Sorry, I don't work with Java since a long time. I have a class which sort int type, and I am trying to do this, but this does not compile:
MySort.sort(vectorOfInt, new Comparator() {
@Override
public int compare(Object o1, Object o2) {
return (int)o1 - (int)o2;
}
});
I would like to sort a vector of int using this method using the comparator to sort in ascending order.
public static void sort(T[] a, Comparator c) {
sort(a, 0, a.length, c);
}
The sample code is rather incomplete, but to begin with you cannot cast Object to int. Use
return (Integer) o1 - (Integer) o2;
instead.
First off, don't use Vector, or Hashtable for that matter, they both are considered deprecated for all practical purposes. Use List or Map implementations.
Use a List<Integer> instead, it is the modern and correct way to manipulate a list of Integers as objects.
final List<Integer> list = new ArrayList<Integer>();
... populate list ...
Collections.sort(list);
If you want to use a different Comparator then you can use:
Collections.sort(list, comparator);
Since Integer implements Comparable, this will by default sort the List<Integer> in ascending order. Integer for the details.
This is the correct, idiomatic way of sorting List and Collection classes in modern Java. Anything else shows you don't understand the language and what it provides.
Comparator it is already in Java 6. Comparator and 'Comparable` has been in the language since the beginning. If you want to sort Integer then it is already built in. I don't see anything ground breaking in your code example that is new or enhanced over what Integer already does.You can make a typed Comparator and you won't need to cast the arguments.
MySort.sort(vectorOfInt, new Comparator<Integer>() {
@Override
public int compare(Integer o1, Integer o2) {
return o1 - o2;
}
});
EDIT:
First off, please don't call an array a vector. Vector is a java class and people will assume that is what you are using when you name the variable vectorOfInt.
The compiler error you are getting is because the compiler doesn't know that your Comparator is operating on Integers. Since all it sees is an Object, it doesn't know that o1 is actually an Integer and can be unboxed to be an int. By specifying the comparator type, you provide more information and the conversion can be made implicitly.
T defined? It isn't a generic method, so it has to be set by the containing class. What is the class signature that contains sort()?