treeset

the element and the Equals method.When the hashcode value of the element is the same, it continues to determine whether the equals of the element is true. If true, then the same element is considered not saved.If False, then store. If the hashcode value is different, then equals is not judged, thus increasing the speed of object comparisons.Linkedhashset : Orderly, HashSet sub-class . TreeSet : Sorts the specified order of the elements in the set col

Set Set 1.HashSetJust to repeat, no orderThe HashSet Add method calls Hashcode and equals, so objects stored in hashset need to override both methods. 2.TreeSetTo repeat, and can be sorted in some sort of orderThe TreeSet Add method converts the object to comparable and then invokes the CompareTo method, so the object stored in the TreeSet must implement comparable, overriding the CompareTo method 3.LinkedH

Essay Classification-Javajava Collection Framework Summary (5)--map Interface Usage Summary: Map is used to save the data (Key-vlaue) with the mapping relationship. The key of map does not allow repetition, that is, any two key of the same map object is always returned by the Equals method. The Falsemap contains a keyset () method that returns the set set of the map so that key is composed. The map collection is similar to the storage of set elements, such as HashSet, Linkedhashset, SortedSet (i

-safe:LinkedList source Display, performance is a doubly linked list:Code Show ArrayList and linkedlist Insert and query efficiency comparison:The output is:Is this a very surprising result?2. SetA, HashSetB, TreeSetSimple Analysis . Similarities and differences of HashSet and TreeSetWith:* All data is stored based on the Map .* All threads are out of sync* cannot store duplicate data (because data is stored via The MAP's key value, so duplicate data is not allowed)* can only be traversed by

outputting the list collection, the ToString () method for storing objects in the collection is invoked by default, so it is necessary to overwrite them in the class.If you do not overwrite the ToString () method, you must use the for (int i=0;i 3. The order of the list collection requires the help of the collections tool class, the Collections.sort (List,new Comparator ()) method. So you need to customize a comparer class to define your own comparison rules. 2, using set set to i

custom classes, we need to override the Equals and Hashcode methods in a custom class, mainly because there are no duplicate data elements allowed in the collection, and when the collection verifies the validity of the element (data elements are not repeatable), You need to invoke equals and hashcode validation. Please refer to the documentation for specific methods Implementing Class TreeSet TreeSet can

. If the newly added elements are not added to the collection, the hash value of the added element will be recalculated if not equal, and then addedTreeSet collection: A storage structure that uses a two-fork tree at the bottom, and HashSet is completely different from the mechanism of ensuring that the storage data is not duplicatedSpecific implementation:Method One: Using the default comparator comparable, this time need to store the object corresponding to the class implementation comparable

operation of the stack, this time inherits from the vector, provides the push,pop and Peek methods, peek is not ejected according to the data size to get the last element object.Second, set mainly has HashSet and TreeSet HashSet-the class is inherited from the set interface, relative to the list is to say that internal added elements can not be duplicated, of course, from the hash of the name is the hash algorithm to achieve the prevention of conflic

interface Comparator Comparator = new Comparator () {@Override public int Compare (object Object1, Object Object2) {if (Object1 instanceof Newbookbean Object2 instanceof Newbookbean) {Newbookbean Newbookbean = (Newbookbean) Object1; Newbookbean newBookBean1 = (Newbookbean) object2; The specific comparison method refers to the natural ordering of the CompareTo method, here only a chestnut return Newbookbean.getcount ()-Newbookbean1.getcount (

interface, which is ordered with a corner index and can be duplicated, and the LinkedList class is a linked list data structure, They determine whether the element is the same as the Equals method is used relative to ArrayList it is faster for adding or removing data to the collection data because only the end-to-end relationship adjustment is required, and for ArrayList, the index needs to be re-adjusted. So for the large data volume of the addition or deletion operation is linkedlist more eff

Tags: The most repeated characters in Java A string may contain ~ Multiple characters in Z, such as string = "aavlasdjflajeeeeewjjowejjojasjfesdvoeawje";. Find the letter with the most occurrences and the number of occurrences. If there are multiple duplicates, obtain them. 1. Introduce treeset: quickly find all the strings that appear through the set 2. Introduction of arraylist: In order to quickly sort, the sorted string is generated using strin

index list is a bidirectional list. It features efficient insertion and deletion, and inefficient random access. Therefore, do not use methods such as get (INT index) that contain index information. the problem is that sometimes we don't know whether a list is an arraylist or an external list. For this reason, JDK 1.4 introduces an interface randomaccess, which has no method, it is only used to mark whether a list supports efficient random access. Therefore, we can use the following code to det

) are required, use [java] Set s = Collections. synchronizedSet (new Hash Set (...); 6. You must use the remove Method of the iterator to delete data during the iteration. Otherwise, an exception occurs. 3. Define HashSet 1. It is a subclass of HashSet. 2. It maintains the order of elements in the form of a linked list, so it accesses the objects in the set in the order of adding. 3. The performance of sequential traversal is better than that of HashSet, but the performance of other operations i

Common methods for Set interfacesThe set set consists of the implementation classes of the set interface and the set interface. The set interface inherits the collection interface, so it contains all the methods of the collection interface. Common methods in the set interface are as follows:Because duplicate values are not allowed in the Set collection, you can use the AddAll () method in the Set collection to add the collection collection to the Set collection and remove the duplicate values.Im

principle of adding elements: When adding elements to HashSet, first HashSet calls the element's Hashcode method to get the hash code value of the element, A series of operations can then be used to calculate where the element is stored in the hash table. The following two scenarios exist in the stored procedure: 1: If the location of the element is not currently stored in any element, then the element can be stored directly Scenario 2: If the position of the element is currently prese

, thus increasing the speed of object comparisons.|–linkedhashset: Ordered, HashSet sub-class.|–treeset: The ordering of the specified order of elements in the set collection. Different steps. TreeSet the underlying data structure is a binary tree.the principle of a hash table:1, the key words in the object element (unique data in the object), the hash algorithm operation, and a specific algorithm value, th

Set: The elements are unordered (the order of storage and retrieval is not necessarily the same) and cannot be repeated.The set function is the same as the Collection function.------ | HashSet:How does one ensure the uniqueness of elements?Is done through two methods of elements, hashCode and equlas.If the hashCode value of the element is the same, the system checks whether equlas is true.If the hashcode value of an element is different, the equlas method is not judged.------ |

[Java class set] _ set interface notes Objectives of this chapter: Understanding the relationship between the set interface and the collection Interface Common subclasses of the Set interface: treeset and hashset Collection has now learned two types of interfaces: List and queue Set interface definition: The Set interface is also a sub-interface of the collection interface. However, unlike the collection or list interface, duplicate elemen

special methods can be used as a stack or queue to use;Features: Slow query speed, fast insertion and deletion, logical continuous, physical discontinuity;b) Set interface-can store unordered non-repeating elements, set set without subscript, elements can not be accessed by subscript;1, HashSet-the position that the element is deposited into the collection is determined by the hash code of the element; Hashcode (); The internal is also an array implementation;2,

set are unordered, in order of deposit and out of order. 3, the common set implementation class: HashSet, TreeSet. The hashset is not guaranteed to be orderly because of the structure of the hash table, and the TreeSet uses the natural sort.HashSet and TreeSet:1. HashSet we generally think of him as unordered (arranged in HashSet according to the hashcode of the