introduction to java programming for beginners(java programming tutorials)

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MIT Africa Information Technology Initiative 1 MIT AITI Mobile Application Development in Java Lab 04: Arrays Complete these problems and show your solutions to the instructors. Be prepared to explain your code. Create a new class called GradeBook. Add a main method to GradeBook. You should put the code required to complete all the subsequent parts of this lab in the main() method. Separate each question’s output with a separator like “‐‐‐‐‐‐‐‐‐‐“ on a new line; 1. A class of students received scores of 81.4, 75.3, 90, 96.9, and 85.6. Declare and initialize an array named scores to store these values. 2. Write a loop to display the contents of scores. Make sure that your printout is readable with spaces or commas between each grade. For example: The scores are: 81.4 75.3 90 96.9 85.6 3. Compute the average and maximum scores and display it to the user. If the average grade is 85.84, and the maximum is 96.8 the output should be: Average score: 85.84 Maximum score: 96.8 4. A grade of 90 or above is an A, 80 or above is a B, 70 or above is a C, 60 or above is a D, and anything lower is an F. Write a loop to print out each student’s letter grade. The output should be of the form: Letter grades: B C A A B 5. Write code to output a histogram plot of the grade distribution using an ‘X’ to represent each person receiving that grade. For example, if there were three A’s, four B’s, two C’s, no D’s and one F, your code output should be:

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Page 1: Introduction to java programming for beginners(java programming tutorials)

MIT Africa Information Technology Initiative  1 

MIT AITI Mobile Application Development in Java Lab 04:  Arrays 

Complete these problems and show your solutions to the instructors. Be prepared to explain your code. 

Create  a  new  class  called  GradeBook.  Add  a  main  method  to  GradeBook.  You  should  put  the  code required  to  complete  all  the  subsequent  parts  of  this  lab  in  the  main()  method.    Separate  each 

question’s output with a separator like “‐‐‐‐‐‐‐‐‐‐“ on a new line; 

 

1. A  class  of  students  received  scores  of  81.4,  75.3,  90,  96.9,  and  85.6. Declare  and  initialize  an array named scores to store these values. 

 

2. Write a loop to display the contents of scores. Make sure that your printout is readable with 

spaces or commas between each grade. For example:

The scores are: 81.4 75.3 90 96.9 85.6

 

3. Compute  the  average  and maximum scores  and display  it  to  the user.  If  the  average  grade  is 85.84, and the maximum is 96.8 the output should be:  

Average score: 85.84 Maximum score: 96.8

 

4. A grade of 90 or above  is an A, 80 or above  is a B, 70 or above  is a C, 60 or above  is a D, and anything lower is an F. Write a loop to print out each student’s letter grade. The output should 

be of the form: 

Letter grades: B C A A B

5. Write code to output a histogram plot of the grade distribution using an  ‘X’  to represent each person receiving that grade. For example, if there were three A’s, four B’s, two C’s, no D’s and 

one F, your code output should be: 

Page 2: Introduction to java programming for beginners(java programming tutorials)

MIT Africa Information Technology Initiative  2 

A: XXX

B: XXXX

C: XX

D:

F: X

   

6. Using a loop, increment all the grades by an extra credit amount of 5% and print the scores out as you did in problem 3.  Be sure that the grades themselves are modified and you are not just 

displaying the modified values. 

 

7. Write code to sort and display  the contents of scores  in  increasing order. Your code should work regardless of the size of scores or its contents. Test your code on arrays of other sizes to 

make sure that it works. The output should be of the form:  

The sorted order is: 72.6 82.4 86.1 90.0 96.8

You can use an algorithm called Selection Sort.  Selection sort loops over the array and calculates the maximum element from the elements it has not sorted yet.  It has a nested structure with a for loop nested in another for loop:      for (int i = array.length; i >= 1; i--) { //find the maximum value in the array [0..i] … //swap array[i] with array[currentMaxIndex] …

}

Make sure that you understand how the above code works.  Ask us if you have any questions. 

                       

8. Make up a few other arrays of scores, and store all of these arrays in a multi‐dimensional array.  

Each of these will represent the grades for one particular person.  Then print out the 2D array of scores: 

     

Student 1: 90.1 100 50.5 40.6 80.9

Student 2: 100 89.6 90.5 52.6 99.0

    Student 3: 98.6 99 22.2 105 78