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. We will do it together

1 
1 2 
1 2 3  
1 2 3 4
1 2 3 4 5 
1 2 3 4 5 6  

Activity - Nested loops

Record your participation in Piazza clicker question Lesson14 Q2

Write nested loops that make the following pattern of brackets: (Note: there are no spaces)

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

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

 

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 rage 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. Unless otherwise stated, the range is inclusive of the first number and exclusive of the last number

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

 

Program with a bug

Record your participation in Piazza clicker question Lesson14 Q4

• Getting the application
  • Download debug MagicPotion.zip
  • Unzip
  • Start the application (by double clicking the bluej.package icon
• Look at the MagicPotion class
• What the MagicPotion class is suppose to do
  • A MagicPotion is a cylinder filled with a magic potion that has a set cost per cubic centimeter
  • It has a constructor,
  • a method to set a new height,
  • a method to get volume,
  • a method to get the cost.
• Run it
• Third "Expected" is incorrect.

 

Activity - Using the Bluej debugger - MagicPotion

Record your participation in Piazza clicker question Lesson14 Q5

• Open MagicPotionTester 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 getCost
  • Will the correct value be returned?
  • Step back to the tester
  • Step: what is printed?
  • Step: what is the expected value
• Step into setHeight
  • Notice the local variable
  • Step: is the height set correctly?
  • Step: back to tester
• Step into getCost
  • 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 youuse 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