collections singletonlist

I. Let's talk about it first.ArrayOfInsufficient(You can also saySetDifferences from arrays ): 1. arrays are fixed in size and cannot be scaled. Although the generic method system. array. Resize can reset the array size, this method re-creates an array with the new size and initializes it with elements of the old array. Then the previous array will be discarded! The set is variable-length. 2. the array must declare the element type. The element type of the Collection class is object. 3. the read

First, what is the moduleCommon scenario: A module is a file that contains Python definitions and declarations, and the file name is the suffix of the module name plus the. Py.In fact, the import loaded module is divided into four general categories:1 code written using Python (. py file)2 C or C + + extensions that have been compiled as shared libraries or DLLs3 packages for a set of modules4 built-in modules written and linked to the Python interpreter using CWhy use a module?If you quit the P

); intINDEX4 =collections.lastindexofsublist (List2, sublist); System.out.println (INDEX4); //replaces the specified element in the collection, or returns False if the element exists that returns true BooleanFlag = Collections.replaceall (List2, "Sunday", "TTTTTT"); SYSTEM.OUT.PRINTLN (flag); System.out.println (LIST2); //reverses the order of elements in the collectionCollections.reverse (LIST2); System.out.println (LIST2); //swap the position of the s

1. Use an extension method to use an enumeration value for the Description property value Public Static classenumextenstion{ Public Static stringGetdescriptionname ( ThisEnum Enumvalue) {Object[] attr =Enumvalue.gettype (). GetField (Enumvalue.tostring ()). GetCustomAttributes (typeof(DescriptionAttribute),false);if(attr. Length >0)return((DescriptionAttribute) attr[0]). Description;return "";}}2, gets the enumeration Description property value and the enumeration value for the relationship/// /

constructorArrayList list=new ArrayList ();for (int i=0;i② is constructed with a Icolliction objectArrayList list=new ArrayList (arryname)③ Initializes an internal array with the specified sizeArrayList list=new ArrayList (n);2, the addition of ArrayList elements①add method adds an element at the end②insert method Insert (index,value) index, value3. ArrayList element deletion①clear method to remove all elementsThe ②remove method removes the first object of a specified object, remove (OBJ)③remov

the form of Key=value in the Map collection.boolean equals(Object o)Determines whether the elements of the two set set are the sameThe lower level also overrides the Equals methodWhen we look at the HashMap collection, we do not find the Equals method, so we go to his parent class. V get(Object key)Gets the value of the corresponding element according to the key of the element in the Map collectionint hashcode()Returns the hash code value of the Map collectionboolean isEmpty()Checks out if ther

error occurs.>>> set1 = {"ALI", "RBQ", "TB"}>>> set1{‘RBQ‘, ‘ALI‘, ‘TB‘}>>> set1.remove("TB")>>> set1{‘RBQ‘, ‘ALI‘}>>> set1.remove("TTTT")Traceback (most recent call last): File "4. Member operators: in and not in>>> set2{5, 6, ‘RBQ‘, ‘Taobao‘, ‘1‘, ‘a‘, ‘s‘, ‘Google‘}>>> ‘RBQ‘ in set2True>>> 2 not in set2True>>> 6 not in set2False5. Set Operation: 并集；s1.union(s2) 或者 s1 | s2 交集：s1.intersection(s2) 或者 s1 | s2 差集：s1.difference(s2) 或者 s1 - s2 s2.denfference(s1) 或者 s2 - s1 对差等分

: Package test;import java.util.*;/*** @author Administrator**/ Public class Testhashset { Public Static void Main (String args[]) {hashsetNew hashsetlinkedlistNew linkedlistList.add ("List1");List.add ("List2");List.add ("List3");Hash.add ("hash Set1");Hash.add ("Hash Set2");Hash.add ("hash Set3");Hash.add ("hash Set4");Hash.add ("hash Set5");Hash.add ("hash Set6");Hash.addall (list);//The list added to the hash set is not present as a separate element, [List1, Hash Set6, LIST3, List2, hash set

