CS173: Intro to Computer Science - Iteration with the while Loop

Activity Goals

The goals of this activity are:
  1. To be able to explain the uses of the while loop structure
  2. To be able to apply boolean expressions to iterative structures via the while loop

Supplemental Reading

Feel free to visit these resources for supplemental background reading material.

Warmup

How might you count the number of spaces in a String?

The Activity

Directions

Consider the activity models and answer the questions provided. First reflect on these questions on your own briefly, before discussing and comparing your thoughts with your group. Appoint one member of your group to discuss your findings with the class, and the rest of the group should help that member prepare their response. Answer each question individually from the activity, and compare with your group to prepare for our whole-class discussion. After class, think about the questions in the reflective prompt and respond to those individually in your notebook. Report out on areas of disagreement or items for which you and your group identified alternative approaches. Write down and report out questions you encountered along the way for group discussion.

Model 1: The while Loop

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public class Main {
    public static void main(String[] args) {
        boolean raining = false;
 
        while(!raining) {
            double randVal = Math.random();
            int minutes = (int) (randVal * 20);
         
            System.out.println("Play outside for " + minutes + " minutes!");
            raining = checkIfRaining(); // made up function!
        }
    }
}

Questions

  1. Draw a flow chart diagram as you did with the if statement in a prior activity ; this time, you can draw an arrow back to one of the flowchart elements to show the loop!
  2. Modify this code to implement a checkIfRaining() function that generates a random number between 1 and 10, and returns true if the number is greater than 7 (and return false otherwise).
  3. Develop an algorithm to determine if two String variables are equal.
  4. Develop a program to iterate over each character of a String and pass each character to a function that returns the letter's position in the alphabet (for example, the letter a would be position 0.

Embedded Code Environment

You can try out some code examples in this embedded development environment! To share this with someone else, first have one member of your group make a small change to the file, then click "Open in Repl.it". Log into your Repl.it account (or create one if needed), and click the "Share" button at the top right. Note that some embedded Repl.it projects have multiple source files; you can see those by clicking the file icon on the left navigation bar of the embedded code frame. Share the link that opens up with your group members. Remember only to do this for partner/group activities!

Submission

I encourage you to submit your answers to the questions (and ask your own questions!) using the Class Activity Questions discussion board. You may also respond to questions or comments made by others, or ask follow-up questions there. Answer any reflective prompt questions in the Reflective Journal section of your OneNote Classroom personal section. You can find the link to the class notebook on the syllabus.