Get matching key and value in Hashmap using Java

Enjoy that :oD (You will have better to don't save grades as pure strings :) )

public enum Grades {
    APLUS("A+"),A("A"),AMINUS("A-"),
    BPLUS("B+"),B("B"),BMINUS("B-"),
    CPLUS("C+"),C("C"),CMINUS("C-"),
    DPLUS("D+"),D("D"),DMINUS("D-"),
    EPLUS("E+"),E("E"),EMINUS("E-"),
    FPLUS("F+"),F("F"),FMINUS("F-");

    String stringVal;

    private Grades(String stringVal) {
        this.stringVal = stringVal;
    }

    @Override
    public String toString() {
        return this.stringVal;
    }
}

public static void main(String[] args) {
        HashMap<String,Grades> studentGrades= new HashMap<>();
        studentGrades.put("Alvin", Grades.APLUS);
        studentGrades.put("Alan", Grades.A);
        studentGrades.put("Becca", Grades.AMINUS);
        studentGrades.put("Sheila", Grades.BPLUS);


        try {
            //A+
            System.out.println(getGradeByStudentName("Alvin", studentGrades));
        } catch (Exception e) {
            System.out.println("Student not found");
        }

        try {
            //true
            System.out.println(isStudentGrade("Becca", Grades.AMINUS,studentGrades));
        } catch (Exception e) {
            System.out.println("Student not found");
        }

    }


    /**
     * Obtain grade by the student name
     * @param studentName name of the student
     * @param source source data
     * @return {@link Grades} value 
     * @throws Exception throws exception while student not found or data source is null
     */
    public static Grades getGradeByStudentName(String studentName,HashMap<String, Grades> source) throws Exception{
        if(source!=null && source.containsKey(studentName)){
            return source.get(studentName);
        }
        throw new Exception("Student not found in database or null input data");
    }

    /**
     * Get boolean value if given student in param has grade in param
     * @param studentName name of the student
     * @param expectedGrade expected grade
     * @param source input source data 
     * @return true, if there is student with given name and has grade in parameter, false if there is a student but has another grade
     * @throws Exception if data source is null or student with given name is not found
     */
    public static boolean isStudentGrade(String studentName, Grades expectedGrade, HashMap<String, Grades> source) throws Exception{
            Grades grade = getGradeByStudentName(studentName, source);
            return grade.equals(expectedGrade);
    }

FYI For iterate over Keys and values in hashmap you can use following

HashMap<String, String> mapName = new HashMap<>();

        for (String actualKey : mapName.keySet()) {
            //eg. String value = mapName.get(actualKey);
        }

        for (String actualVal : mapName.values()) {

        }