仅从主要方法使用扫描仪

Question

I have this class (with setters, getters and one method) that asks from a user a number indefinitely until he types -1. I've called the Scanner Method from both, the main method and the class itself, is there a way to call the Scanner method only once only from the main method and apply the input to the class every time it is needed? I really appreciate your help. If something is not clear, please contact me.

Here's the Class Code:

public class calculation {

int current = 0;
int maxNum = 0;
int minNum;
int counter=0;
float sum = 0;
float avg;

Scanner scan = new Scanner(System.in);


public void setMin(int min){
    this.minNum = min;
}

public int getMin(){
    return minNum;
}

public void setMax(int max){
    this.maxNum = max;
}

public void setSum(float sum){
    this.sum += sum;
}

public void minMax(int current){
    setMin(current);
    while(current!=-1){
        setSum(current);;
        if(current>getMin()){
            setMax(current);
        }else if(current<getMin()){
            setMin(current);;
        }

        current = scan.nextInt();

        counter++;
    }

    System.out.println("The smallest number you entered was: \n" + minNum);
    System.out.println("The biggest number you entered was: \n" + maxNum);
    System.out.println("The sum of all those numbers is: \n" + sum);
    System.out.println("The avarege number is: \n" + (sum/counter));

}

}

And here's the main method code:

public class minusOne {

public static void main(String[] args) {

    Scanner scan = new Scanner(System.in);

    calculation cal1 = new calculation();

    System.out.println("Type numbers at will, when finish, type -1 and press enter");
    cal1.minMax(scan.nextInt());

    scan.close();

}

}

Answer 1

From what I understand, you don't want to have two call to new Scanner(System.in);

To avoid this, you can simply, in your class calculation, write : Scanner scan;

And add a constructor :

public calculation(Scanner sc){
    scan = sc;
}

Of course, in the main method you should write : new calculation(scan)

I hope I answered your question

Note: in Java your classes name should start with uppercase letter, it should be Calculation

Answer 2

You have some alternatives for this, you can have your Calculator class with a constructor that takes a Scanner as a parameter and then store it in a field, or you cand have a public field in the Calculator class and in your main when you get the scanner just affect this field (but it should be private, you can change it via getters and setters methods).

 /* This is the first option*/
public class Calculation {

    int current = 0;
    int maxNum = 0;
    int minNum;
    int counter=0;
    float sum = 0;
    float avg;

private Scanner scan;

public Calculation(Scanner scan){
     this.scan = scan;
}
public int setCurrent(int current){
   this.current = current;
   return current;
}

public void setMin(int min){
    this.minNum = min;
}

public int getMin(){
    return minNum;
}

public void setMax(int max){
     this.maxNum = max;
}

public void setSum(float sum){
     this.sum += sum;
}

public void minMax(int current){
    setMin(current);
    while(current!=-1){
        setSum(current);;
        if(current>getMin()){
            setMax(current);
        }else if(current<getMin()){
            setMin(current);;
        }

    current = setCurrent(current);;

    counter++;
    }
    System.out.println("The smallest number you entered was: \n" + minNum);
    System.out.println("The biggest number you entered was: \n" + maxNum);
    System.out.println("The sum of all those numbers is: \n" + sum);
    System.out.println("The avarege number is: \n" + (sum/counter));

   }
}

/* Second option */
  public static void main(String[] args) {

    Scanner scan = new Scanner(System.in);


    calculation cal1 = new calculation();
    //if the field scan in Calculation is public
    cal1.scan = scan;
    //if it is private
    cal1.setScan(scan);
    System.out.println("Type numbers at will, when finish, type -1 and press    enter");
    cal1.minMax(scan.nextInt());

    scan.close();

}