populated "javafx" "piechart" with database value

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package application;

import java.sql.*;
import javafx.application.*;
import javafx.collections.*;
import javafx.scene.Scene;
import javafx.scene.chart.*;
import javafx.scene.chart.PieChart.Data;
import javafx.scene.control.*;
import javafx.scene.layout.*;
import javafx.stage.Stage;

public class PieChat extends Application{
Connection connection;
Statement statement;
TextField t=new TextField("Attendance");
TextField t2=new TextField("CT_Marks");
TextField t3=new TextField("Assignment");
TextField t4=new TextField("Others");
TextField t5=new TextField();
Button b=new Button("Show");
String s,s2,s5,s6;
double i,j,k,l;
ObservableList<Data> answer = FXCollections.observableArrayList();
public void start(Stage stage){

Pane pane=new Pane();
pane.setPrefSize(500,500);
PieChart pchart=new PieChart();
pchart.relocate(0, 70);
pane.getChildren().addAll(t5,b);
t5.relocate(150, 30);
b.relocate(300, 30);
Scene scene=new Scene(pane);
stage.setScene(scene);
stage.show();

b.setOnAction(e ->{
initializeDB();
try{
String sql="select Attendance,CT_Marks,Assignment,Others from performance where Roll='"+t5.getText()+"'";
ResultSet rset=statement.executeQuery(sql);
while(rset.next()){
//t.setText(rset.getString(1));
System.out.print("Searched");
answer.addAll(new PieChart.Data(t.getText(),rset.getDouble(1)),
               new PieChart.Data(t2.getText(),rset.getDouble(2)),new PieChart.Data(t3.getText(),rset.getDouble(3) ),new PieChart.Data(t4.getText(),rset.getDouble(4) ));
pchart.getData().addAll(answer);
pane.getChildren().add(pchart);
}
}catch(Exception ex){
return ;
}
});

}
//database connection//
private void initializeDB() {
try{
Class.forName("com.mysql.jdbc.Driver");
connection=DriverManager.getConnection("jdbc:mysql://localhost/mysql?useUnicode=yes&characterEncoding=UTF-8","root","");
statement=connection.createStatement();
}
catch(Exception ex){
ex.printStackTrace();
}

}
public static void main(String args[]){
launch(args);
}

}