CS173: Intro to Computer Science - Expressions

Activity Goals

The goals of this activity are:
  1. To write statements that manipulate values of different numeric types
  2. To manipulate variables in a Java program
  3. To be able to apply operators appropriate to primitive data type values

Supplemental Reading

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

Warmup

How would you write a line of Java code to declare a variable containing your age as a value? What data type would this be? How might you print this value to the screen?

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: Manipulating Values with Operators

Operation
Operator
Examples
Addition
+
int x = 6 + 4;
int y = x + 2;
Subtraction
-
float z = 3.1 - 5;
Multiplication
*
double x = 5.2 * 2;
Division
/
int idiv = 5 / 2; // returns 2
double fdiv = 5 / 2.0; // returns 2.5
double y = x / 2;
Modulus
%
int remainder = 5 % 2; // returns 1
Compound Increment
++
x++; // x = x + 1;
Compound Decrement
--
x--; // x = x - 1;
Compound Addition
+=
x += 5.5; // x = x + 5.5;
Compound Subtraction
-=
x -= 2; // x = x - 2;
Compound Multiplication
*=
x *= 10.1; // x = x * 10.1;
Compound Division
/=
x /= y; // x = x / y;

Questions

  1. What is the result of dividing 6 by 4? How about dividing 6 by 4.0? How and why do these differ?
  2. How are the values of idiv (the result of the integer division operation) and fdiv (the result of the floating point division operation) different and why?
  3. What would happen if you attempt to divide by 0? Feel free to try this in the code window below!
  4. Notice the result of dividing x / 2 if x is an int? How about if x is a double or a float?
  5. Suppose you had to divide two integers, but you want the result to be stored as a floating point value. How could you ensure that this happens (there are several possibilities!)?

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!

Reflective Journal Prompt

  1. What is the binary representation of the integer value 48?
  2. What is the decimal representation of the binary value 01001?

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.

For Additional Practice

Feel free to visit these resources for additional practice exercises.