Question

Question 7                                                                                                                  6 Marks

1. Given the following code, use lambdas and streams to calculate and display the number of marks greater than or equal to 50 (i.e. the total number that have passed).                                                                                                        (1 mark)

public static void main(String[] args) {

    int[] marks = {10, 53, 65, 49, 46, 95, 81, 45, 72, 85};

         //use lambdas and streams to work out how many

         // marks are >= 50 and display the result.

         <part (a) to complete>

      }

      Output should be similar to the following:

    The number of marks greater than or equal to 50 = 6

2. The following is the class diagram for the Result class used in this question.

Given the starting point for the code below, use lambdas and streams to complete the main method as follows:

1. Write a Predicate called supplementary that returns true if the mark is in the supplementary range (>=45 and <50) and false if the mark is not in this range.                                                                                              (1 mark)
2. Make use of the predicate from part (i) to display all the result records (student id and mark) with marks in the supplementary range     
3. Use lambdas and streams to calculate and display the average mark.

    

In the answer template complete the code for parts (i) to (iii) where you see <to be completed> in the code below:

public class StreamQuestion {

    public static void main(String[] args) {

        Result[] results = {new Result("S123345", 10),

                            new Result("S678901", 53),

                            new Result("S778901", 65),

                            new Result("S878901", 49),

                            new Result("S078901", 81),

                            new Result("S688901", 45),

                            new Result("S698901", 72),

                            new Result("S679901", 46),

                            new Result("S678911", 72),

                            new Result("S678912", 85)};

       

        List<Result> resultList = Arrays.asList(results);       

                                  

       //(i) Write the code for the supplementary predicate

        <Part (i) To be completed>

   // (ii) using the predicate (and lambdas and streams),  

   // display the student id and mark for all results in

   // the supplementary range

       <Part (ii) To be completed>

   // (iii) using lambdas and streams calculate and display

   // the average mark           

       <Part (iii) To be completed>

    }  

The output generated should be similar to the following:

Supplementary List:

<S878901 49>

<S688901 45>

<S679901 46>

Average Mark: 57.80

Answer 1

Please find the answer below.
Please do comments in case of any issue. Also, don't forget to rate the question. Thank You So Much.

Main.java

package staticClass;

import java.util.Arrays;

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

       int[] marks = {10, 53, 65, 49, 46, 95, 81, 45, 72, 85};
       int num=0;
       //use lambdas and streams to work out how many

       // marks are >= 50 and display the result.
      
       num=(int) Arrays.stream(marks).filter(e->e>50).count();
      
       System.out.println("The number of marks greater than or equal to 50 = "+num);
   }
}

output

2)

StreamQuestion.java

package staticClass;

import java.util.Arrays;
import java.util.List;
import java.util.function.Predicate;

class Result{
   private String id;
   private int mark;
   public Result(String id, int mark) {
       super();
       this.id = id;
       this.mark = mark;
   }
   public String getId() {
       return id;
   }
   public void setId(String id) {
       this.id = id;
   }
   public int getMark() {
       return mark;
   }
   public void setMark(int mark) {
       this.mark = mark;
   }
   @Override
   public String toString() {
       return "<" + id + " " + mark + ">";
   }
  
  

}
public class StreamQuestion {

   public static void main(String[] args) {

       Result[] results = {new Result("S123345", 10),

               new Result("S678901", 53),

               new Result("S778901", 65),

               new Result("S878901", 49),

               new Result("S078901", 81),

               new Result("S688901", 45),

               new Result("S698901", 72),

               new Result("S679901", 46),

               new Result("S678911", 72),

               new Result("S678912", 85)};

       List<Result> resultList = Arrays.asList(results);   

       //(i) Write the code for the supplementary predicate
      
       Predicate<Result> lesserthan = i -> (i.getMark()>=45 && i.getMark()<50);
      
       // (ii) using the predicate (and lambdas and streams),

       // display the student id and mark for all results in

       // the supplementary range
      
       System.out.println("Supplementary List:");
       resultList.stream().filter(lesserthan).forEach(p->System.out.println(p));
      
       // (iii) using lambdas and streams calculate and display
       double sum=resultList.stream().mapToInt(i -> i.getMark()).sum();
       double avg = sum/resultList.size();
       System.out.printf("Average Mark: %.2f",avg);
       // the average mark   

   }
}

output