![]() still love to learn more, please advise if we can do it better. (Arrays.toString(elements)) //if null it will print null String stringArray=new String//i ended up using three loops and 2 extra variables ![]() ("Int Array Elements in reverse order:") The resulting Comparator applies the inverse of the natural ordering on a collection of objects. ![]() It's good sometimes we practice over an example, here is a full one:Īrrays.sort(intArray,Collections.reverseOrder()) Java Collections reverseOrder(comp) Method Collections.reverseOrder() The reverseOrder() method of Collections is used to derive the Comparator. Hoping persons can make use of this solution, and that your joy will even be comparable to mine. This link on how to implement comparable made things much easier for me. If implementation of a Comparable interface sounds daunting to you, I'd encourage you not to think that way, it actually isn't. The beauty (in my opinion) of this solution is that it can be used to sort user defined classes, and even more than that sort them by a specific attribute. To make use of this compareTo, we simply call Arrays.sort(mFreq) which will give you the sorted array freq mFreq. This gives you the following : public int compareTo(freq arg0) solution is that if you're making use of the Comparable interface you can switch the output values which you had specified in your compareTo(Object bCompared).įor Example : public int compareTo(freq arg0)Įlse if (this.magnitude. A code snippet which demonstrates this is as follows: List aList = new ArrayList() The Comparator interface is defined in the java.util package. Method 4 : Using StringBuilder.append () method. reverseOrder is a static method of the Comparator class. this methods return me a sort with ascending order. Here is a description according Java API: Returns a stream consisting of the elements of this stream, sorted according to the provided Comparator. That is, Collections. The simplest way, intuitively speaking, is Collections.reverse: Collections.reverse(myList) This method modifies the list in place. Method 3 : Using Collections.reverse () method. I have an ArrayList and want sort it in descending order. One can modify the list in place, create a copy in reverse order, or create a view in reversed order. Now, lets look at some of the methods using which we can reverse an array in Java: Method 1: Reverse Array in Place. Finally, the sorted ArrayList is printed. This effect is observable only in arrays with odd lengths. The unsorted ArrayList is printed and then the ArrayList elements are sorted in reverse order using Collections.sort() and Collections.reverseOrder(). Then ArrayList.add() is used to add the elements to the ArrayList. The sorted ArrayList in reverse order is: One argument for doing so is that the for loop is much cleaner than keeping track of indexes, or using an explicit iterator. Viewed 267k times 270 Im migrating a piece of code to make use of generics. ![]() Ask Question Asked 13 years, 6 months ago. The output of the above program is as follows: The unsorted ArrayList is: Iterating through a list in reverse order in java. ("The sorted ArrayList in reverse order is: " + aList) ("The unsorted ArrayList is: " + aList) Ĭollections.sort(aList, Collections.reverseOrder()) The ClassCastException is thrown by the Collections.sort() method if there are mutually incomparable elements in the list.Ī program that demonstrates this is given as follows: Example the list to be sorted and the Collections.reverseOrder() that reverses the order of an element collection using a Comparator. A list can be sorted in reverse order i.e.
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