Computer Science II

Lab 3.0 - Loops

An introduction to the loops in the Java programming language.

This is a lab used in Computer Science II (CSCE 156) for Fall 2024 in the School of Computing at the University of Nebraska-Lincoln.

Overview

Resources

• for loop tutorial: http://download.oracle.com/javase/tutorial/java/nutsandbolts/for.html
• while loop tutorial: http://download.oracle.com/javase/tutorial/java/nutsandbolts/while.html

Lab Objectives & Topics

Following the lab, you should be able to:

• Use for and while loops to implement repetition statements in a program.
• Write complex programs that require conditional logical statements and loops.

Note that the lab may involve some concepts, classes, or methods not covered (yet) in the class. You should be able to complete the lab without fully understanding them. If you have any questions about them, please feel free to ask our LAs.

Peer Programming Pair-Up

At the start of each lab, you may find a team member by yourself or randomly paired up with another student by a lab instructor. One of you will be designated the driver and the other the navigator. If you prefer to work on this lab by yourself, that is fine too. Each week you should try to alternate: if you were a driver last week, be a navigator next, etc.

Note that each student must submit the code to GradeScope for grading.

1. Getting Started

Clone this project code for this lab from GitHub in Eclipse using the URL: https://github.com/lisongxu/CSCE156-Lab-Java-Loop. Refer to Lab 1.0 for instructions on how to clone a project from GitHub.

2. Activities

2.1 Sum of Natural Numbers

Natural numbers are the usual counting numbers; 1, 2, 3, ... In this exercise, you will write several loops to compute the sum of natural numbers 1 through n where n is read from the command line. Refer to Lab 1.0 for instructions on how to use the command line argument.

1. Open the Natural.java source file. The code to read in n has been provided for you. The code to output the result has also been provided for you in the main method.

2. Write a for-loop and a while-loop in the relevant methods to compute the sum of natural numbers 1 through n and return the result.

2.2 Child Tax Credit

When filing for federal taxes, a credit is given to taxpayers with dependent children according to the following rules.

• The first (not necessarily the oldest) dependent child younger than 18 is worth a $1,000.00 credit.
• Each dependent child younger than 18 after the first child is worth a $500.00 tax credit each.

You will complete a Java program to output a table of dependent children, how much each contributes to a tax credit, and a total child tax credit. Your table should look something like the following.

Child           Amount
Tommy (14)      $1000.00
Richard (12)    $500.00
Harold (21)     $0.00
Total Credit:   $1500.00

1. Open the Child.java and ChildCredit.java source files

2. The Child class has already been implemented for you. Note how the Child class is used. Several instances of children have been created and placed into a List in the main method of ChildCredit.

   Similar to an array, a List stores elements using 0-indexing. Each one can be accessed using the get method. For example, Child c = kids.get(i) gets the i-th kid and assigns it to variable c. The total number of elements in a List can be obtained using the size() method.

3. Implement the produceReport method to compute the child tax credit(s) and output a table similar to the one above. Your method should return the grand total of the credit that is an int value.

   Each child is an instance of the Child class. Each instance has its own variables so that each child can be a different age. For example, for Child c, c.getAge() returns the age, and c.getName() returns the name.

3. Testing, Submitting, and Grading

• Test your programs locally on your computer using the provided JUnit test suites. Fix any errors and completely debug your programs.

  1. Expand the src/test/java directory, then expand the unl.soc package, and then double click on the ChildCreditTests.java file to open it.
  2. Run the test suites by clicking the usual "Play" button.
  3. Fix any errors and completely debug your programs.
  4. Expand the src/test/java directory, then expand the unl.soc package, and then double click on the NaturalTests.java file to open it.
  5. Run the test suites by clicking the usual "Play" button.
  6. Fix any errors and completely debug your programs.

• Submit the following files to GradeScope. Do not upload any other files.

  • Natural.java
  • ChildCredit.java

• Make sure that your programs pass all the tests on GradeScope. For this lab, as long as your programs pass all the tests on GradeScope, you will get full points for the lab.

• What if the test on GradeScope fails? Please test your programs locally on your computer using the provided JUnit test suite, because the test on GradeScope is exactly the same as the provided JUnit test suite. Debugging your programs on GradeScope is not recommended because GradeScope gives very limited information.*