Week 5

Question 1

What are the two types of exceptions?

Answer 1

Check and unchecked

Question 2

What are checked exceptions?

Answer 2

Exceptions that have to be caught

Question 3

What are unchecked exceptions?

Answer 3

Exceptions that don’t have to be caught e.g. ArrayIndexOutOfBoundsException

Question 4

How do you make your own exception?

Answer 4

You use extend to extend an existing exception, e.g. 
public class MyException extends RuntimeException{ }

Question 5

How do you catch exceptions?

Answer 5

use try catch and finally blocks

Question 6

What’s an example of a try, catch, finally block?

Answer 6

import java.util.Random;
public class PracticeFromLectures {
	public static void main(String[] args) {
		int[] x= new int[10]; //int array with length 10
		Random r = new Random();
		try{
			int pos = r.nextInt(20);
			System.out.println(pos);
			System.out.println(x[pos]);
		} catch(ArrayIndexOutOfBoundsException e){
			System.out.println("Too big!");
		} finally {
			System.out.println("This prints anyway");
		}
	}
}

Question 7

What’s an example of a checked exception?

Answer 7

FileNotFoundException - if the named file doesn’t exist or it’s a directory (or not a file) it’ll throw an exception

Question 8

How do we close FileReader objects?

Answer 8

in the finally block, we can have try and catch. In the try statement, we can close the FileReader.

Question 9

What is the hierarchy of java.io.FileNotFoundException? i.e. where does it inherit from?

Answer 9

java. io.FileNotFoundException inherits from:
java. io.IOException, which inherits from:
java. lang.Exception, which inherits from:
java. lang.Throwable, which inherits from:
java. lang.Object

You can catch a FileNotFoundException as Throwable, Exception and IOException. As you go up, it gets more abstract

Question 10

How do you delegate catches?

Answer 10

You can use the word throws, e.g.
public void myMethod(String a) throws IOException, ArrayIndexOutOfBoundsException { }

If you don’t want to deal with the exception, you can delegate it up to whatever called your method

Question 11

What does the FileReader do?

Answer 11

It allows us to read individual characters

Question 12

How do you use String.split method?

Answer 12

Define a new String:
String line = “Katie Ghaemi, 27”;

Then if we want to split by comma, we will store all of the values in a String array:
String[] tokens = line.split(“,”);