Tutorial 34 (Handling Exceptions)

//Tutorial 34 (Handling Exceptions)
//Exception is part of an error handling mechanism



//---------------------------------------------------------------------------------------------------------------------------------------
//demo1/App.java:

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;



public class App {

    public static void main(String[] args) throws FileNotFoundException {

        File file = new File("test.txt");

        FileReader fr = new FileReader(file);
    }

}


/*when you run it you should get an error in red:

Exception in thread "main" java.io.FileNotFoundException: test.txt (The system cannot find the file specified)
    at java.io.FileInputStream.open(Native Method)
    at java.io.FileInputStream.<init>(Unknown Source)
    at java.io.FileReader.<init>(Unknown Source)
    at App.main(App.java:16)
*/




//---------------------------------------------------------------------------------------------------------------------------------------
//demo2/App.java:

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;

public class App {

    public static void main(String[] args) {
        File file = new File("test.txt");

        try {
            FileReader fr = new FileReader(file);

            // This will not be executed if an exception is thrown.
            System.out.println("Continuing ....");
        } catch (FileNotFoundException e) {
            System.out.println("File not found: " + file.toString());  //Remember to Right click>new>file>text.txt or else you will get an error: File Not Found test.txt
        }

        System.out.println("Finished.");
    }

}



/*run results:
Continuing ....
Finished.
*/





//---------------------------------------------------------------------------------------------------------------------------------------
//demo3/App.java:
package demo3;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;

public class App {

    public static void main(String[] args) {
        try {
            openFile();
        } catch (FileNotFoundException e) {
            System.out.println("Could not open file"); //if error, user will see "Could not open file"
        }
    }

    public static void openFile() throws FileNotFoundException {
        File file = new File("test.txt");

        FileReader fr = new FileReader(file);

    }

}


/*
run results should be blank if successful
*/