How to Sort Collections in Java

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Sorted Set Ascending order By TreeMap Example To sort a set in Ascending order you can just add all the entries of the set into a java. So if you store the objects of string or wrapper classes, it will be Comparable.

The answer is you cannot sort an HashSet, why? Override public int compareTo Person p { return this. Somebody asked me recently, how do you sort an HashSet? Both of these options are covered in the following sections.

Java The SortedSet Interface

A that further provides a total ordering on its elements. The elements are ordered using theiror by a typically provided at sorted set creation time. The set's iterator will traverse the set in ascending element order. Several additional operations are provided to take advantage of the ordering. This interface is the set analogue of. All elements inserted into a sorted set must implement the Comparable interface or be accepted by the specified comparator. Furthermore, all such elements must be mutually comparable: e1. Attempts to violate this restriction will cause the offending method or constructor invocation to throw a ClassCastException. Note that the ordering maintained by a sorted set whether or not an explicit comparator is provided must be consistent with equals if the sorted set is to correctly implement the Set interface. See the Comparable interface or Comparator interface for a precise definition of consistent with equals. This is so because the Set interface is defined in terms of the equals operation, but a sorted set performs all element comparisons using its compareTo or compare method, so two elements that are deemed equal by this method are, from the standpoint of the sorted set, equal. The behavior of a sorted set is well-defined even if its ordering is inconsistent with equals; it just fails to obey the general contract of the Set interface. There is no way to enforce this recommendation, as interfaces cannot contain constructors. Note: several methods return subsets with restricted ranges. Such ranges are half-open, that is, they include their low endpoint but not their high endpoint where applicable. If you need a closed range which includes both endpointsand the element type allows for calculation of the successor of a given value, merely request the subrange from lowEndpoint to successor highEndpoint. For example, suppose that s is a sorted set of strings. If fromElement and toElement are equal, the returned set is empty. The returned set is backed by this set, so changes in the returned set are reflected in this set, and vice-versa. The returned set supports all optional set operations that this set supports. The returned set will throw an IllegalArgumentException on an java sort a set to insert an element outside its range. Parameters: fromElement - low endpoint inclusive of the returned set toElement - high endpoint exclusive of the returned set Returns: a view of the portion of this set whose elements range from fromElement, inclusive, to toElement, exclusive Throws: - if fromElement and toElement cannot be compared to one another using this set's comparator or, if the set has no comparator, using java sort a set ordering. Implementations may, but are not required to, throw this exception if fromElement or toElement cannot be compared to elements currently in the set. The returned set is backed by this set, so changes in the returned set are reflected in this set, and vice-versa. The returned set supports all optional set operations that this set supports. The returned set will throw an IllegalArgumentException on an attempt to insert an element outside java sort a set range. Parameters: toElement - high endpoint exclusive of the returned set Returns: a view of the portion of this set whose elements are strictly less than toElement Throws: - if toElement is not compatible with this set's comparator or, if the set has no comparator, if toElement does not implement. Implementations may, but are not required to, throw this exception if toElement cannot be compared to elements currently in the set. The returned set is backed by this set, so changes in the returned set are reflected in this set, and vice-versa. The returned set supports all optional set operations that this set supports. The returned set will throw an IllegalArgumentException on an attempt to insert an element outside its range. Parameters: fromElement - low endpoint inclusive of the returned set Returns: a view of the portion of this set whose elements are greater than or equal to fromElement Throws: - if fromElement is not compatible with this set's comparator or, if the set has no comparator, if fromElement does not implement. Implementations may, but are not required to, throw this exception if fromElement cannot be compared to elements currently in the set. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples. Scripting on this page tracks web page traffic, but does not change the java sort a set in any way.

If the natural ordering is used for this set, null is returned. If the Set is not typed, using , then you can even mix objects of different types classes in the same Set. How do we go ahead and compare the objects? In given examples, we will sort a collection of instances of Employee class. When you insert an element in than you lose the order guarantee. You can then access and iterate its elements without casting them. Since Set is an interface you need to instantiate a concrete implementation of the interface in order to use it. If you like GeeksforGeeks and would like to contribute, you can also write an article using or mail your article to contribute geeksforgeeks. Otherwise, if using a List, simply call Collections. Mail us on hr javatpoint.