I have a java program homework problem, i don\'t know how to use the HashMap, pl

Question

I have a java program homework problem, i don't know how to use the HashMap, please help.

// Grades.java

import java.util.HashMap;

public class Grades

{

public static void main(String[] args)

{

int N = 0; // number of students

double totalGPA = 0.0; // total GPA

HashMap<String, Double> map = new HashMap<String, Double>();

// TBD

map.put("A", new Double(4.33));

map.put("A-", new Double(3.67));

map.put("B+", new Double(3.33));

map.put("B", new Double(3.00));

map.put("B-", new Double(2.67));

map.put("C+", new Double(2.33));

map.put("C", new Double(2.00));

map.put("C-", new Double(1.67));

map.put("D", new Double(1.00));

map.put("F", new Double(0.00));

System.out.println(totalGPA / N);

}

}

Explanation / Answer

// Grades.java
import java.util.*;
public class Grades
{
    public static void main(String[] args)
    {
int N = 0; // number of students
double totalGPA = 0.0; // total GPA
HashMap<String, Double> map = new HashMap<String, Double>();
// TBD
map.put("A", new Double(4.33));
map.put("A-", new Double(3.67));
map.put("B+", new Double(3.33));
map.put("B", new Double(3.00));
map.put("B-", new Double(2.67));
map.put("C+", new Double(2.33));
map.put("C", new Double(2.00));
map.put("C-", new Double(1.67));
map.put("D", new Double(1.00));
map.put("F", new Double(0.00));

for(String key: map.keySet()) {
System.out.println( "Key : "+ key + " -- value: " + map.get(key));
totalGPA+= map.get(key);
N++;
}

System.out.println("average grade is " + totalGPA / N);
    }

}

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