GPA.java

Below is the syntax highlighted version of GPA.java from §4.4 Symbol Tables.

/******************************************************************************
 *  Compilation: javac GPA.java
 *  Execution:   java GPA
 *     (read letter grades from standard input)
 *  Dependencies: ST.java, StdIn.java,
 *
 *  % java GPA
 *  A A A A A
 *  ctl-d            (ctl-z for windows)
 *  4.0
 ******************************************************************************/

public class GPA {
    public static void main(String[] args) {
        String[] letters = { "A+", "A",  "A-", "B+", "B",  "B-", "C+", "C",  "C-", "D",  "F"  };
        double[] grades =  { 4.33, 4.00, 3.67, 3.33, 3.00, 2.67, 2.33, 2.00, 1.67, 1.00, 0.00 };

        // build the symbol table
        ST<String, Double> letterGrades = new ST<String, Double>();
        for (int i = 0; i < letters.length; i++) {
            letterGrades.put(letters[i], grades[i]);
        }

        // Read list of letter grades and compute GPA
        double sum = 0.0;
        int count = 0;
        while (!StdIn.isEmpty()) {
            String grade = StdIn.readString();
            double num = letterGrades.get(grade);
            sum += num;
            count++;
        }
        double gpa = sum / count;
        StdOut.println(gpa);
    }
}