LAB EXERCISE 3 Solution

The objective of this lab is to be able to build simple classes, including designing the needed data structure and implementing the requested behaviors; also to be able to effectively use Java methods for processing input (via the Scanner class).







OVERVIEW:




Write two Java classes which implement the requested functionality. The first one will implement a student grade, while the second one will implement an input filter which splits intput into floating points, integers, and ordinary strings.
Download and use a tester module to ensure that your programs are correct. The programs can also be tested using Dr Java's interactive window.
Prepare the assignment for submission and submit it



This is a lab exercise on which collaboration (including discussing the solution on Piazza or searching online sources) is explicitly permitted.




It is still in your interest to understand and prepare your final submission yourself.




GRADE TASK:




(4pts) First, write a class named Grade. This class should keep track of a student's grade. The grade itself will be stored as a floating point number, but it should also be able to produce a corresponding letter grade. You may not use any import statements. Any data elements should be declared private, although this will not be graded. If you think it is necessary you may include helper methods of your own. The class should implement the following public methods:




public Grade() the constructor will initialize the grade to 100.0.







public Grade(double grade) the constructor will initialize the grade to the given value. If a grade less than zero is passed in, then the value should default to zero instead.




double getGrade() this getter method will return the student's grade.




void setGrade(double grade) this setter method will set a new value of the grade. If a grade less than zero is passed in, then the value should be ignored and the original kept instead.




public String toString() returns the letter grade corresponding to the numerical grade. The scale is: "A" for 90 and above; "B" for grades 80 and above but below A; "C" for grades 70 and above but below B; "D" for 60 and above but below C; "F" for all other grades.







All method signatures should match the ones shown exactly.




INPUT SPLITTER TASK:




(5pts) Now, write a class named InputSplitter. This class will take input from the keyboard (using a Scanner) and split the incoming tokens into integers, floating point numbers, and strings. The incoming tokens will be added to one of three accumulators which start out at zero, and which keep a running total.




Thus, the class will have an accumulator for integers. It starts out with the value zero. Every time another integer is read in, it is added to the integer accumulator. The accumulator keeps a running total of all the integers which have been seen so far. Likewise, there is an accumulator for floating point values. It starts at zero, but adds every floating point value which is seen. Finally, there is a string accumulator. It starts out as an empty string, but appends to the string every time another string token is read. Your class will need to be able to decide the type of each input token (hint: a Scanner has the methods hasNextInt(), hasNextDouble(), and hasNext()) as well as to keep track of the running totals (hint: you can use instance variables).




The only import statement you may use in this implementation is the Scanner class. Any data elements should be declared private, although this will not be graded. If you think it is necessary you may include helper methods of your own. The class should implement the following public methods:




public InputSplitter() this constructor will initialize the three accumulators as well as the Scanner which is used for input. public void next() read the next token, and print its type and value. This method will use the input Scanner object which was initialized earlier to read the next token from the input. Depending on the type of the input token, method will print the value of the token in one of the following three formats:




integer: 1







double: 2.0







string: abc




https://mymasonportal.gmu.edu/bbcswebdav/pid-8880354-dt-content-rid-158214028_1/courses/16097.201910_16098.201910_16099.201910_16100.201910_16122.… 1/3

2/8/2019 Lab Exercise-3 for CS 211 / Spring 2019







In addition to the printed output, the value will be added (appended, in the case of a string) to the accumulator for the specific type.




public int getIntTotal() retrieves the total value summed in the integer accumulator.




public double getDoubleTotal() retrieves the total value summed in the floating point accumulator.




public String getStringTotal() retrieves the complete value concatenated in the string accumulater.




public String toString() returns the current contents of each of the three accumulators as a single string in the following format:







integer: 1 double: 2.0 string: abc




Below is a sample run demonstrating how the class would function using the following input:




1 abc 2.0 3 def 4.0 6 7 xyz 5.5







InputSplitter i = new InputSplitter();



System.out.println(i);



integer: 0 double 0.0 string:




i.next(); integer: 1



System.out.println(i); integer: 1 double 0.0 string:



i.next();



string: abc




i.next(); double: 2.0



System.out.println(i);



integer: 1 double 2.0 string: abc




i.next(); integer: 3



System.out.println(i);



integer: 4 double 2.0 string: abc




i.next(); string: def



System.out.println(i);



integer: 4 double 2.0 string: abcdef




i.next(); double: 4.0



System.out.println(i);



integer: 4 double 6.0 string: abcdef




i.next(); integer: 6



i.next(); integer: 7



i.next(); string: xyz



i.next(); double: 5.5



System.out.println(i);



integer: 17 double 11.5 string: abcdefxyz




System.out.println(i.getIntTotal());



17




System.out.println(i.getDoubleTotal()); 11.5



System.out.println(i.getStringTotal()); abcdefxyz



TESTING:




Download the following (if you don't already have it):




https://mason.gmu.edu/~iavramo2/classes/cs211/junit-cs211.jar







https://mason.gmu.edu/~iavramo2/classes/cs211/s19/E3tester.java







This is a unit tester which is what we will use to test to see if your classes are working correctly.




When you think your classes are ready (you can try them even without the tester), do the following from the command prompt to run the tests.









On Windows:







javac -cp .;junit-cs211.jar *.java




java -cp .;junit-cs211.jar E3tester




On Mac or Linux:







javac -cp .:junit-cs211.jar *.java




java -cp .:junit-cs211.jar E3tester




In Dr Java:




open the files, including E3tester.java, and click the Test button.







SUBMISSION:




Submission instructions are as follows.




Let xxx be your lab section number and let yyyyyyyy be your GMU userid. Create the directory xxx_yyyyyyyy_E3/



Place all of the .java files that you've created into the directory.



Create the file ID.txt in the format shown below, containing your name, userid, G#, lecture section and lab section, and add it to the directory. Your directory should contain three files total.



Full Name: Donald Knuth




userID: dknuth




G#: 00123456




Lecture section: 004




Lab section: 213




compress the folder and its contents into a .zip file, and upload the file to Blackboard.



























































































































https://mymasonportal.gmu.edu/bbcswebdav/pid-8880354-dt-content-rid-158214028_1/courses/16097.201910_16098.201910_16099.201910_16100.201910_16122.… 3/3