Control of an integer value null-CodePudding

I'm taking some value with the scanner in class student : mat,name and surname. I want to finish the program when the insert of mat is == "" and not a code. For exemple when i insert mat: 8293 the program go on but when i will insert "" a blank value the program will finish. I think the mat value should be converted to an Integer but don't work the if block.

public static void inserimento() {
    Studente s=null;
    do{
        System.out.println("\nmatricola:");
        Scanner mat = new Scanner(System.in);
        int matricola = mat.nextInt();
        Integer i = Integer.valueOf(matricola);
        if(i.equals(null)){
          break;
        }       
      
        System.out.println("\ncognome:");
        Scanner cog = new Scanner(System.in);
        String cognome = cog.next();
      
        System.out.println("\nnome:");
        Scanner nom = new Scanner(System.in);
        String nome = nom.next();
        s = new Studente(matricola,cognome,nome);
    } while(true);
  
    System.out.println("fine inserimento");
}

CodePudding user response：

You can read the input like string and parse it to an Integer. This allow you to check if the input value is empty.

 public static void inserimento() {

    Studente s=null;
    do{
        System.out.println("\nmatricola:");
        Scanner mat = new Scanner(System.in);
        
        try {
            String matricola = mat.nextLine();
            if(matricola.equals("")){
                break;
            }   
            Integer i = Integer.valueOf(matricola);
            System.out.println("\ncognome:");
            Scanner cog = new Scanner(System.in);
            String cognome = cog.next();
            System.out.println("\nnome:");
            Scanner nom = new Scanner(System.in);
            String nome = nom.next();
            s = new Studente(matricola,cognome,nome);
        }
        catch(Exception e) {
            System.out.println("the input value must be Integer");
        }
       
    } while(true);
    System.out.println("fine inserimento");
}

CodePudding user response：

public static void inserimento() {
Studente s=null;
do{
    System.out.println("\nmatricola:");
    Scanner mat = new Scanner(System.in);
    String matricolaString = mat.nextLine();
    if(!matricolaString.equals(""))
    {
        int i  = Integer.parseInt(matricolaString);
    }
    else{
        break;
    }

    System.out.println("\ncognome:");
    Scanner cog = new Scanner(System.in);
    String cognome = cog.next();
  
    System.out.println("\nnome:");
    Scanner nom = new Scanner(System.in);
    String nome = nom.next();
    s = new Studente(matricola,cognome,nome);
} while(true);

System.out.println("fine inserimento");

}