Java: Tuple, Greatest Common Divisor and least Common Multiples exercises

JavaApplication4.java

package javaapplication4;

import java.util.ArrayList;
import java.util.List;

/**
 *
 * @author grizmio
 */
public class JavaApplication4 {
    public static void main(String[] args) {
        System.out.println(leastCommonMultiple(5, 9));
        System.out.println(leastCommonMultiple(15, 14));
        System.out.println(leastCommonMultiple(2, 3));
        System.out.println(leastCommonMultiple(2, 200));
        
        System.out.println("--------");
        System.out.println(multiplesTuples(6));
        System.out.println(multiplesTuples(7));
        System.out.println(multiplesTuples(9));
        System.out.println("+++++++");
        System.out.println(multiples(6));
        System.out.println(multiples(7));
        System.out.println(multiples(9));
        System.out.println("Greatest common divisor: 3, 10: " + greatest_common_divisor(3, 10));
        System.out.println("Greatest common divisor: 4, 10: " + greatest_common_divisor(4, 10));
    }
    
    public static int greatest_common_divisor(int x, int y){
        int min = Math.min(x, y);
        int max = Math.max(x, y);
        
        List<Integer> max_mults = multiples(max);
        List<Integer> min_mults = multiples(min);
        for(int i: min_mults){
            System.out.println(i);
            if(max_mults.contains(i)){
                return i;
            }
        }
        return -1;
    }
    
    public static int leastCommonMultiple(int x, int y){
        int mi = Math.min(x, y);
        int ma = Math.max(x, y);
        int p = ma;
        for(;p%mi!=0;p+=ma){
        }
        return p;
    }
    
    public static List<Tuple<Integer, Integer> > multiplesTuples(int x){
        /* devuelve:
        (6) = [(1, 6), (2, 3), (3, 2), (6, 1)]
        (7) = [(1, 7), (7, 1)]
        (9) = [(1, 9), (3, 3), (9, 1)]
        */
        List<Tuple<Integer, Integer> > mults_a = new ArrayList<>();
        int last_greater = x;
        for(int i=1; i <= x ; i++){
            for(int d = 0 ; d <= last_greater ; d++){
                if( i * d == x){
                    mults_a.add(new Tuple<>(i, d));
                    last_greater = d;
                    break;
                }
            }
        }
        return mults_a;
    }
    
    public static List<Integer> multiples(int x){
        /* devuelve:
        (6) = [6, 3, 2, 1]
        (7) = [7, 1]
        (9) = [9, 3, 1]
        */
        List<Integer> mults_a = new ArrayList<>();
        int last_greater = x;
        for(int i=1; i <= x ; i++){
            for(int d = 0 ; d <= last_greater ; d++){
                if( i * d == x){
                    mults_a.add(d);
                    last_greater = d;
                    break;
                }
            }
        }
        return mults_a;
    }
}

class Tuple<X, Y>{
    private final X _x;
    private final Y _y;
    Tuple(X x, Y y){
        _x = x;
        _y = y;
    }
    
    X x(){
        return _x;
    }
    
    Y y(){
        return _y;
    }
    @Override
    public String toString(){
        return "(" + String.valueOf(_x) + ", " + String.valueOf(_y) + ")";
    }
}