treemap

Hashtable, Hashmap, and TreeMap are the most common map implementations, which are container types that store and manipulate data in the form of key-value pairs.Hashtable is a hash implementation provided by the Java class Library that is inherently synchronous, does not support null keys and null values, and is rarely recommended because of the performance overhead associated with synchronization.HashMap is the application of a more extensive hash ta

Turn from: http://blog.csdn.net/xin_jmail/article/details/24431835 Their understanding of Hashtable, HashMap, TreeMap, do not know whether there is a wrong place. HashTable: (1) is a two-dimensional array containing a one-way chain, in table array is entry (2) The value placed in cannot be null; (3) thread-safe, all methods are decorated with synchronized; HashMap: (1) The equivalent of Hashtable upgrade version; (2) can be put into null value; (3)

Package com.hephec.Map;Import Java.util.HashMap;Import java.util.Hashtable;Import Java.util.Iterator;Import Java.util.Map;Import Java.util.TreeMap;Class Hahsmaps{public static void Main (string[] args){MapMap.put ("A", "AAA");Map.put ("B", "BBB");Map.put ("C", "CCC");Map.put ("D", "ddd");Iteratorwhile (Iterator.hasnext ()) {Object Key=iterator.next ();System.out.println ("Map.get (Key) is:" +map.get (key));}Define Hashtable, which is used to testHashtableTab.put ("A", "AAA");Tab.put ("B", "BBB")

TreeSet and TreeMapRelationship between TreeSet and TreeMap: 1. TreeSet actually uses TreeMap to organize data, because an instance variable of the NavigableMap Public V put (K key, V value) {Entry The following figure shows a more intuitive display.First assignment: Store the value as the root node Final Entry // Use a custom Comparator to compare and traverse final Entry Sorting of Treeset an

Let's start by describing what the map is. In the array we index the contents of the array by subscript, whereas in map we index the object by object, and the object to be indexed is called key, and its corresponding object is called value. This is what we normally call key-value pairs.HashMap quickly find its content through hashcode, and all elements in TreeMap remain in a fixed order , and if you need to get an ordered result you should use

/* The TreeMap class implements the map interface by using a tree. TREEMAP provides an effective means of storing keyword/value pairs in sorted order, while allowing for fast retrieval. Unlike a hash map, a tree mapping guarantees that its elements are sorted in ascending order of keywords. */ Import java.util.*;Class treemapdemo{public static void Main (string[] args){Creat a tree mapTREEMAP TM = new

public class Testing {public static void main (string[] args) {hashmap　　TreeMap Sort By value

Package com.demo.base;Import Java.util.Comparator;Import Java.util.TreeMap;public class Test { public static void Main (string[] args) { Do not specify a sequencertreemapTreemap1.put ("2", "1");Treemap1.put ("B", "1");Treemap1.put ("1", "1");Treemap1.put ("A", "1");System.out.println ("treemap1=" +treemap1);Specifying the Sequencertreemap/** int Compare (object O1, Object O2) returns the integral type of a primitive type,* Returns a negative number indicating: O1 is less than O2,* Returns

PackageTest.tool.gui.common; ImportJava.util.Comparator; ImportJava.util.TreeMap; Public classTest { Public Static voidMain (string[] args) {//do not specify a sequencertreemapNewTreemap(); Treemap1.put ("2", "1"); Treemap1.put ("B", "1"); Treemap1.put ("1", "1"); Treemap1.put ("A", "1"); System.out.println ("Treemap1=" +treeMap1); //specifying the SequencertreemapNewTreemapNewComparator(){ /** int Compare (object O1, Object O2) returns an integer of the base type, * Returns a ne

intCompare (Student O1, Student O2) {inttemp =o1.getname (). CompareTo (O2.getname ()); returnTemp==0?O1.compareto (O2): temp; } }); Classtreemap.put (NewStudent ("Xiao Ming", 15), "Shanghai"); Classtreemap.put (NewStudent ("Xiao Li", 15), "Shenyang"); Classtreemap.put (NewStudent ("Xiao Xu", 13), "Wuhan"); Classtreemap.put (NewStudent ("Xiao Ming", 15), "Shanghai");//keys to treat as duplicatesClasstreemap.put (NewStudent ("Every Day", 14), "Wuhan"); Classtreemap.put (NewStudent

