让数组存储用户输入，然后打印最大值

Question

I am creating a program that has the user input 5 values between 0-100 and store them in an array, so that the highest value can be printed. The problem is that after the program asks the user to input the 5 values, it does not output anything after that.

import java.util.ArrayList;
import java.util.Scanner;

public class HighestGrade {

    public static void main(String[] args){
        Scanner scan =  new Scanner(System.in);
        ArrayList<Integer> scores = new ArrayList<Integer>();
        int greatest = -1;



        for (int i=0; i<5; i++) {
            System.out.print("Enter a grade (between 0 and 100): ");
            scan.nextInt();
        }

        while (scores.size()<5) {
            int input = scan.nextInt();
            if (input <= 100 && input >= 00) {
                scores.add(input);
                if(input >= greatest)
                    greatest = input;

            }
            else{
                System.out.println("Error: Make sure the grade is between 0 and 100!\nEnter a new grade!");
            }
        }

        System.out.println("\nHighest grade: "+greatest);

    }
}

Answer 1

Scores array list is empty. You forgot to insert values inside array.

    for (int i=0; i<5; i++) {
                 System.out.print("Enter a grade (between 0 and 100): ");
                  int temp = scan.nextInt();         
                if (input <= 100 && input >= 00) {
                  if( temp > greatest )
                      greatest = temp;
                 }
               else{
            System.out.println("Error: Make sure the grade is between 0 and 
                100!\nEnter a new grade!");
                } 
            }

Answer 2

You are not storing the user inputs in an array in your for loop. Also in while loop, you are again asking for user inputs. So remove your for loop. Also, there is no need to store inputs in order to just find the maximum. Only one variable is enough. Here is untested code for finding maximum.

import java.util.ArrayList;
import java.util.Scanner;

public class HighestGrade {

    public static void main(String[] args){
        Scanner scan =  new Scanner(System.in);
        int greatest = -1;
        int count = 0;
        while (count<5) {
            ++count;
            System.out.print("Enter a number: ");
            int input = scan.nextInt();
            if (input <= 100 && input >= 00) {
                if(input >= greatest)
                    greatest = input;

            }
            else{
                System.out.println("Error: Make sure the grade is between 0 and 100!\nEnter a new grade!");
            }
        }

        System.out.println("\nHighest grade: "+greatest);

    }
}

Answer 3

This is not required two loops. In the for loop you just read values. so you can simply remove it. And try like this

import java.util.ArrayList;
import java.util.Scanner;

public class HighestGrade {

  public static void main(String[] args){
    Scanner scan =  new Scanner(System.in);
    ArrayList<Integer> scores = new ArrayList<Integer>();
    int greatest = -1;

    while (scores.size()<5) {
      System.out.print("Enter a grade (between 0 and 100): ");
      int input = scan.nextInt();
      if (input <= 100 && input >= 00) {
        scores.add(input);
        if(input >= greatest)
          greatest = input;

      }
      else{
        System.out.println("Error: Make sure the grade is between 0 and 100!\nEnter a new grade!");
      }
    }

    System.out.println("\nHighest grade: "+greatest);

  }
}

Answer 4

The problem seems to be here is you are not adding the input values to the ArrayList scores at the for loop. That means the fifth input only added to the list and considered. So for this piece of code the greatest value is not printed. Only having last value as the input.

for (int i=0; i<5; i++) {
    System.out.print("Enter a grade (between 0 and 100): ");
    scores.add(scan.nextInt());
}