Oracle Academy Java Programming 3-6: Exceptions and Assertions Lesson PowerPoint

Question

Oracle Academy

Java Programming 3-6: Exceptions and Assertions

Lesson PowerPoint - https://drive.google.com/open?id=0B3GMuhuuq6eANFl4ZEttWFFCM00

1. You would like to write a program that will open a file called “myFile.txt”. Write a try catch statement to open the file and catch the error if the file fails to open.

2. Create an exception called “myException” that prints out an error message when thrown.

3. Create a block of code that utilizes all three types of invariants and asserts their values.

Explanation / Answer

CODE TO QUESTION 1:open a file.

import java.io.File;
import java.io.*;
import java.awt.Desktop;
class papa{
public static void main(String[]args){
if(Desktop.isDesktopSupported())
{
try{
File txt = new File("hello.txt");//place full path of myfile.txt here
Desktop.getDesktop().open(txt);

}
catch(IOException ex)
{
  
}
  
}   
}
}

Code to Question 2:

//creating my own exception

class MyException extends Exception{
MyException(String s){
super(s);
}
}

class ExceptionClass{
  
static void validate(int age)throws MyException{
if(age<18)
throw new MyException("not valid"); //using my Exception
else
System.out.println("welcome to vote");
}

public static void main(String args[]){
try{
validate(13);
}catch(Exception m){System.out.println("Exception occured: "+m);}
  
System.out.println("rest of the code...");
}
}

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