(key));//hm.get (key) Gets the value based on the key the } *}HashmapNewHashmap(); HashMapNewHashmap();Hm88.put (...) ... HashMapNewHashmap(); Hm.put (Hm88,Methyl); Hm.put (Hm99,Ethyl); //traversing a double-column collection for(Hashmap//Hm.keyset () represents a collection of keys in a double-column collectionString value = Hm.get (h);//Get (h) Gets the value object based on the key object//double-column collection object that iterates through a key for(Student Key

HashMap values:import java.util.hashmap;import java.util.map;import java.util.map.entry;import java.util.Set;/** *MAP Traversal * set*/ Public classTESTHASHMAP2 { Public Static voidMain (string[] args) {MapNewHashmap(); //add elements to the container: store them as key-value pairs.Map.put ("Jack","Jackie Chan"); Map.put ("Jay","Jay Chou"); Map.put ("Eason","Eason Chan");//adding elementsMap.put ("Jack","Jack");//if the key repeats, the overwrite will occurSystem. out. println (map); //Method 1

Map set HashMap TreeMap Output Method "Respect the original, reprint please indicate the source" http://blog.csdn.net/guyuealian/article/details/51934301how the collection is exported:The contents of a Collection, set collection can be converted to an object array output by the ToArray () method, and the list can be output using the Get method. There are four ways to output a collection class:(1) Iterator: Iterative output, the standard output form of

TreeMap, similar to TreeSet, allows you to sort the elements in the collection while preserving the uniqueness of the elements.It should be noted that comparable (implement interface, remember to overwrite Comparato method), comparator use.1 ImportJava.util.Iterator;2 ImportJava.util.TreeMap;3 4 Importcn.itcast.p2.bean.Student;5 ImportCn.itcast.p3.comparator.ComparatorByName;6 7 Public classTreemapdemo {8 9 Public Static voidMain (string[] args)

Use the java. util. TreeMap source code to understand the red and black trees,Preface This article combines the TreeMap source code of JDK1.6 to explore the mysteries of the Red-black tree. The red/black tree solves the imbalance problem of the Binary Search Tree. When a new node is inserted (or deleted), certain rules must be followed to keep the tree in balance. This rule is a red-black rule:1) each node

TreeMap, Comparable, and Comparator in JavaWe know that the storage location of HashMap is stored according to the hashCode of the key object, while that of TreeMap is stored according to the hashCode, it is stored according to the compareTo method of the implemented Comparable interface. As long as the returned result of compareTo is 0, the two objects are equal, so there will be no two objects, the put me

= Prime * result + (flag 1231:1237); Result= Prime * result + ((id = =NULL) ? 0: Id.hashcode ()); Result= Prime * result + ((name = =NULL) ? 0: Name.hashcode ()); Result= Prime * result + (int) (phonenumber ^ (PhoneNumber >>> 32)); returnresult; } @Override Public Booleanequals (Object obj) {if( This==obj)return true; if(obj = =NULL) return false; if(GetClass ()! =Obj.getclass ())return false; User Other=(User) obj; if(Flag! =Other.flag)return false; if(id = =NULL) { if(Oth

(); System.out.println (str+ "-+" +map.get (str)) ;//Remove content } }};Output Result:A, mldn-----www.zhinangtuan.net.cnWill find that the above to get the map key all get, take out, one by one output, found that the output of the second and third sequence and the input map is not the same, changed,This shows thattreemap the input content, sorted by key .Using TreeMap, you can easily complete the sorting operation.if the custom class wants

TreeMap Method Demo OperationImport Java.util.comparator;import java.util.hashmap;import Java.util.iterator;import java.util.TreeMap;public Class Treemapdemos {public static void main (string[] args) {treemapRun the programDark Horse Programmer--treemap Method demo operation

. substring (I). compareto (BSTR. substring (j ));If (k = 0) // last names match, Check entire nameReturn astr. compareto (BSTR );ElseReturn K;}} Public class treemapsort {Public static void main (string [] ARGs ){Treemap TM = new treemap (New tcomp ());TM. Put ("John Doe", new double (3434.34 ));TM. Put ("Tom Smith", new double (123.22 ));TM. Put ("Jane Baker", new double (1378.00 ));TM. Put ("Todd Hall",