Collections

[Abhishek Bose]

What is the difference between compareTo() and compare().Both of them compares two objects then what is the actual difference... example required..!!

[sri ramvaithiyanathan]

Click this Link for difference between compareto and compare.
For compareTo example click this

P.S:Give appropriate heading.

Regards,
Sriram

[Rajneesh K Rajput]

1. compareTo() takes just one argument.
If your class implements Comparable, i.e. you can only compare two of your same objects with one type of comparision logic.


2. Collects provides a mechanish for sorting by using Comparator interface.
This can be used in conjuction to create any no. of comparision logic, with any type of objects either in desc and asc order.

Advantages:
- You don't need to modify class code, which instance needs to be compared.
- You don't need to stick to one sorting logic and bind that with instances itself. (Covers in first step.)

Example:

List<String> myList = new ArrayList<String>();
		myList.add("A");
		myList.add("B");
		myList.add("C");
		
		Collections.sort(myList, new Comparator<String>() {
			@Override
			public int compare(String first, String second) {
				return second.compareTo(first);
			}
			});
		
		for(String out : myList)
			System.out.println(out);

This will give following output...
C
B
A

[Stephan van Hulst]

A Comparator provides a general ordering mechanism. Some advantages have already been given.

You should always consider a Comparable however, if your class has a natural ordering. If from your class, it seems obvious how instances should be ordered, make your class to implement Comparable.