GPA.java

Below is the syntax highlighted version of GPA.java from §3.1 Elementary Symbol Tables.

/******************************************************************************
 *  Compilation:  javac GPA.java
 *  Execution:    java GPA < input.txt
 *  Dependencies: ST.java
 *
 *  Create a symbol table mapping letter grades to numerical
 *  scores, then read a list of letter grades from standard input,
 *  and print the GPA.
 *
 *  % java GPA
 *  A- B+ B+ B-
 *  GPA = 3.25
 *
 ******************************************************************************/

public class GPA {
    public static void main(String[] args) {

        // create symbol table of grades and values
        ST<String, Double> grades = new ST<String, Double>();
        grades.put("A",  4.00);
        grades.put("B",  3.00);
        grades.put("C",  2.00);
        grades.put("D",  1.00);
        grades.put("F",  0.00);
        grades.put("A+", 4.33);
        grades.put("B+", 3.33);
        grades.put("C+", 2.33);
        grades.put("A-", 3.67);
        grades.put("B-", 2.67);


        // read grades from standard input and compute gpa
        int n = 0;
        double total = 0.0;
        for (n = 0; !StdIn.isEmpty(); n++) {
            String grade = StdIn.readString();
            double value = grades.get(grade);
            total += value;
        }
        double gpa = total / n;
        StdOut.println("GPA = " + gpa);
    }
}