(Java) How to Keep Track of Numbers Entered by User for Determining Min and Max

问题

I have a homework assignment that is asking me to use an input dialog to ask the end user to enter a number, parse that String to an int, and then use a confirm dialog to ask if the user wants to enter another number. If they click yes, the program loops, and once they hit no, it takes all of the entered numbers and determines the min and max. How do I keep track of all the entered numbers without declaring multiple variables to hold them (since the user can technically enter an infinite amount of numbers)?

I'm very new to programming. I've been scouring my textbook, and I've browsed Stack Overflow to find my specific problem and haven't found anything, at least in Java.

    {
        int yes = JOptionPane.YES_OPTION;

        do
        {
            String numberstring = JOptionPane.showInputDialog("Enter a "
                    + "number: ");
            int number = Integer.parseInt(numberstring);

            yes = JOptionPane.showConfirmDialog(null, "Do you want to enter"
                    + " another number?", "MinMax", JOptionPane.YES_OPTION);
        }
        while (yes == JOptionPane.YES_OPTION);

        JOptionPane.showMessageDialog(null, "The min is " + min + " and the"
                + " max is " + max);
    }

I'm not exactly receiving any errors, I just have no idea how to hold a possibly infinite amount of entries from the user since the program loops until the user clicks "no".

回答1:

You can do it as follows:

{
    int yes = JOptionPane.YES_OPTION;
    List<Integer> list=new ArrayList<Integer>();

    do
    {
        String numberstring = JOptionPane.showInputDialog("Enter a "
                + "number: ");
        int number = Integer.parseInt(numberstring);

        list.add(number);

        yes = JOptionPane.showConfirmDialog(null, "Do you want to enter"
                + " another number?", "MinMax", JOptionPane.YES_OPTION);
    }
    while (yes == JOptionPane.YES_OPTION);

    int min = list.get(0), max = list.get(0);
    for (int i = 1; i < list.size(); i++) {
        if (min > list.get(i))
            min = list.get(i);
        if (max < list.get(i))
            max = list.get(i);
    }

    JOptionPane.showMessageDialog(null, "The min is " + min + " and the"
            + " max is " + max);
}

回答2:

Create minimum and maximum variables, and update them every time user inputs a new number:

int min = Integer.MAX_VALUE, max = Integer.MIN_VALUE;
...
int number = Integer.parseInt(numberstring);
min = Math.min(number, min);
max = Math.max(number, max);

回答3:

If you really want to keep all the numbers, you could create a list and keep adding entered numbers to it:

List<Integer> allNumbers = new LinkedList<>();
do {
    String numberstring = JOptionPane.showInputDialog("Enter a number: ");
    int number = Integer.parseInt(numberstring);
    allNumbers.add(number);
    yes = JOptionPane.showConfirmDialog
              (null, 
               "Do you want to enter another number?",
               "MinMax",
               JOptionPane.YES_OPTION);
} while (yes == JOptionPane.YES_OPTION);

However, you should note this is a very inefficient approach - you don't really need all the numbers, just the minimum and the maximum, which you could calculate as you go, and avoid storing all these numbers:

int max = Integer.MIN_VALUE;
int min = Integer.MAX_VALUE;

do {
    String numberstring = JOptionPane.showInputDialog("Enter a number: ");
    int number = Integer.parseInt(numberstring);
    max = Math.max(max, number);
    min = Math.min(min, number);
    yes = JOptionPane.showConfirmDialog
              (null, 
               "Do you want to enter another number?",
               "MinMax",
               JOptionPane.YES_OPTION);
} while (yes == JOptionPane.YES_OPTION);

来源：https://stackoverflow.com/questions/58366328/java-how-to-keep-track-of-numbers-entered-by-user-for-determining-min-and-max

标签

java

loops

max

min

joptionpane