Lab 5: Loops

For the TA
- In this lab, students must write 2 for-loops that print figures using letters
- The lab assignment is self-explanatory and your job is to assist students (help them find/show them the answers) when they have questions.
Lab goals
- In this lab you will learn to write for-loops to make text based drawings.
  Please, make sure that you have added the honor code statement at the top of your Java file:
  The deadline for completing this lab assignment is midnight, today.
Preparation: Create your ~/cs170/lab5/, and copy files
- Copy-and-paste these terminal commands:
  In this lab, we will use gedit and javac (not BlueJ !).
  (You could use BlueJ, but you must figure out how to compile and run the program on your own.)

Overview of the provided methods

Look at the program Sample.java with gedit:

You are provided with the following method:

indentCharLine(i, c, n):

This method will first print i spaces (i.e., indents i positions)
Then, it prints the character c (given as input of the method), n times (n is also an input parameter)
Finally, it prints NEWLINE (to end the current line)

Example:

indentCharLine(4, 'A', 6) will print: ____AAAAAA indentCharLine(6, 'X', 3) will print: ______AAA (I use _ to represent a BLANK SPACE)

The Sample.java program contains a main() method that shows you how to use the method indentCharLine() to draw a square:

public static void main(String[] args) { int i; /* ----------------------------------------- Make sure user provides 1 argument ----------------------------------------- */ if ( args.length != 1 ) { System.err.println("Error: Program needs 1 integer as input"); System.exit(1); } /* ----------------------------------------- Convert first argument to integer ----------------------------------------- */ int n = Integer.parseInt( args[0] ); /* ----------------------------------------------- Use indentCharLine() to print a nxn square Print n rows of character 'X' of width n ----------------------------------------------- */ for ( i = 0; i < n; i++ ) { indentCharLine(1, 'X', n); } }

You can see the result by compiling and executing the program Sample.java:

javac Sample.java java Sample 3 Output: XXX XXX XXX

Lab Assignment - Part 1: complete program Triangle1.java

Edit the Triangle1.java program that is provided for this lab:

Complete the main() method:

/* ************************************************** +---------+ | TODO: | +---------+ Use a for-loop to print the following triangle: X ^ XX | ... | n rows XXXX | XXXXX | XXXXXX v <----> base = n ++++ Note: the body of the for-loop uses the method indentCharLine() !!! ************************************************** */

Note:

Make use of the method indentCharLine() inside the for-loop to make your loop simple !!!

After completing the main() method, you can compile and run the program with these commands:

javac Triangle1.java java Triangle1 7

and if correct, you should see this output:

X XX XXX XXXX XXXXX XXXXXX XXXXXXX

Lab Assignment - Part 2: complete program Triangle2.java

Edit the Triangle2.java program that is provided for this lab:

Complete the main() method:

/* ********************************************************* +---------+ | TODO: | +---------+ Use a for-loop to print the following triangle: X ^ XX | ... | n rows XXXX | XXXXX | XXXXXX v <----> base = n ++++ Note: the body of the for-loop uses the method indentCharLine() !!! ********************************************************* */

Note:

Make use of the method indentCharLine() inside the for-loop to make your loop simple !!!

After completing the main() method, you can compile and run the program with these commands:

javac Triangle2.java java Triangle2 7

and if correct, you should see this output:

X XX XXX XXXX XXXXX XXXXXX XXXXXXX

Turn in
- You must turn in your work by enter these terminal commands:
  before midnight today.
  
  For the Lead TA: