Lesson 5: File I/O Exercises

1

Concept

What is the main difference between storing data in RAM vs storing data in a file?

RAM is faster but files are more secure

RAM data is temporary (lost when program ends), file data is permanent

Files can only store text, RAM can store any data type

There is no difference, they are the same

2

File Types

Which of the following is a text-based (human readable) file?

.exe (executable program)

.png (image file)

.java (Java source code)

.mp3 (audio file)

3

File Class

What does this code do?

File myFile = new File(
    "data.txt"
);
                    

Creates a new file called "data.txt" on the disk

Opens and reads the contents of "data.txt"

Creates a File object that represents the path "data.txt" (file may or may not exist)

Deletes the file "data.txt" if it exists

4

Paths

Which is an example of a relative path?

C:/Users/Ahmed/Documents/data.txt

/home/ahmed/projects/data.txt

resources/data.txt

D:/MyProject/src/Main.java

5

File Methods

Which method checks if a file exists on disk?

myFile.isFile()

myFile.exists()

myFile.canRead()

myFile.length()

6

Scanner

What exception must be handled when creating a Scanner with a File?

IOException

FileNotFoundException

NullPointerException

No exception needs to be handled

7

Scanner Methods

What is the difference between next() and nextLine()?

next() reads a word (token), nextLine() reads the entire line

next() reads a line, nextLine() reads a word

They are the same, just different names

next() reads integers, nextLine() reads strings

8

PrintWriter

What happens if you create a PrintWriter for a file that already exists?

An error is thrown

New content is appended to the end of the file

The existing file is overwritten (old content is erased)

A new file with a different name is created

9

Buffers

Why is it important to call close() on a PrintWriter?

To delete the file from memory

To ensure buffered data is written to the file on disk

To encrypt the file for security

It's not important, just a good habit

10

Code Analysis

What will be in output.txt after this code runs?

PrintWriter writer = new PrintWriter(
    "output.txt"
);

writer.print("Hello");
writer.println(" World");
writer.print("Java");

writer.close();
                    

Hello World Java (all on one line)

Hello World (line 1), Java (line 2)

Hello (line 1), World (line 2), Java (line 3)

The file will be empty because print doesn't save