android - reverse the order of an array
AndroidArraysReverseAndroid Problem Overview
I have an array of objects.
Is it possible to make a new array that is a copy of this array, but in reverse order? I was looking for something like this.
// my array
ArrayList<Element> mElements = new ArrayList<Element>();
// new array
ArrayList<Element> tempElements = mElements;
tempElements.reverse(); // something to reverse the order of the array
Android Solutions
Solution 1 - Android
You can do this in two steps:
ArrayList<Element> tempElements = new ArrayList<Element>(mElements);
Collections.reverse(tempElements);
Solution 2 - Android
Solution 3 - Android
Simple approach without implementing anything.
ArrayList<YourObject> oldlist = new ArrayList<YourObject>();
ArrayList<YourObject> newList = new ArrayList<YourObject>();
int size = oldlist.size()-1;
for(int i=size;i>=0;i--){
newList.add(oldlist.get(i));
}
Solution 4 - Android
For Android on Kotlin, this can be done with Anko's forEachReversedByIndex{}
lambda operation, like this:
val tempElements = ArrayList<Element>(mElements.size)
mElements.forEachReversedByIndex{tempElements.add(it)}
Solution 5 - Android
I reversed the Profile from ascending to descending order by
In kotlin
// A comparator to compare points of Profile
class ProfileComparator {
companion object : Comparator<Profile?> {
override fun compare(o1: Profile?, o2: Profile?): Int {
if (o1 == null || o2 == null) {
return 0;
}
return o2.points.compareTo(o1.points)
}
}
}
and then
var profilesList = profiles.sortedWith(ProfileComparator)