Help needed: Code writing to a database freezes

Question

Dear Java forum
I have the following problem. I had written the attached piece of code to write into a database I had previously created. The connection to the database is made: however my machine freezes at the write statement (no exception is thrown and no error or warning is given). Is there a way through?
Connection con = null;
          try
               String url = "jdbc:mysql://xxxxx";
          Class.forName ("com.mysql.jdbc.Driver").newInstance ();
          con = DriverManager.getConnection (url, "xxxxxx", pass);
          System.out.println("Database link performed &&&&&");
          catch (Exception e2) {
          System.out.println("Couldn't connect to database");
          System.out.println(e2.toString());
          System.exit(-1);
          PreparedStatement dataInsertStmt = con.prepareStatement("INSERT INTO reaction_table_1" + "first_reactant" + ", " + "second_reactant" + ", " + "first_product" + ", " + "second_product" + "VALUES (?, ?, ?, ?)");
          for(int rowctr=0; rowctr<5 ; rowctr++)
               for (int rcolctr=1; rcolctr<5; rcolctr++)
                    dataInsertStmt.setString(rcolctr, Reaction_Table[rowctr][rcolctr]);                // assignment of first reactant, second reactant etc
Problem statement >>>>>>>>>     dataInsertStmt.executeQuery();               }
               System.out.println("-->> Row update "+rowctr);
          };

Answer 1

There are several problems here. The first is your use of multiple concatenated strings; that is making it difficult to see the problem. This line
PreparedStatement dataInsertStmt = con.prepareStatement("INSERT INTO reaction_table_1" + "first_reactant" + ", " + "second_reactant" + ", " + "first_product" + ", " + "second_product" + "VALUES (?, ?, ?, ?)");is equivalent to this:
PreparedStatement dataInsertStmt = con.prepareStatement("INSERT INTO reaction_table_1first_reactant, second_reactant, first_product, second_productVALUES (?, ?, ?, ?)");Note the lack of spaces and correct parentheses. Try this instead:
PreparedStatement dataInsertStmt = con.prepareStatement("INSERT INTO reaction_table_1 (first_reactant, second_reactant, first_product, second_product) VALUES (?, ?, ?, ?)");Another problem is your array indeces. On this line,
dataInsertStmt.setString(rcolctr, Reaction_Table[rowctr][rcolctr])it looks like [rowctr][rcolctr] should be [rowctr][rcolctr-1]. JDBC may be 1-indexed, but your arrays are zero-indexed (at least they should be).
Another problem item is the use of executeQuery() - use executeUpdate() instead.
Another problem is the placement of the executeQuery / executeUpdate - it should go after the for loop where you currently have it, the way it's written now it will be executed each time you set a parameter; what you really want is for it to be executed after setting all the parameters.
Despite these problems, I am very surprised that the machine freezes - I would expect an SQL exception to be thrown. Not sure what's up with that.