Method One: Use the Arrays.aslist () methodString[] STRs = {"One", "one", "three"};listAttention:1) This method returns an array-based list view and does not create a list object, so the list cannot be added and deleted.Making modifications to the list Yes, it will also be modified to the array.2) The array is converted to a read-only list, using the Collections.unmodifiablelist () method to convert the array to list.3) Return to the list of deletions, using new ArrayList (Array.aslist (Array)).

design this program 'By using the nested implementations of map and map, the implementation code is as follows: Packagetest.day14;ImportJava.util.HashMap;ImportJava.util.Map;ImportJava.util.Scanner; Public classMapqiantaotest { Public Static voidMain (string[] args) {Scanner sc=NewScanner (system.in); HashMapNewHashmap(); Map.put (120, "36 gauge"); HashMapNewHashmap(); Map2.put (119, map); HashMapNewhashmapInteger, HashMap(); Map3.put (110, MAP2); while(true) {System.out.println ("Please enter

, but and HashTable not the same,TreeMap storage is closer to the same as a tree list, in the process of storing a Entry node will also be the Entry the left and right side of the node is saved with the parent node. , PS: If you need a more detailed understanding of The implementation of TREEMAP can query the red-black tree, because TreeMap is based on the red-black tree ( Red-black tree) is implemented. 4, WeakhashmapBasic functions and HashMap is the same, unlike HashMap , which is weakhashm

(NewString ("AA")); AColl.add (NewDate ()); theColl.add ("BB"); + - for(Object i:coll) { $ System.out.println (i); $ } - } - the //the wrong wording - @TestWuyi Public voidtest2 () { theCollection coll =NewArrayList (); -Coll.add (123); WuColl.add (NewString ("AA")); -Coll.add (NewDate ()); AboutColl.add ("BB"); $Coll.add (NewPerson ("MM", 23)); - -Iterator i =coll.iterator (); - A while((I.next ())! =NULL){ + //

on. If the tab cannot be displayed, make sure the. vimrc file is set with the set lcs=tab:>-command, and make sure that your file has a tab, and if Expendtab is turned on, tab will be expanded to a space.Vim TutorialsOn UNIX Systems$ vimtutorOn a Windows system: Help Tutor: syntax lists syntax items that have already been defined: syntax clear clears the defined grammar rules: syntax case match casing sensitive, int and int will be treated as different syntax elements: syntax case ignore upperc

What is an array?An array is an unordered sequence of elements, and all elements in an array have the same type.Declaring an array variable:Int[] A; the size of the array is not part of the Declaration;To create an instance of an array:A=new Int[3];Initialize the array variable:Int[] A=new int[2]{1,2};Int[] a={1,2};Time[] schedule={new time, New Time (5,30)};To create an implicitly-typed array:var name=new[]{new {name= "John", age=44},new {name= "Diana", age=45}};To iterate over an array:You can

static globally unique new Integer (0) value as no valueEnumsetInternally using a bit vector implementation, an abstract class that cannot be created directly from the new keyword, you must create a set of the specified enumeration type using another factory method method similar to noneof. The object that is actually created is a subclass of Enumset Regularenumset or Jumboenumset.The specific subclass type is determined based on the number of enumerated values of the enumerated type being pass

synchronous, that is, thread-safe , relatively low efficiency, suitable for use in multi-threaded environment, and HashMap is not synchronized, relatively high efficiency, Advocated for use in single-threaded environments. 3). The default initial capacity of the HashMap is 0.75, and theload factor isthe default initial capacity of the Hashtable is one and the load factor is 0.75.Properties class Inherits the Hashtable class, representing a persistent set of properties. Properties can be saved

() Determines whether a string ends a string with a string: The Split () string is converted to a list ("A delimiter needs to be defined in parentheses") join () convert list to string "format: x=" | ". Join (list) format string: Format () {} Replace with placeholder {index} Replace with the specified index {name} is replaced by the specified name for example: My name is {} ' age is {} '. Format (parameter 1. ..., parameter n) print ("My name is%s-age is%s"% ("Yyh", "+")) print ("My name is {na