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Overview:

1. Write two Java classes which implement the requested functionality. The first one will implement a stopwatch, while the second one will implement an arithmetic accumulator.
2. 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.
3. 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.

Stopwatch Task:

(4pts) First, write a class named Stopwatch. This class should keep track of the time from the start (at a millisecond resolution) and be able to report the time. You will probably want to use a call from System which gives you information about the time in milliseconds. You may not use any import statements. Any data elements should be declared private, although this will not be graded. The class should implement the following methods:

• public Stopwatch() the constructor will initialize and start the stopwatch.
• public void reset() this call will restart the stopwatch.
• public double check() this call will print the elapsed time (in seconds) on the stopwatch since it was started (or the last time it was restarted). Use decimals to represent fractional amounts.
• public String toString() returns the same value as check(), except formatted as a String.

All method signatures should match the ones shown exactly.

Accumulator Task:

(5pts) Now, write a class named Accumulator. This will keep track of a (double) number which represents a running total. New values can be added to this total, and the total can be reported. Additionally, there will be methods for reading data from the input and feeding it to the accumulator. 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. The class should implement the following methods:

• public Accumulator() this constructor will initialize the accumulator with a zero total.
• public void reset() this call will reset the running total to zero.
• public void add(double val) adds val to the running total.
• public double getTotal() retrieves the current total.
• public void readNumbers(Scanner s) reads numbers from the (pre-initialized) Scanner object and adds the to the accumulator. It should read the numbers as floating point values, skipping any tokens which are not numbers, and continuing until there are no more tokens in the input.
• public void readNumbers(String str) same as above, except that the input should be read from the given String. Hint: if you read the documentation for Scanner, it should be helpful here as well.
• public String toString() returns the current total, formatted as a String.

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/labs/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:

On Mac or Linux:
In Dr Java:

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

Submission:

Submission instructions are as follows.

1. Let xxx be your lab section number (one of 213-220), and let yyyyyyyy be your GMU userid. Create the directory xxx_yyyyyyyy_E3/
2. Place all of the .java files that you've created into the directory.
3. 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
   

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