这是我的代码。我不确定如何使用返回值退出程序。有任何想法吗？这是我完成任务的最后一步。重要区域标有我听到了返回的消息，但是当我将main中的void更改为int时，程序会说main必须为void。

import java.util.Scanner;

public class CommissionCalculator {

public static void main(String args[]) {

// Initialize a Scanner to read input from the command line

Scanner ItemSelect = new Scanner(System.in);

double comp = 200.00;

double item1 = 239.99;

double item2 = 129.75;

double item3 = 99.95;

double item4 = 350.89;

double comm = 0.09;

int choice;

/* Note that we'll be doing this at least once and most likely multiple times...

* Prompt the user with a menu of the four items and their values (this information is included in the problem statement)

*/

System.out.println("Item\tValue");

System.out.println("1\t$239.99");

System.out.println("2\t$129.75");

System.out.println("3\t$99.95");

System.out.println("4\t$350.89");

/* Display the user's current compensation */

System.out.printf("Current compensation: $%.2f", comp);

/*

* Prompt and take input from the user (you may assume that they will only enter int values)

* They'll enter an item number (1 - 4) to record its sale or 0 to exit

*

* NOTE: THE U0SER DOES NOT ENTER PRICES DIRECTLY... THEY ENTER ITEM NUMBERS TO INDICATE WHAT WAS SOLD

* NOTE: THE USER MAY ENTER THE SAME ITEM NUMBRER MULTIPLE TIMES

*

* If the user provides invalid input (a value other than 0 - 4) display "ERROR: Invalid input!" and prompt them again

*/

do

{

System.out.print("\nPlease select an item from the " +

"list above (or enter 0 to exit): ");

choice = ItemSelect.nextInt();

{

if (choice != 1 && choice != 2 && choice != 3 && choice != 4 && choice != 0)

{

do

{

System.out.print("ERROR: Invalid Input!\n");

System.out.println("Item\tValue");

System.out.println("1\t$239.99");

System.out.println("2\t$129.75");

System.out.println("3\t$99.95");

System.out.println("4\t$350.89");

System.out.printf("Current compensation: $%.2f", comp);

System.out.print("\nPlease select an item from the " +

"list above (or enter 0 to exit): ");

choice = ItemSelect.nextInt();

if (choice == 1)

{

comp += (comm * item1);

System.out.printf("Current compensation: $%.2f", comp);

}

if (choice == 2)

{

comp += (comm * item2);

System.out.printf("Current compensation: $%.2f", comp);

}

if (choice == 3)

{

comp += (comm * item3);

System.out.printf("Current compensation: $%.2f", comp);

}

if (choice == 4)

{

comp += (comm * item4);

System.out.printf("Current compensation: $%.2f", comp);

}

if (choice == 0)

{

System.out.printf("Total Earnings: $%.2f", comp);

System.exit(0); ///

}

}while (choice != 1 && choice != 2 && choice != 3 && choice != 4 && choice != 0);

}

else

{

if (choice == 1)

{

comp += (comm * item1);

System.out.printf("Current compensation: $%.2f", comp);

}

if (choice == 2)

{

comp += (comm * item2);

System.out.printf("Current compensation: $%.2f", comp);

}

if (choice == 3)

{

comp += (comm * item3);

System.out.printf("Current compensation: $%.2f", comp);

}

if (choice == 4)

{

comp += (comm * item4);

System.out.printf("Current compensation: $%.2f", comp);

}

if (choice == 0)

{

System.out.printf("Total Earnings: $%.2f", comp);

System.exit(0);

}

}

}

}while (choice != 0);

/* After the user enters 0, display the salesperson's earnings in the format "Total earnings: $NNN.NN" and exit

* For example, if the salesperson sold two item 3s this week the final output would be "Total earnings: $217.99"

*/

if (choice == 0)

{

System.out.printf("Total Earnings: $%.2f", comp);

System.exit(0); ///

}

ItemSelect.close();

System.exit(0); ///

}

}