How do I validate an integer input number to be only from 1 to 8 when "enter an option" or-CodePudding

while (option < 1 || option > 8) {

    System.out.print("Invalid input! Enter an option>");

    option = scanner.nextLine();

}

This is the error I'm getting when I validate:

error: bad operand types for binary operator '<'

while (option < 1 || option > 8) {

               ^

       first type:  String

       second type: int


error: bad operand types for binary operator '>'

 while (option < 1 || option > 8) {

                           ^

  first type:  String

  second type: int

2 errors

BELOW IS THE CODE:


import java.util.Scanner;

public class Demo {



public static void main(String[] args) {



Playlist play = new Playlist();

String option = "";

Scanner scanner = new Scanner(System.in);



String songName, albumName, artistName;

int length;



Song currentSong = null;



menu();

System.out.print("Enter an option> ");

option = scanner.nextLine();



while (!option.equals("8")){



switch (option){



case "1":

System.out.print("What is the name of the Song> ");

songName = scanner.nextLine();

System.out.print("What is the name of the Album> ");

albumName = scanner.nextLine();

System.out.print("What is the name of the Artist> ");

artistName = scanner.nextLine();

System.out.print("What is the length of the song in seconds> ");

length = scanner.nextInt();

play.insertSong(new Song(songName, artistName, albumName, length));

System.out.println( "\n---------------"   songName   " has been added to the playlist!"   "---------------\n") ;

break;



case "3":

System.out.println("\n\t\tPRINTING PLAYIST\n------------------------------------");

play.printList();

break;

case "4":

if(currentSong == null){



if(play.getHead() != null){



currentSong = play.getHead();

System.out.println(currentSong.getName()   " "   currentSong.getArtist());



}else{



System.out.println("\nEmpty Playlist");

}



System.out.println();



}else{





System.out.println(currentSong.getName()   " "   currentSong.getArtist());

}



break;



case "6":



if(currentSong != null){





if(!play.comapreSongObj(play.getTail(), currentSong)){





currentSong = currentSong.getNext();

}else{





currentSong = play.getHead();

}



}

break;



case "7":



if(currentSong != null){





if(!play.comapreSongObj(play.getHead(), currentSong)){





currentSong = currentSong.getPrevious();

}else{





currentSong = play.getTail();

}



}

break;





default:

System.out.println("ERROR");

break;



}



menu();

//System.out.println();

System.out.print("Enter an option> ");

option = scanner.nextLine();



}



}



private static void menu(){



System.out.println("1 - Add a song to playlist\n2- Insert a New Song after the Song that is currently playing"  

"\n3 - Print Contents of the Playlist\n4 - Display the current song\n"  

"5 - Remove the current song\n6 - Skip to next song\n7 - Return to previous\n"  

"8 - Exit\n");

}

}

CodePudding user response：

Currently, your variable option is a String, meaning it can store letters and other characters (including numbers). The rest of your code also treats option as a String, so I'm assuming that's what you would like to go with.

In order to find the number inside a String, you can use the built-in Java method Integer.parseInt(yourString), which returns the number value inside the yourString variable. For example, if String s was "123", the method call Integer.parseInt(s) would return 123 (notice there's no quotation symbols, which means it isn't a String).

Here's how you could implement it in your code:

while (Integer.parseInt(option) < 1 || Integer.parseInt(option) > 8)
{
    System.out.print("Invalid input! Enter an option> ");

    option = scanner.nextLine();
}

Keep in mind that this will cause an error if the user enters a value that contains any non-numeric characters, such as "ab123".

Documentation for Integer.parseInt(yourString)

CodePudding user response：

Change var option to int and use nextInt() instead of nextLine() in your scans for that variable