How do I set a default and explicit value constructors?

See more:

Java

I'm starting a program and two of the requirements are these and I don't know where to start?

1. Default value constructor that sets the numerator to 1 and the denominator to 1
2. Explicit value constructor that sets the numerator and denominator to values specified by the user

What I have tried:

import java.util.*;
public class Rational
{
	int numerator = 1;
	int denominator = 1;
	Scanner kb = new Scanner(System.in);
	System.out.print("Please enter a numerator: ")
	numerator = kb.nextInt();
	System.out.print("Please enter a denominator: ")
	denominator = kb.nextInt();
}