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Stefan
Stefan

Reputation: 113

Reading a list of objects in Java

I'm a beginner in Java and wanted to know how can I read a list of objects in Java. I have a problem that asks to implement a list of rational numbers and print them (and some other methods)

    import java.util.Scanner;

public class Rational {
    private int a;
    private int b;

    public Rational (int a, int b){
        this.a = a;
        this.b = b;
    }

    @Override
    public String toString() {
        return a + "/" + b;
    }

    public static void main(String []args) throws Exception {
        // Take input from the user in the form of 2 numbers
        Scanner scanner = new Scanner(System.in);

    int n = scanner.nextInt();
    Rational array[] = new Rational[n];

    for(int i=0;i<n;i++) {

        int num = scanner.nextInt();
        int deno = scanner.nextInt();

    // Create a rational obj with 2 args
    Rational array[i] = new Rational(num, deno);
        }
    }
}

So I've tried to read an array of objects: ex: n=4 then first 2 3 second 5 4 .....

I'm getting an error saying Type mismatch: cannot convert from Rational to Rational[]

Upvotes: 0

Views: 979

Answers (2)

Parth Satra
Parth Satra

Reputation: 533

You can use something like

public class Rational {
    private int a;
    private int b;

    public Rational (int a, int b){
        this.a = a;
        this.b = b;
    }

    @Override
    public toString() {
        return a + "/" + b;
    }

    public static void main(String []args) throws Exception {
        // Take input from the user in the form of 2 numbers
        Scanner scanner = new Scanner(System.in);

        int num = scanner.nextInt();
        int deno = scanner.nextInt();

        // Create a rational obj with 2 args
        Rational x = new Rational(num, deno);
        System.out.println(x);
    }
}

Upvotes: 1

Boann
Boann

Reputation: 50041

Assuming you want to take input from the keyboard:

Scanner scanner = new Scanner(System.in);
List<Rational> rationals = new ArrayList<>(); // create a list
String line = scanner.nextLine(); // read list of numbers; e.g., "1/2, 3/4, 7/8"
for (String rational : line.split(",")) { // split string at each ","
    String[] parts = rational.split("/"); // split each of those at "/" character
    rationals.add(new Rational( // parse each half as int; create Rational; add to list
        Integer.parseInt(parts[0].trim()),
        Integer.parseInt(parts[1].trim())));
}

Upvotes: 1

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