Inapplicable method error regarding interfaces

I'm having an issue with one of my methods findLargest(Comparable[ ] arr) in class FindLargest that's meant to return the largest element in an array.

Apparently, in class Lab5Main this method works fine with fractions, but I get a compilation error with dates. In the system print out command, I'm getting this error:

> The method findLargest(Comparable[ ]) in the type FindLargest is not applicable for the arguments (MyDate[ ])

Here is the supposed program output:

The largest fraction is 9/4
The latest date is 18/8/2011

My codes are shown below:

public class Lab5Main {
public static void main(String[] args) {
// Fraction
Fraction fractions[] = new Fraction[3];
fractions[0] = new Fraction(1, 2);
fractions[1] = new Fraction(6, 11);
fractions[2] = new Fraction(9, 4);
System.out.println("The largest fraction is " + FindLargest.findLargest(fractions));
// MyDate
MyDate dates[] = new MyDate[3];
dates[0] = new MyDate(1898, 6, 9);
dates[1] = new MyDate(2003, 4, 1);
dates[2] = new MyDate(2011, 8, 18);
System.out.println("The latest date is " + FindLargest.findLargest(dates));
}
}

public class FindLargest {
public static <T extends Comparable<? super T>> T findLargest(T[] arr) {
if (arr.length == 0) {
return null;
}
T max = arr[0];
for (int i = 0; i < arr.length; i++) {
if (arr[i].compareTo(max) > 0) {
max = arr[i];
}
}
return max;
}

public class Fraction implements Comparable<Fraction> {	
private int num, denom;
public int gcd(int a, int b)  {  
if (a%b==0) {
return b;
}
return gcd(b, a%b);  
} 
public void reduce()  {  
int g = gcd(num, denom);  
num = num / g;  
denom = denom / g;  
}  
public Fraction(int n, int d) {
if (n==0) {
d=1;
}
if (d==0) {
n=1;
d=2;
}
if(d<0) {
n=-n;
d=-d;
}
num = n;
denom = d;
reduce();
}
public String toString() {
return num + "/" + denom;
}
@Override
public int compareTo(Fraction f) {
//		  Fraction f = (Fraction) obj;
if (Math.abs(value() - f.value()) < 0.00001) {
return 0;
}
if (value() > f.value()) {
return 1;
}
return -1;
}
public int compareTo(Object obj) {
Fraction f = (Fraction) obj;
if (Math.abs(value() - f.value()) < 0.00001) {
return 0;
}
if (value() > f.value()) {
return 1;
}
return -1;
}
}

public class MyDate implements Comparable<MyDate> {
private int year, month, day;
public MyDate(int z, int y, int x) {
if (z<1000 || z>3000) {
z = 2000;
}
if (y<1 || y>12) {
y = 1;
}
if (x<1 || x>31) {
x = 1;
}
day = x;
month = y;
year = z;
}
public String toString() {
return day + "/" + month + "/" + year;
}
@Override
public int compareTo (MyDate date){
//	  MyDate date = (MyDate) obj;
int diffYear = year - date.year;
if (diffYear < 0) {
return -1;
}
else if (diffYear > 0) {
return 1;
}
int diffMonth = month - date.month;
if (diffMonth < 0) {
return -1;
}
else if (diffMonth > 0) {
return 1;
}
int diffDay = day - date.day;
if (diffDay < 0) {
return -1;
}
else if (diffDay > 0) {
return 1;
}
return 0;
}
}

The issue is one of raw-types and generics. Comparable is a generic interface, but you are implementing it with a raw-type and you are using it with raw-types. You should fix that. Something like,

public static <T extends Comparable<? super T>> T findLargest(T[] arr) {
if (arr.length == 0) {
return null;
}
T max = arr[0];
for (int i = 0; i < arr.length; i++) {
if (arr[i].compareTo(max) > 0) {
max = arr[i];
}
}
return max;
}

will ensure that you call findLargest with a generic type T that can be compared with itself and all of its' superclasses. You should also change Fraction and MyDate. Something like,

public class Fraction implements Comparable<Fraction> { 
// ...
@Override
public int compareTo(Fraction f) {
if (Math.abs(value() - f.value()) < 0.00001) {
return 0;
}
if (value() > f.value()) {
return 1;
}
return -1;
}
}

And MyDate similarly. I would recommend you always use the @Override annotation when you intend to override a method.