Build a Complete Java Project

Hello students, welcome to Kwickprep. Writing one small program is easy. But how do you build a complete project, with many classes, that really works and impresses the examiner? Today we will build a student report card project, from choosing the problem, to design, coding, testing and presenting it.

Every good project goes through five stages. First, we choose a problem and analyse it, which means understanding it fully. Second, we design the classes and methods on paper. Third, we write the code one piece at a time. Fourth, we test each piece before moving to the next. Fifth, we document and present the project.

How do you choose a good problem? Pick a real problem that you understand well. Make it small enough to finish in the time you have, because a finished small project beats a half done big one. It should have clear inputs and clear outputs. Good ideas are a report card, a canteen bill, or a library book issue system.

Analysis means writing down exactly what the program must do. The input is each student's name, and marks in three subjects. The process is to find the total, the average, shown as avg, and the grade. The output is a report for each student, and the name of the topper. The rules say marks must be from zero to one hundred, so anything else is rejected.

Now the design. A simple trick helps you find classes. Nouns in the problem, like student and report, often become classes. The data about each thing, like a name and marks, becomes its fields. Actions, like find the total, become methods. And each class should do one clear job only.

Here is our design, as a simple table. The Student class stores a name and an array of marks, and has the methods total and grade. The Report class stores an array of Student objects, and can print all reports and find the topper. The App class only has main, which reads input and starts everything.

We turn the design straight into a skeleton. A skeleton has the class, its fields and its method headings, but the method bodies are still empty, so it will not compile yet. The constructor stores the name and marks. Total will return an int, and grade will return a char. Now we fill in the bodies, one stage at a time.

Coding in stages means you never write everything at once. Write one method at a time. Test it straight away with values you can check by hand. Only when it works, start the next method. And keep a copy of the last working version, so a new mistake never ruins everything.

Stage one tests the total method alone. The for each loop takes every mark x from the array, and adds it to t. We test it with eighty, seventy two and ninety one. By hand, that adds up to two hundred forty three. The program prints two hundred forty three, so stage one is done.

Stage two adds the grade method. An average of seventy five or more is A, fifty or more is B, and anything lower is C. Pause and predict. What does grade of exactly seventy five return? It returns A, because greater than or equal to includes seventy five. Testing the exact boundary catches the most common mistake, using greater than by accident.

Write every test in a test log, because it becomes part of your documentation. Total with eighty, seventy two and ninety one gave two hundred forty three, which is correct. Grade with seventy five gave A. Grade with forty nine gave C. And marks of one hundred five were rejected, as our rules say.

Stage three finds the topper among many students. Array n holds three names, and array t holds their totals. We assume the first student is the topper, so p is zero. Then we check the others, one by one. If a total is higher than the best so far, p moves to that position. At the end we print the name at p, and it is Aman.

Input is added in the last stage, not the first. While building, use fixed test values, so you do not type marks again and again. When the logic works, add Scanner input. Check the input, and reject marks below zero or above one hundred. Finally, run the whole program again on every case in your test log.

Documentation explains your project to someone else. One common part is a variable description table. Name is a String that stores the student's name. Marks is an int array, holding marks in three subjects. List is an array of Student objects. Top is the Student with the highest total.

The code itself must be documented too. Put a comment at the top, with the project's purpose, your name and the date. Put a short comment above each method, saying what it does. Use meaningful names, like total, instead of t one. And keep the indentation neat, with one statement on each line.

Your project report follows the same order as your work. Begin with the problem statement and the analysis. Then show the class design table and the algorithm. Next comes the program code, with comments. Then the sample output and the test log. End with limitations, like no saving to a file, and ideas for the future.

Let us revise the whole journey. Choose a small, real problem, and analyse its input, process and output. Design classes from the nouns, and methods from the actions. Code and test one stage at a time, keeping a test log. Then document your code, and present the project in the same order that you built it.