NoSuchElementException and premature closure of scanner

I have made a program that reads 5 integers and outputs its polarity(positive or negative), its type(odd or even). Used Scanner.nextLine() to read the input as string and split it with .split("\s+") and phrased every entry into an integer in a for loop. For error handling when I tried to enter an non integer input such as a character the scanner.nextLine() gets closed prematurely and throws a NoSuchElementException.

Here's my full code:

import java.util.Scanner;

public class Checker {
    public static class outputVal{
        private String polarity, type;

        public outputVal(String x, String y){
            this.polarity = x;
            this.type = y;
        }
        public String getPolarity() {
            return polarity;
        }
        public String getType() {
            return type;
        }
    }
    public static int[] getInput(){
        Scanner scanner = new Scanner(System.in);
        try{
            String input = scanner.nextLine();
            String [] inputTokens  = input.split("\\s+");
            int [] intTokens  = new int[5];
            for(int i=0; i<inputTokens.length; i++){
                intTokens[i] = Integer.parseInt(inputTokens[i]);
            }
        return intTokens;
        }
        catch(NumberFormatException e){
            System.out.println("[ERROR] Enter only integer!!!");
            return new int[0];
        }
        finally{
            scanner.close();
        }
        
    }

    public static String checkPolarity(int x){
        if(x== 0){
            return "Zero";}
        else{
        return x>0 ? "Positive" : "Negative";
        }   
    }

    public static String evenOdd(int x){
        return x%2 ==0 ? "Even" : "Odd";  
    }   

    public static String checkValue(int[] x){
        if(x.length <2) return "N/A";
        if(x[0]==x[(x.length)-1]){
            return "Equal";}
        else{
        return x[0]>x[(x.length)-1] ? "Greater" : "Lesser";
        }   
    }
    
    public static void main(String[] args) {
        int[] input = new int[5];

        while(input.length == 0){
            System.out.print("Enter five integers: ");
            input = getInput();
            if(input.length == 0 )System.out.println("[ERROR] Inappropriate Data. Please try again.");
        }
        
        if(input.length<5) {
            System.err.println("[ERROR] Insufficient Data. Exitting....");
            return;
        }

        outputVal[] output = new outputVal[input.length];

        for(int i= 0; i<input.length; i++){
            output[i] = new outputVal(checkPolarity(input[i]),evenOdd(input[i])); 
        }

        for(int i= 0; i<input.length; i++){
            System.out.printf("The number '%d' is %s, %s %n",input[i],output[i].getPolarity(),output[i].getType());
        }

        System.out.printf("%nThe first number is %s than the last number", checkValue(input));
    }
}

....................

Your code has two small problems:

• 1. every time we call the xx method, the Scanner object is instantiated, this is not desirable behavior, but there is something worse, the finally method closes the Scanner and with it System.ini is closed, the Scanner can be instantiated again, System.ini cannot, it is the message you receive.

This is solved by putting the instantiation in the start method (formerly main), as well as the call to close().

public int[] getInput() {
   try {
      String input = scanner.nextLine();
      String[] inputTokens = input.split( "\\s+" );
      int[] intTokens = new int[ 5 ];
      for( int i = 0; i < inputTokens.length; i ++ ) {
         intTokens[ i ] = Integer.parseInt( inputTokens[ i ] );
      }
      return intTokens;
   }
   catch( NumberFormatException e ) {
      System.out.println( "[ERROR] Enter only integer!!!" );
      return new int[ 0 ];
   }
}

• 2. In the start method, the while condition is always "false", since a few lines before we created the array with size "5", for it to work, we simply instantiate the array with size "0", with the call to getInput() a new array will be created and assigned to xx, meaning that the initial value only serves to satisfy the while condition.

public void start() {
   int[] input = new int[0]; 
   while(input.length == 0 ){
      System.out.print( "Enter five integers: " );
      input = getInput();
      if( input.length == 0 ) {
         System.out.println( "[ERROR] Inappropriate Data. Please try again." );
      } 
   }

   if( input.length < 5 ) {
      System.err.println( "[ERROR] Insufficient Data. Exitting...." );
      return;
   }

   outputVal[] output = new outputVal[ input.length ];

   for( int i = 0; i < input.length; i ++ ) {
      output[ i ] = new outputVal( checkPolarity( input[ i ] ), evenOdd( input[ i ] ) );
   }

   for( int i = 0; i < input.length; i ++ ) {
      System.out.printf( "The number '%d' is %s, %s %n", input[ i ], output[ i ].getPolarity(), output[ i ].getType() );
   }

   System.out.printf( "%nThe first number is %s than the last number", checkValue( input ) );
   scanner.close();
}

public static void main( String[] args ) {
   new Checker().start();
}