With switches as well
import java.util.Scanner;
public class Lab1
{
public static void main (String[]args)
{
double exam_score, assessment_score, total_score, real_fee=100.0, my_fee;
Scanner in = new Scanner(System.in);

int grade;
System.out.println("please enter your exam score");
exam_score = in.nextDouble();
System.out.println("please enter your assessment_ score");
assessment_score = in.nextInt();
if (exam_score>100 || assessment_score>30)
System.out.println("Enter correct scores for the components");
total_score = exam_score + assessment_score;
System.out.println("Your total score is " + total_score );
if(exam_score >= 25 && assessment_score >= 15)
{
if (total_score>=70)
System.out.println("You got 'A'");
else if (total_score>=60)
System.out.println("you got 'B'");
else if (total_score>=50)
System.out.println("you got 'c'");
else if (total_score>=40)
System.out.println("you got 'D'");
}
else
{
if (exam_score==25 && assessment_score==14)
System.out.println("You have passed but condoned. You failed in the assessment");
if (exam_score==24 && assessment_score==15)
System.out.println("You have passed but condoned. You failed in the exam");
}
System.out.println("How much have you paid as fees?");
my_fee = in.nextDouble();
if (my_fee<real_fee)
System.out.println("You cant get any Certificate. You owe fees");
if (my_fee==real_fee)
System.out.println("You have been awarded a Certificate in this course");
}
}

Switches are meant to be used to replace if/else trees.

Also the conditional where you check if the exam score is 25/24 and the assessment score is 14/15 seems ot be a little odd, is this how you're supposed tohave this according to your assignment spec?