Added CategorySelect

Data access class that gets all the distinct/unique categories from the database.

helpmehelpapplication/src/main/java/ntnu/systemutvikling/team6/database/Readers/CategorySelect.java

@@ -0,0 +1,53 @@
+package ntnu.systemutvikling.team6.database.Readers;
+
+import java.sql.Connection;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.sql.Statement;
+import java.util.ArrayList;
+import java.util.List;
+import ntnu.systemutvikling.team6.database.DatabaseConnection;
+
+/**
+ * Data access class responsible for getting all the distinct categories from the database.
+ *
+ * <p>All queries are executed against a MySQL database via a {@link DatabaseConnection}.
+ */
+public class CategorySelect {
+  private final DatabaseConnection connection;
+
+    /**
+     *Constructs a new {@code CharitySelect} with the given database connection.
+     *
+     * @param connection the {@link DatabaseConnection} to use for executing queries; must not be
+     *         {@code null}
+     */
+  public CategorySelect(DatabaseConnection connection) {
+    this.connection = connection;
+  }
+
+    /**
+     * Retrieves all the categories listed in the Category table of the database.
+     *
+     * @return a list of strings containing the name of the categories
+     */
+  public List<String> getCategoriesFromDB() {
+    List<String> categories = new ArrayList<>();
+
+    try (Connection conn = connection.getMySqlConnection();
+        Statement stmt = conn.createStatement();
+        ResultSet rs = stmt.executeQuery("SELECT category FROM Categories")) {
+
+      while (rs.next()) {
+        categories.add(rs.getString("category"));
+      }
+
+    } catch (SQLException e) {
+      e.printStackTrace();
+      throw new RuntimeException(
+          "ERROR: Something went wrong during fetching categories from database.");
+    }
+
+    return categories;
+  }
+}