IO

Question 1

What package use for input/output?

Answer 1

import java.io*

Question 2

What buffering

Answer 2

Java will create intermediate memory called buffer which does reading and writing in the background. If not, then program would have to read one character at a time. This adds efficency

Question 3

illustration of buffering

Answer 3

Question 4

What is flushing?

Answer 4

force buffer to write to the file and wont return until its done. Ensures data is on the file before moving on

Question 5

Byte streams are for what?

Answer 5

Bytes, for binary data. Good for non-text data

Question 6

Explain character streams and what good for?

Answer 6

text files

Question 7

What are the 3 predefined streams in java

Answer 7

system.in
system.out
system.err

Question 8

Does JVM consider Console a byte device?

Answer 8

yes

Question 9

Scanner is a common Console class. T/F?

Answer 9

yes

Question 10

Scanner class.

Answer 10

import java.util.scanner

Question 11

Intro to Files

Answer 11

Question 12

T/F opening a file for writing will create a new file if it doesnt exist?

Answer 12

true

Question 13

Writnig and updating files pic

Answer 13

close files after done to save space

Question 14

What id buffered classes

Answer 14

wrapper class around i/o methods, to use buffer which adds efficeincy

Question 15

why use try with resource statments

Answer 15

auto-close the file at exit of the try

Answer 16

Question 17

recap

Answer 17

Question 18

Can you describe these byte stream wrappers?

Question 19

InputStream/outputstream topics

Answer 19

Question 20

fileinput/output stream

Answer 20

example

Question 21

bytearrayinputstream / output stream

Answer 21

treat bytes like a file

Question 22

bufferedinput/output stream

Answer 22

creates buffer support - usually perforamnce improvments

Question 23

explain pushbackinputstream

Answer 23

allows “unreading” read data. push byte back into the input stream buffer. Does not change underlying file.

does not have to pushback data you read

Question 24

whats printf()

Answer 24

specify format string then data

Question 25

does printf lineup the columns?

Answer 25

yes… cool

Question 26

datainputstream output

Answer 26

adds functionality

Question 27

endless for-loop but traps when end of file exception… kinda cool

Answer 27

Question 28

randomAccessFile explain

Answer 28

Question 29

character stream topics

Answer 29

Question 30

Reader/Writer classes

Question 31

set up our
parts inventory file so that the part number was contained in a field width of 8, the part name was
contained in a field width of 15, and the part price was contained in a field width of 10 with two values
after the decimal point.

Answer 31

output.printf( “%-8s %-15s %10.2f %n”, “P-100”, “PartNumber100”, 5.25 );
output.printf( “%-8s %-15s %10.2f %n”, “P-101”, “PartNumber101”, 2.10 );

The hyphen (-) in the string formats indicates that the respective objects will be left-justified in their
respective fields. The %n in the format strings specifies that a line separator will be written

Question 32

How write to file and append to the end of it?

Answer 32

PrintWriter output = new PrintWriter( new FileWriter( f, true) );

The “true” argument in the FileWriter constructor in the above statement allows data to be appended
to the file.