如果发生错误，如何提示用户重新输入值，以及如何提供继续检查工资率或退出程序的选项？

Question

Java application that inputs one salesperson's items and their corresponding amount sold for last week, then calculates and displays that salesperson's earnings.

for (int item =1; item < 5; item++){

    System.out.printf("\nHow many of item %d have you sold: ", item);
    count=input.nextInt();

    if (item == 1)      
        sales = item1* count;

    if (item == 2)
        sales2 = item2 * count;

    if (item == 3)
        sales3 = item3 * count;

    if (item == 4)
    sales4 = item4 * count;
}

Answer 1

You could keep this looping until user inputs the correct amount.You can make use of a default value which the user enters to exit the loop. Based on my understanding:

while(true)
{
       System.out.printf("\nHow many of item %d have you sold: (Enter -999 to exit)", item);
        count=input.nextInt();
        if(count== -999) //Or some default value of your choice, exit the loop
        {
              System.out.printf("Program terminated");  
              break;
        }
       for (int item =1; item < 5; item++)
       {


        if (item == 1)

          sales = item1* count;

        if (item == 2)
      sales2 = item2 * count;

        if (item == 3)
             sales3 = item3 * count;

         if (item == 4)
        sales4 = item4 * count;
        }   

}

Answer 2

A while loop is better, so you can do something like this:

While(true){     
    System.out.printf("\nHow many of item %d have you sold: ", item);
    count =input.nextInt();

    if(certain condition is reached)
      break;

    if (item == 1)
      sales = item1* count;
    else if (item == 2)
      sales2 = item2 * count;
    else if (item == 3)
      sales3 = item3 * count;
    else if (item == 4)
      sales4 = item4 * count;    
}

Then you can add a break statement somewhere within one of the control if conditions or else where within the loop to exit the loop. For example, you can use a counter to count how many times they have entered values and then break out of the loop when that is reached. It is all up to you and your requirements.