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javafx: How do I call a method in the same class with a button action event? I have an error: "unreported exception Exception must be caught or declared to be thrown".

I am trying to create a save button to save information on a form. I know how to put the button on the GridPane.

I have a method, provided by the professor, to save form information to a file.

I do not know how to fix my code to get the button to call the method.

I've basically tried multiple permutations of moving pieces of code around in any way that might make some sense. I've searched and found what seem to be solutions for this question in other languages, but not in java, let alone using javaFX.

package programmingassignment1;

import javafx.application.Application;

import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.*;
import javafx.stage.Stage;
import java.io.*; //input/output
import javafx.scene.control.Label;
import javafx.scene.control.TextField;

public class Address_ex extends Application {
    String contactLast; 
    @Override
    public void start(Stage primaryStage) {
        TextField tf_contactLast = new TextField();
        contactLast = tf_contactLast.getText();
        Button bt_save = new Button("Save");
        GridPane rootPane = new GridPane(); 
        rootPane.add(new Label("Last Name"), 2, 1);
        rootPane.add(tf_contactLast, 2, 2);    
        rootPane.add(bt_save, 5, 2);


//Setting an action for the Save button        
        File file = new File("AddressBook.txt");
        bt_save.setOnAction(e -> {saveContact(file);});
        //-> unreported exception, fileNotFoundException; must be caught or 
            //declared to be thrown

        Scene scene = new Scene(rootPane, 1000, 500);
        primaryStage.setTitle("Address Book");
        primaryStage.setScene(scene);
        primaryStage.show();
    }
    public void saveContact(File file) throws FileNotFoundException{ 
        //->illegal start of expression
            try{
                PrintWriter output = new PrintWriter (file);
                output.println(contactLast);
                output.close();
            }
            catch(FileNotFoundException e){
                throw new FileNotFoundException(e.getMessage());
            //unreported exception Exception must be caught or declared to be thrown
            }
    }
    public static void main(String[] args) {
        launch(args);
    }
}

Desired: User enters last name & clicks save then a text file is created and the last name is printed in the file.

Mo Hassanpour
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  • Unrelated to your problem: please learn java naming conventions and stick to them. And if you don't know/understand the basics of error handling and compiler error messages, you definitely should read and understand some very basic java tutorial (see the info page of the java tag for options). – kleopatra Oct 06 '19 at 12:30

1 Answers1

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Edit 0: The program works fine when I tried it this way:

    bt_save.setOnAction(e -> {
        try {
            contactLast = tf_contactLast.getText();
            saveContact(file);
        } catch (FileNotFoundException ex) {
            ex.printStackTrace();
        }
    });

Since you are throwing in the method saveContact() a FileNotFoundException you must catch it. Surround the saveContact(file); with a try catch. Also, you were not updating contactLast you can get the text of a TextField in JavaFX with the getText() method. Also, I see you have your class in a package be mindful where you keep the file should be in src.

Edit 1: Also, in the comments they said to use standard Java naming convention seems you are using python naming convention foo_bar in Java it would be like fooBar for methods and variables for classes it would be like FooBar. It is important since for example if you were to use a framework like SpringBoot it relies on the programmer using standard Java naming convention

Dr. Confused
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