entryset

10 Simple Java Performance optimizations:1. Using StringBuilder2. Avoid using regular expressionsWith regular expressions, you should at least cache the pattern to avoid compiling the pattern repeatedly.Static final Pattern Heavy_regex =Pattern.compile (((((*y) *z) * ");3. Do not use the iterator () method4. Do not call the high overhead method5. Using the original type and stackStored on the heapInteger i = 817598;Stored on the stackint i = 817598;6. Avoid recursion7. Use

over the elements of the map being passed in addition to the algorithm that the iteration put () runs to add each key-value pair to the map. It should be noted, however, that Putall () correctly adjusts the size of the map before it joins all elements, so if you do not adjust the size of the map yourself (which we will introduce), Putall () may be more efficient than expected. View MapThe elements in the iteration Map do not have a straightforward method. Suppose you want to query a map to see

　　One. HASHMAP staff = new HashMap (); Add keyword value pairs, write your own traversal Set entries = Staff.entryset (); Iterator iter = Entries.iterator (); while (Iter.hasnext ()) { Map.entry Entry = (map.entry) iter.next (); Object key = Entry.getkey (); Key words Object value = Entry.getvalue (); } 　　Two. Map map = new HashMap (); for (Iterator iter = Map.entryset (). iterator (); Iter.hasnext ();) { Map.entry Entry = (map.entry) iter.next (); Map.entry to remove key values si

(). toString (); String value=Map.get (key); System.out.println ("Key=" +key+ "value=" +value); } //Method 2: Use iterators, Fetch entryset ()Iterator iterator2=Map.entryset (). iterator (); while(Iterator2.hasnext ()) {Map.entry) Iterator2.next (); System.out.println (Entry.getkey ()+" "+Entry.getvalue ()); }(2) Enhance for loop, rewrite the above 2 methods // Method 1 for (String s:map.keyset ()) { System.out.prin

coercion of type conversions. It is often common in a collection frame. When the type of data being manipulated is undefined, the object class is earlier defined to extend, and now defines generics to extend.Generics can be defined on classes, methods, and interfaces, and for static methods in a class, the generics defined on the class cannot be accessed because the type of the generic is determined when the object is initialized, and the static method already exists at the time the class is cr

. ”Set EntrySet (): Returns the view set of the Map.entry object, which is the keyword/value pair in the image"Because the mappings are unique, you use set support." You can also remove elements from the view, and these elements will be removed from the source image, but you cannot add any elements. ”Map.entry interfaceThe map's EntrySet () method returns a collection of objects that implement the Map.entry

of the first occurrence of the specified element if the element does not exist return-1;So, by 1, you can tell if an element exists.int lastIndexOf (Object o): Reverse index Specifies the position of the element.List sublist (start,end): Gets the child list.4, modify:Object Set (index,element): Modifies elements of the specified index bit.5, get all the elements:Listiterator Listiterator (): A list collection-specific iterator.The list collection supports adding, deleting, changing, and checkin

over the elements of the map passed, in addition to the algorithm that the iteration put () does to add each key-value pair to the map. It should be noted, however, that Putall () can correctly resize the map before adding all the elements, so if you do not adjust the size of the map yourself (which we will briefly describe), Putall () may be more efficient than expected.View MapThe elements in the iteration Map do not have a straightforward method. If you are querying a map to see which elemen

iterations cannot use the Get method and can be traversed using iterators and enhanced for loops. Map In class, the main HashMap, it is a set of key-value pairs, key keys are not allowed to repeat, a key can only correspond to one value, but a value can correspond to more than one key. Used to pass data between different pages. For example, the use of Request.setattribute ()/getattribute () in JSP is implemented using this kind of collection. HashMap there is a method

Putall () can correctly resize the map before adding all the elements, so if you do not adjust the size of the map yourself (which we will briefly describe), Putall () may be more efficient than expected.View MapThe elements in the iteration Map do not have a straightforward method. If you are querying a map to see which elements satisfy a particular query, or if you want to iterate over all of its elements, regardless of the cause, you first need to get the view of the map. There are three pos

Map interface A map is an object that maps a key to a value. A map cannot contain duplicate keys: Each key can map a value at most. The map interface looks like this: public interface Map { // Basic Operations Object put(Object key, Object value); Object get(Object key); Object remove(Object key); boolean containsKey(Object key); boolean containsValue(Object value); int size(); boolean isEmpty(); // Bulk Operations void putAll(Map t); void clear(); // Collection Views public Set keySet(); pu

(Log.log_content_attribute_name); StringBuffer parameter=NewStringBuffer (); Maprequest. Getparametermap (); if(Parametermap! =NULL) { for(EntryEntry:parametermap. EntrySet ()) {String parametername=Entry.getkey (); if(!arrayutils.contains (Ignoreparameters, parametername)) {string[] parametervalues=Entry.getvalue (); if(ParameterValues! =NULL) {

Map interfaceInheritance diagram:Map Common methods Add, delete operations Object put(Object key, Object value) Object remove(Object key) void putAll(Map m) void clear Ways to manipulate meta views Set keySet() Collection values() Set entrySet() Element query operation Object get(Object key) boolean containsKey(Object key) boolean containsValue(Object value) int size() boolean is

Generics (generic) reverses all elements in the arrayMy Java Foundation has been not very good, recently took the time to strengthen their basic knowledge, basic skills, to go more practical.For the map collection, we have to use the enhanced for loop mechanism skillfully (for each), where EntrySet method is important.@Test Public voidTest1 () {MapString,Integer> Map = NewHashMapString,Integer>();Map.Put"AA",1);Map.Put"BB",2);SetEntryString,Integer>>

the rest of the elements returned: The enumeration set that initially contains the specified element is thrown: nullpointerexception-If any argument is null, or rest is nullenumset(iterator2.2. Noneof methodnoneof (classenumset Class); Enumset2.add (Weather.sunny); Enumset2.add (Weather.rainy); For (iterator 3. List Save enumeration type:New Arraylist(iterator4, Enummap class:enummapThe private MAP implementation used with the Enum type key. All keys in an enumeration map must come from a singl

contains both the key and value parts, while a enry key does not provide a modification method, and value allows for modification. It is necessary to note that if a mutable object is used as the key of the map, the behavior of the map is indeterminate (JDK1.6 document) If the change Equals () is different from the previous behavior.For abstract class Abstractmap, most of the implemented methods are based on the abstract method returned by the set of all Entry

", "User", "message", "gender");QueryBuilder QueryBuilder =Querybuilders.matchallquery (); Searchfunction (QueryBuilder); }2.6 Query Traversal Private voidsearchfunction (QueryBuilder querybuilder) {searchresponse response= Client.preparesearch ("Twitter"). Setsearchtype (Searchtype.dfs_query_then_fetch). Setscroll (NewTimeValue (60000) . Setquery (QueryBuilder). SetSize (100). Execute (). Actionget (); while(true) {Response=Client.preparesearchscroll (Response.getscrollid ()). Setsc

return all the keys of the collection, the other one returns a collection of all values, and then a return key and value combined into the EntrySet object collection, Map has a Get method, the parameter is key, The return value is a key corresponding to the value, this free play, nor the ability to test methods, these programming process will be prompted, combined with the differences between the three of them to say the use of the line.1 1. String s