdbc:sqlite:" + filename;
+     conn=DriverManager.getConnection(urlToDB);
+    // these two lines tell the database to enforce foreign keys during operations, and should be present
+    Statement stat = conn.createStatement();
+    stat.executeUpdate("PRAGMA foreign_keys=ON;");
+    stat.close();
+
+    PreparedStatement prep1;
+    prep1 = conn.prepareStatement("CREATE TABLE IF NOT EXISTS corpus (id INTEGER PRIMARY KEY AUTOINCREMENT, filename TEXT);");
+    prep1.executeUpdate();
+    prep1.close();
+
+    PreparedStatement prep2;
+    prep2 = conn.prepareStatement("CREATE TABLE IF NOT EXISTS word "+
+        "(corpus_id INTEGER, word TEXT, FOREIGN KEY (corpus_id) REFERENCES corpus(id) ON DELETE CASCADE);");
+    prep2.executeUpdate();
+    prep2.close();
   }
 
 
@@ -46,9 +69,10 @@ public class Database {
    * @throws SQLException if something goes wrong with a SQL query.
    */
   void readCorpus(String filename) throws SQLException, ClassNotFoundException {
-
-    PreparedStatement prep =
-            conn.prepareStatement("SELECT * from corpus WHERE filename=?");
+    if (conn == null) {
+      System.out.println("suck my gpa");
+    }
+    PreparedStatement prep = conn.prepareStatement("SELECT * from corpus WHERE filename=?");
     prep.setString(1, filename);
     ResultSet rs = prep.executeQuery();
     if (rs.isClosed()) {
@@ -117,7 +141,8 @@ void readAll() throws SQLException {
    Map<String, Integer> getFrequencyMap() throws SQLException {
      Map<String, Integer> freqMap = new HashMap<>();
      //TODO: select all filenames and how many words are associated with those filenames from the database
-    PreparedStatement prep = conn.prepareStatement("");//Your SQL here!
+    PreparedStatement prep = conn.prepareStatement(
+        "SELECT filename, COUNT(*) FROM corpus, word WHERE word.corpus_id = corpus.id GROUP BY filename");//Your SQL here!
     ResultSet rs = prep.executeQuery();
     while (rs.next()) {
         freqMap.put(rs.getString(1), rs.getInt(2));
@@ -138,7 +163,8 @@ Map<String, Integer> getFrequencyMap() throws SQLException {
   Map<String, Integer> getInstanceMap() throws SQLException {
     Map<String, Integer> instMap = new HashMap<>();
     //TODO: select the five most common words from the entire database, and how many times they appear
-    PreparedStatement prep = conn.prepareStatement("");//Your SQL Here!
+    PreparedStatement prep = conn.prepareStatement(
+        "SELECT word, COUNT(*) FROM word GROUP BY word ORDER BY COUNT(*) DESC LIMIT 5;");//Your SQL Here!
     ResultSet rs = prep.executeQuery();
     while (rs.next()) {
       instMap.put(rs.getString(1), rs.getInt(2));
@@ -158,4 +184,3 @@ public List<String> getWords() {
   }
 }
 
-