equals() and hashCode()

public class Main {
    public static void main(String[] args) {

        ABC a = new ABC(123);
        ABC b = a;
        ABC c = new ABC(123);

        System.out.println("==:");
        System.out.println(a == b);
        System.out.println(a == c);

        System.out.println("\nequals():");
        System.out.println(a.equals(b));
        System.out.println(a.equals(c));

        System.out.println("\nhashCode():");
        System.out.println(a.hashCode());
        System.out.println(b.hashCode());
        System.out.println(c.hashCode());

    }
}

class ABC {
    public int i;

    public ABC(int i) {
        this.i = i;
    }
/*
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        ABC abc = (ABC) o;
        return i == abc.i;
    }

    public int hashCode() {
        return i;
    }
*/
}