JDBC

import java.sql.*;

public class Sql {

    Connection conn;

    public Sql()    {

    }

    protected void logIn(String a, String b){
        try{
            DriverManager.registerDriver (new oracle.jdbc.driver.OracleDriver());
            conn = DriverManager.getConnection("jdbc:oracle:thin:@//oracle-srv.edvsz.hs-osnabrueck.de:1521/oraclestud", a, b);
            System.out.println("LogIn successful.");
        }catch(SQLException e){
            System.out.println(e.getMessage());
        }
    }

    public void taskOneA()  {
        try{
            Statement stmt = conn.createStatement();
            stmt.executeUpdate("DROP TABLE Kunde");
            System.out.println("Table ''Kunde'' dropped!");
            stmt.executeUpdate("CREATE TABLE Kunde (KNr INT NOT NULL , Name VARCHAR(25))");
            System.out.println("Table ''Kunde'' created!");

            stmt.executeUpdate("INSERT INTO Kunde(KNr, Name) VALUES(1,'Testmeyer')");
            stmt.executeUpdate("INSERT INTO Kunde(KNr, Name) VALUES(2,'Testmoehler')");
            stmt.executeUpdate("INSERT INTO Kunde(KNr, Name) VALUES(3,'Testrichter')");
            stmt.executeUpdate("INSERT INTO Kunde(KNr, Name) VALUES(4,'Testweide')");
            stmt.executeUpdate("INSERT INTO Kunde(KNr, Name) VALUES(5,'Testbaum')");

            System.out.println("Values in ''Kunde'' inserted!");
        }catch(SQLException e){
            System.out.println(e.getMessage());
        }
    }

    public void taskOneB()  {
        String eingabe = "net end", tmp = "";
        boolean repeat = true;
        while(repeat == true)   {
            eingabe = IO.readString("SQL Operation without semicolon and always uppercase. Type 'end' to close the program.\n");
                if(eingabe.contains(" ")){
                    tmp = eingabe.substring(0, eingabe.indexOf(" "));
                }
            switch (eingabe)    {
            case "end":
                repeat = false;
                break;
            default:

                switch(tmp) {
                case "SELECT":
                    try{
                        Statement stmt = conn.createStatement();
                        ResultSet output = stmt.executeQuery(eingabe);
                        ResultSetMetaData outputi = output.getMetaData();
                        for(int i = 1; i < outputi.getColumnCount()+1; i ++)    {
                            System.out.print(outputi.getColumnName(i) + "\t|");
                        }
                        System.out.println();
                        while(output.next())    {
                            for(int i = 1; i < outputi.getColumnCount()+1; i ++)    {
                                System.out.print(output.getString(i)+ "\t|");
                            }
                            System.out.println();
                        }
                        System.out.println("");
                    }catch(SQLException e)  {
                        System.out.println(e.getMessage());
                    }
                    break;
                case "DROP":
                    try{
                        Statement stmt = conn.createStatement();
                        stmt.execute(eingabe);
                        System.out.println("Table deleted!");
                    }catch(SQLException e)  {
                        System.out.println(e.getMessage());
                    }
                    break;
                case "CREATE":
                    try{
                        Statement stmt = conn.createStatement();
                        stmt.execute(eingabe);
                        System.out.println("Table Created!");
                    }catch(SQLException e)  {
                        System.out.println(e.getMessage());
                    }
                    break;
                case "UPDATE":
                    try{
                        Statement stmt = conn.createStatement();
                        stmt.execute(eingabe);
                        System.out.println("Values Updated!");
                    }catch(SQLException e)  {
                        System.out.println(e.getMessage());
                    }
                    break;
                case "INSERT":
                    try{
                        Statement stmt = conn.createStatement();
                        stmt.execute(eingabe);
                        System.out.println("Inserted Values!");
                    }catch(SQLException e)  {
                        System.out.println(e.getMessage());
                    }
                    break;
                case "DELETE":
                    try{
                        Statement stmt = conn.createStatement();
                        stmt.execute(eingabe);
                        System.out.println("Row Deleted!");
                    }catch(SQLException e)  {
                        System.out.println(e.getMessage());
                    }
                    break;
                default:
                    System.out.println("Unknown Command! Only:\nCREATE\nUPDATE\nDROP\nSELECT\nINSERT\nDELETE\n");
                    break;
                }
                break;
            }

        }
        }

    public void taskOneC()  {
        char a = IO.readChar("Interested in using a PreparedStatement to look for the KNr of a Name in Kunde?\nYes[y]\tNo[n]\n");
        if(a == 'y')    {
            try{
                PreparedStatement pstmt = conn.prepareStatement("SELECT KNr, Name FROM Kunde WHERE Name = ?");
                pstmt.setString(1, IO.readString("Type Name: "));
                ResultSet output = pstmt.executeQuery();
                ResultSetMetaData outputi = output.getMetaData();
                for(int i = 1; i < outputi.getColumnCount()+1; i ++)    {
                    System.out.print(outputi.getColumnName(i) + "\t|");
                }
                System.out.println();
                while(output.next())    {
                    for(int i = 1; i < outputi.getColumnCount()+1; i ++)    {
                        System.out.print(output.getString(i)+ "\t|");
                    }
                    System.out.println();
                }
                System.out.println("");
            }catch(SQLException e){
                System.out.println(e.getMessage());
            }
        }
        else    {

        }

    }

    protected void logOut() {
        try{
            conn.close();
            System.out.println("LogOut successful.");
        }catch(SQLException e){
            System.out.println(e.getMessage());
        }
    }
}