Text I/O

Question 1

What classes are commonly used in Java for text file I/O?

Answer 1

Scanner for reading, PrintWriter for writing .
they allow reading/writing and numeric values

Question 2

what are the main topics covered in Java file processing?

Answer 2

1. Input/Out (I/O)
2. Reading from a File
3. File name path
4. Input token
5. Valid input testing
   6.Line-based scanner
6. Scanner on strings
7. Writing output
   9.Dynamic file name input

Question 3

How do you read varies data types from the console?

Answer 3

nextInt() for integers
nextDouble() for decimals
nextLine() for full lines

Question 4

What is the difference between an absolute path and a relative path?

Answer 4

Absolute paths specify the complete file location, while relative paths are relative to the program’s current directory.

Question 5

Name four numeric methods of the Scanner class.

Answer 5

nextByte()
nextShort
nextInt()
nextDouble()

Question 6

What the difference between a physical and logical file?

Answer 6

Physical file = stored on disk
Logical file =File object used in code to access it

Question 7

what is the syntax for reading from a file using Scanner?

Answer 7

Scanner input = new Scanner(new File(‘‘mydata,txt));

Question 8

How can you count the number of words in a file?

Answer 8

Use a loop:
while (input . hasNext()) {
input .next (); count++;
}

Question 9

what is the difference between an absolute and relative file path?

Answer 9

Absolute: includes full directory structure
Relative: path from current working directory

Question 10

what is a token in Java input processing?

Answer 10

A unit of user input, separated by whitespace.

Question 11

How does Scanner treat file input?

Answer 11

As a stream of characters-token separated by whitespace.

Question 12

What does “consuming input” mean in scanner?

Answer 12

Reading a token and advancing the cursor past it.

Question 13

How can you compute change between values in a file?

Answer 13

Read current and text token, subtract to find change.

Question 14

what does the temperature program output?

Answer 14

Change in temperatures between pairs of days

Question 15

What happens if the file has fewer tokens than the loo[ expects?

Answer 15

Throws NoSuchElementException

Question 16

what are two commons Scanner exceptions?

Answer 16

NoSuchElementException -end of input
InputMismatchException - wrong token type

Question 17

what does hasNextDouble() check?

Answer 17

Whether the next token can be read as a double.

Question 18

How can safely read an int from the keyboard?

Answer 18

Check with hasNextInt() before calling nextInt()

Question 19

How do you avoid reading past the end of a file?

Answer 19

Use hasNext() or hasNext<Types>() before reading</Types>

Question 20

How can you process an unknown number of values?

Answer 20

Use while (input.hasNextDouble()).

Question 21

How does the uploaded code handle varying file lengths?

Answer 21

Use a while loop instead of fixed for.

Question 22

How do you skip non-numeric data in a Scanner?

Answer 22

Check with hasNextDouble(), else call input.next() to skip

Question 23

What does else input.next(); do in a scanner?

Answer 23

Skips over any non-numeric token safely

Question 24

What is line-based scanning?

Answer 24

Reading one full line and processing its tokes separately.

Question 25

How do you read a tokenize line?

Answer 25

String line = input.nextLine(); Scanner lineScan = new Scanner(line);

Question 26

what happens when scanner reads a line with nextLine()?

Answer 26

it reads characters until \n, including tabs and spaces

Question 27

How do you tokenize a string using Scanner?

Answer 27

Scanner scan = new Scanner("15 3.2 hello"); scan.nextInt(); // 15

Question 28

How do you count words on each line in a file?

Answer 28

Nest two scanners: one file, one for each line.

Question 29

How do you write output to a file in Java?

Answer 29

Use PrintStream or PrintWriter PrintStream out = new PrintStream (new File ("output.txt")); out.println(Hello file!);

Question 30

what happens if the output file already exists?

Answer 30

It is overwritten. Be careful!

Question 31

What is System.out in Java?

Answer 31

A printeStream object for console output.

Question 32

How do you read a filename from the user?

Answer 32

Scanner scan = new Scanner(System.in); String file = scan.nextLine();

Question 33

Name three useful methods in the File class.

Answer 33

exists() delete() length()

Question 34

What cab PrintWriter write?

Answer 34

String, char, char[], int, long, float, double, boolean

Question 35

How can you read web content using Scanner?

Answer 35

URL url = new URL("http://..."); Scanner input = new Scanner(url.openStream());