Questions

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Activity - Nested Loops

Record your participation in Piazza clicker question Lesson14 Q1

Write a pair of nested loops to print the following pattern. Don't just print "[][][][][][]"   3 times.We will do it together

[][][][][]
[][][][][]
[][][][][] 

Activity - Nested loops

Record your participation in Piazza clicker question Lesson14 Q2

Write nested loops that make the following pattern of symbols: (Note: there are no spaces) We will do this together also

#
##
###
####
#####
######

Concept - Random numbers

• Construct an object of the Random class

  • Random generator = new Random();

  • Have to import java.util.Random
• Most useful method is nextInt(int n)
  • Gets an integer between 0 (inclusive) and n (exclusive)

    int value = generator.nextInt(n);

• To get a random number between 0 and 10 (exclusive)

  • int value = generator.nextInt(10);

  • Produces one of these numbers: 0 1 2 3 4 5 6 7 8 9
• To get a random number between 1 and 10 (inclusive)

  • int value = generator.nextInt(10) + 1;

  • Produces one of these numbers: 1 2 3 4 5 6 7 8 9 10
• To get a number between 90 and 100 (inclusive)
  • First find the number of numbers in the range
  • There are 11 numbers
  • Generate the numbers 0 to 10 (11 numbers)

    generator.nextInt(11)

  • Then shift the range by 90

    generator.nextInt(11) + 90;

  • Produces one of these numbers: 90 91 92 93 94 95 96 97 98 99 100
• To get a number between 90 and 100 (exclusive)
  • First find the number of numbers in the range
  • There are 10 numbers
  • Generate the numbers 0 to 9 (10 numbers)

    generator.nextInt(10);

  • Then shift the range by 90

    generator.nextInt(10 ) + 90;

  • Produces one of these numbers: 90 91 92 93 94 95 96 97 98 99

Activity - Random numbers

Record your participation in Piazza clicker question Lesson14 Q3

Write the segment of code to generate a random integer.

• between 0 and 50 (exclusive)
• between 0 and 20 (exclusive)
• between 1 and 50 (inclusive)
• between 1 and 25 (inclusive)
• between 10 and 30 (inclusive)

Program with a bug

Record your participation in Piazza clicker question Lesson14 Q4

• Getting the application
  • Download debug Cylinder.zip
  • Unzip
  • Start the application (by double clicking the bluej.package icon
• Look at the Cylinder class
• What the Cylinder class is suppose to do
  • Models a cylinder
  • It has a constructor,
  • a method to set a new height,
  • a method to get volume,
• Run it
• Second "Expected" is incorrect.

Activity - Using the Bluej debugger - Cylinder

Record your participation in Piazza clicker question Lesson14 Q5

• Open CylinderTester class
• Set a breakpoint at line 9 (do you know how to turn on line numbers?)
• Run
• Step into the constructor
  • Notice the values of the local variables
  • Step 3 times and up to the closing brace }
  • Are the instance variables set correctly?
  • Step again - (back to the constructor in the tester)
  • Step again
• Step into getVolume
  • Step: look at the local variable areaOfCircle
  • Step: does volume look correct?
  • Step: back to the tester
  • Step one more time and look at the output
  • Step: look at expected
• Step into setHeight
  • Notice the parameter
  • Step: is the height set correctly?
  • Step: back to tester
• Step into getVolume
  • What value should be calculated?
  • What value is calculated?
  • Step: back to tester
• Continue to finish program

Activity - Using the Bluej debugger - StringIndexOutOfBounds

Record your participation in Piazza clicker question Lesson14 Q6

This program throws an exception.

Can you use the debugger to find out why?

1. Figured it out
2. Figured it but it was hard
3. Couldn't do it in the time allowed
4. Didn't know where to start

Lesson 6.2 on Udacity starting at unit 29 has a good set of videos on using the debugger where you can get more practice