接受和排序无限的用户输入

Question

I have only started learning java a few days ago, and this is the first language that I am trying to learn. So please, excuse my ignorance.

I am trying to create a class to accept unlimited user input (in the form of integers 5, 10, 15, 500, 10003, etc.) Then, stop accepting input when the user writes "Ok" into the command line. Then receive a prompt asking for ascending or descending. Finally, print the list of numbers in ascending or descending order, according to the user's choice.

I did not think it would be too hard to code. However, I am running into a few problems:

1. I am trying to use the scanner to accept user input and place it in an ArrayList .... However, the ArrayList will only accept one type of variable (I need to place all integer inputs in the ArrayList and display results when the string "OK" is written).

2. I do not know how to print an ArrayList so that the numbers will display on one line each in ascending or descending order.

If anyone could write me an example code or point me in the right direction, that would be much appreciated.

Answer 1

it looks like a homework :)

You check the input if it converts to int you add it to the int array,if it is equal to 'OK' you do the processing, else you ignore. Processing is about sorting your array, then loop through it and do:

System.out.println(myArray.get(i)); // print will print inline println will print and go to next line.

Answer 2

If no type is specified the ArrayList stores objects as type Object. It can mix object types (String, MyClass, Array etc. are all also of type Object). Int can be put in wrapper class Integer.

There is no type checking. Depending on your compiler / IDE settings you may get a warning: Name.java uses unchecked or unsafe operations.

This is risky - so as above answer suggests probably better to use Do loop until "OK" is entered.

Answer 3

You can use the following :

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Scanner;

public class Main {
 public static void main(String[] args) {

    System.out.println("Please enter integer numbers , write 'OK' to exit");

List<Integer>inputs=new ArrayList<Integer>();

Scanner scanner=new Scanner(System.in);
String input=scanner.next();
while(!"OK".equalsIgnoreCase(input)){
    inputs.add(Integer.parseInt(input));
    input=scanner.next();
}
if(inputs.isEmpty())
    return;
System.out.println("How would you like to sort 'ASC' or 'DSC'");
input=scanner.next();
if(input.equalsIgnoreCase("ASC")){
    Collections.sort(inputs);
}
else if(input.equalsIgnoreCase("DSC")){
    Collections.sort(inputs);
    Collections.reverse(inputs);
}
System.out.println(inputs);
}
}