Problem 1 . (Average GPA) Write an ST client called AvgGPA that creates a symbol

Question

Problem 1. (Average GPA) Write an ST client called AvgGPA that creates a symbol table mapping letter grades to numerical scores, as in the table below, then reads from standard input a list of letter grades and computes and prints the average GPA (the average of the numbers corresponding to the grades).

$ java AvgGPA
B A - A A - B A - A - B A+ B A + A - B - B B+ B+ A C A + F
<ctrl -d >
3.2835

import edu.princeton.cs.algs4.StdIn;
import edu.princeton.cs.algs4.StdOut;
import edu.princeton.cs.algs4.ST;

public class AvgGPA {
public static void main(String[] args) {
...
}

Explanation / Answer

import java.util.HashMap;
import java.util.Scanner;

class GradeSymbolTable{
   public static void main(String[] args) {
       String letter;
       //Creating table
       HashMap<String, Double> gradeTable = new HashMap<String, Double>();
       gradeTable.put("A+",4.35 );
       gradeTable.put("A",4.00 );
       gradeTable.put("A-",3.65 );
       gradeTable.put("B+",3.35 );
       gradeTable.put("B",3.00 );
       gradeTable.put("B-",2.65 );
       gradeTable.put("C+",2.35 );
       gradeTable.put("C",2.00 );
       gradeTable.put("C-",1.65 );
       gradeTable.put("D+",1.35 );
       gradeTable.put("D",1.0 );
       gradeTable.put("D-", 0.65);
       gradeTable.put("F",0.00 );
      
       Scanner sc = new Scanner(System.in);
       // taking input
       System.out.println("Enter grade letter : ");
       letter = sc.next();
       while(!"e".equalsIgnoreCase(letter)){
           // getting gpa from table
           Double gpa = gradeTable.get(letter);
           // if entered grade letter is not valid then table will return null
           if(gpa == null)
               System.out.println("Invalid Grade Symbol");
           else
               System.out.println("GPA: "+gpa);
          
           System.out.println("Enter more grade letter or enter e/E for exit.");
           letter = sc.next();
       }
      
   }
}

/*

Output:

Enter grade letter :
A
GPA: 4.0
Enter more grade letter or enter e/E for exit.
D
GPA: 1.0
Enter more grade letter or enter e/E for exit.
e

*/

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