Laboratory: Simple Input and Output
Exercise 1: Basic Interaction
Write and test a main class called Greet that prompts the
user for a name, reads a name from the keyboard, and prints a greeting
to the screen. Your output should resemble the following:
What is your name? Sam
Have a nice day Sam!
To type a response, you may need to click in the console area of the
Eclipse window.
Exercise 2: Creating a File
a. Write and test a main class called DumpInfo that
prints the following three lines to the screen.
- Your name
- Your email address
- Your favorite color
b. Update DumpInfo so that it instead creates a file
and dumps the information to that file.
c. Predict what will happen when you have DumpInfo.java
write to a file that already exists. (For example, if you run it a
second time.)
d. Check your prediction experimentally.
e. Predict what will happen when you modify DumpInfo.java
to write to a file in a classmate's directory.
f. Check your prediction experimentally.
Exercise 3: Reading a File
a. Write and test a main class called ShowInfo that reads a file
of three lines named info and prints each line preceeded
by a category prompt (Name, Email, Color). For example, if the file contains
J. Doe
doej@gmail.com
plaid
the output on the screen should be
Name: J. Doe
Email: doej@gmail.com
Fave Color: plaid
b. Modify info using gedit and verify that
ShowInfo continues to work correctly.
Exercise 4: Insufficient Input
a. What do you expect to happen when you run ShowInfo
if info contains only two lines (e.g., doesn't contain a color)?
b. Check your answer experimentally.
c. What do you expect to happen when you run ShowInfo
if info does not exist?
d. Check your answer experimentally.
e. What do you expect to happen when you run ShowInfo
using a file in a classmate's directory?
f. Check your answer experimentally.
Exercise 5: Copying Parts of a File
Write and test a main class, CopyTwoLines, that copies
the first two lines from a file named source and places
them in a file named destination.
Exercise 6: Copying Parts of a File, Revisited
Write a test a main class, NewCopier, that prompts the
user for the name of two files and copies the first two lines from the
first file to the second file.
Exercise 7: Rewinding a File"
Write a short main class, ReadTwice, that prompts
the user for a file, builds a BufferedReader for the
file, sets a mark, reads the first line from the file, resets the
BufferedReader, and reads again.
For Those With Extra Time
If you finish the lab early, you may want to try some or all of the following.
Extra 1: Marks and Keyboard Input
Determine whether you can use mark and reset
for input taken from the keyboard in addition to input taken from a
file.
Determine whether you can place more than one mark in a file.
Determine what happens if you read more than readAheadLimit
characters between calls to mark and reset. Does
the size of readAheadLimit make a difference (e.g., do you
get the same behavior for small and large readAheadLimit if
you read only two characters beyond that limit)?
