Java错误消息

Question

I am confused on the error message that I am getting while working on a Java program for class-

 ----jGRASP exec: javac -g Program3.java

Program3.java:26: error: incompatible types
    productNum = input.nextInt();
                              ^
  required: int[]
  found:    int
1 error

 ----jGRASP wedge2: exit code for process is 1.
 ----jGRASP: operation complete.

Error message in reference to below:

import javax.swing.*;
import java.util.Scanner;

public class Program3
{
public static void main(String[] args)
{
    final int NUMBER_OF_ITEMS = 5;
    int[]productNum = {1,2,3,4,5};   //array of product numbers
    double[]price = {2.98, 4.50, 9.98, 4.49, 6.87};   //array of
            price
    double quantity, product, total;
    Scanner input = new Scanner(System.in);
    System.out.print("Enter Product Number (1-5) or -1 to Quit:");
    productNum = input.nextInt();
            System.out.print("Enter Quantity:");
    quantity = input.nextDouble();
    total = product*quantity;
    System.out.print(total);
}
}

Answer 1

There are a number of errors in your code. The first being that you can't set the value of an array to an integer, you need to specify an index like: productNum[0] = input.nextInt();

Try the following code to replace your existing main function:

public static void main(String[] args)
{
    int product;
    System.out.print("Enter Product Number (1-5) or -1 to Quit:");
    Scanner input = new Scanner(System.in);
    product = input.nextInt();
    while(product != -1)
    {
        final int NUMBER_OF_ITEMS = 5; //This isn't being used for anything and could be removed
        int[] productNum = {1,2,3,4,5}; //This also isn't really being used for anything and could be removed
        double[] price = {2.98, 4.50, 9.98, 4.49, 6.87};
        double quantity, total;
        System.out.print("Enter Quantity:");
        quantity = input.nextDouble();
        total = price[product - 1] * quantity;
        System.out.println(total + "\n");
        System.out.print("Enter Product Number (1-5) or -1 to Quit:");
        product = input.nextInt();
    }
}

Answer 2

You are assigning an integer to an array of integers. It's like doing

String lol = "random text";
int random = lol;

That would raise an error because an integer can't hold the value of a string. The same thing happens in your case. You are trying to set the value of the whole array to the value of a single int . Maybe do productNum[0] = input.nextInt(); . That way, you will set the value of an int inside the array to an int. You would have to code a for loop so that you can fill in more elements of the arrays than number 0, but that wouldn't be that hard to do in my opinion.