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What is the most efficient way of sorting only a part of ArrayList? Say all elements from index 0 to 3 in an Arraylist which contains 10 elements.
Is there a library function available in Java?
Apart from Collections.sort(list) which sorts the entire List!
Writing a highly optimised custom sort function will take some work.
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In order to sort elements in an ArrayList in Java, we use the Collections. sort() method in Java. This method sorts the elements available in the particular list of the Collection class in ascending order. where list is an object on which sorting needs to be performed.
We can simply implement Comparator without affecting the original User-defined class. To sort an ArrayList using Comparator we need to override the compare() method provided by comparator interface. After rewriting the compare() method we need to call collections. sort() method like below.
Summary. Collections class sort() method is used to sort a list in Java. We can sort a list in natural ordering where the list elements must implement Comparable interface. We can also pass a Comparator implementation to define the sorting rules.
An element can be retrieved from the ArrayList in Java by using the java. util. ArrayList. get() method.
Collections.sort(list.subList(0,3)); Note: '3' here is excluded from sorting It is described in the documentation:
public List subList(int fromIndex, int toIndex)
Returns a view of the portion of this list between the specified fromIndex, inclusive, and toIndex, exclusive.
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use the subList [inherited from AbstractList] method in ArrayList. And then use Collections.sort() on that sub-list. That is if writing a highly optimised custom sort function is truly hard work.
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