effective java second edition

an implementation class for the target interface and to invoke a method of the appropriate interface in the implementation class. So as to achieve the purpose of adaptation.Example:Target rolepublic interface target{public void request ();}SOURCE rolepublic class adaptee{The original businesspublic void dosomething () {System.out.println ("a b C");}}Adapter rolepublic class Adapter extends Adaptee implements target{public void request () {Super.dosomething ();}}Object Adapter Mode:By wrapping a

OverviewIn distributed systems, there are scenarios that require the use of a globally unique ID, which can be used to prevent ID collisions using a 36-bit UUID, but the UUID has some drawbacks, first he is relatively long, and the UUID is generally unordered.There are times when we want to use a simple ID and want the ID to be generated in an orderly fashion.The snowflake of Twitter solved this demand, and initially Twitter migrated the storage system from MySQL to Cassandra, because Cassandra

"); +Numberc.remove ("E"); - } the if(Numberc.size () >=4numberc.contains ("F")) {//letter F for 5 excluding 0,2,4,6,8 after exclusiveBayiSb.append ("7");//7+8 = 15, take digit 5, is the smallest number theNumberc.remove ("F"); theNumberc.remove ("I"); -Numberc.remove ("V"); -Numberc.remove ("E"); the } the if(Numberc.size () >=5numberc.contains ("S")) {//letter F for 7 excluding 0,2,4,6,8 after exclusive theSb.append ("9");//9+8 = 17, take digit 7, is the smalles

Digital Signature Algorithm Java version or on the code bar public static final String sign_algorithms = "Sha1withrsa"; /** * RSA Signature * @param content pending Signature data * @param privatekey private key * @param input_charset encoded format * @return Signature value */Publi c static string sign (string content, String Privatekey, String input_charset) {try {byte[] de Code =base64.getdecoder (). Decode (Privatekey);

(sequence = = 0) {//Blocks to the next millisecond, obtaining a new timestamp timestamp =Tilnextmillis (Lasttimestamp); } }//Timestamp change, sequence reset in millisecondsElse{sequence = 0L; }//Time truncation of last build id Lasttimestamp =Timestamp//Shift and join or operate together to form a 64-bit IDReturn ((Timestamp-twepoch) // | (Datacenterid // | (Workerid // |Sequence }/*** block to the next millisecond until a new timestamp is obtained *@paramLasttimestamp time of last generation

1, in order to get two exactly the same array (1) loop traversal (2) The Arraycopy method of the System class.2. When the array is passed as a parameter of the method, the array is passed the reference, and the operations of the arrays affect the original arrays.3, this keyword (1) implicit parameter Reference (2) calling other constructor methods in the class4. Super keyword (1) Call parent class method (2) Call parent class constructor method5. The instanceof operator in

Reason:Default Web. XML Configurationall requests to the site go through the struts2 filter, which means that Ckfinder related requests are struts2 intercepted, resulting in requests for servlets that are not ckfinder configured. Workaround: Implement STRUTS2 filter, judge whether Ckfinderde request, if is release, otherwise the default struts2 way continue to go down. Some of the code is as follows: Import Org.apache.struts2.dispatcher.ng.filter.strutsprepareandexecutefilter;public class

firing frequency set, each step to a certain probability of firing bullets. The direction is automatically changed when the obstacle is encountered.10, Map EditorThe Map Editor can select the appropriate obstacle from the right and place it on the map, and select the shovel to clear. Click the Save button (actually this is not a button), then automatically save the map to the maps directory in the edit.tkm file, renaming the file can be used as a normal map use (such as 5.tkm to become the fift

, so there is a good benefit of generating the configuration file here is that my program does not need to write dead is in the program need to completely write the information about the database to enter, Here I just need to read the configuration file and inject it into the relevant method. As for the configuration file generator is to create a file, and then according to the corresponding configuration data written to the file, of course, this is an XML file, you can use dom4j and so on to sc

"); Db.setuser (DbUser); Db.setpassword (Dbpassword); Db.setname (DbName); } } returnDB; } } The configuration file generator is to write the information about the database to the configuration file for the system to connect to the database when read, so there is a good benefit of generating the configuration file here is that my program does not need to write dead is in the program need to completely write the informat

Introduction to Java from getting started to giving up: object-oriented concepts (Entry edition ), To know what object orientation is, you must first have an object · Okay, we are joking. We need to explain what object orientation is. Example: "Silly, what did you eat for breakfast today ?" Silly: "You can eat a lot of food. There are two slices of bread, a chicken pie, a few dishes and leaves, a little s

the traditional blocking IO, and if it does not block, then it is non-blocking IO. Received the operating system IO model, but also have to mention SELECT/POLL/EPOLL/IOCP, about the four understanding, not much to explain, I have not understood in place.Understandably, after Linux 2.6, the implementation of Java NIO is achieved through Epoll, which can be found through the source code of the JDK. AIO, which is implemented through IOCP on Windows, i

, then all the columns are finished, find a suitable, continue the third Queen, or the first column, the second column ... Until the 8th queen can be placed in a non-conflicting position, we find a correct solution. Then go back to the first queen to put the second column, back to continue the loop ...Okay, start on the code.Package huisu;/** * Created by Wolf on 2016/3/16. */public class Wolfqueen {/** * total number of Queens (at this time set to 8 queens in the 8x8 chessboard, you can modi

. Through the synchronous lock, it realizes the mutually exclusive access to "cruelty". for the production method produce () : When the warehouse is full, the producer thread waits and waits for the consumer to consume the product before the production line can be produced; After the producer thread has finished producing the product, all threads that synchronize the lock are awakened through Notifyall (), including " Consumer thread ", what we call" informing consumers of consumption ". for co

pair. Each time we compare, we copy the larger numbers from the back to the secondary array, making sure the numbers in the auxiliary array are ascending. After copying the larger number to the array, move the corresponding pointer forward one bit, then proceed to the next round of comparisons.After the detailed discussion above, we suspect summed up the process of statistical reverse order: First, the array is separated into sub-arrays, the number of reverse pairs in the sub-array is counted,

Java code to implement:/** * Enter an array of integers with positive and negative numbers in the array. One or more consecutive integers in an array make up a sub-array. * The maximum value of all sub-arrays is evaluated. Requires time complexity O (n) */package swordforoffer;/** * @author Jinshuangqi * * August 8, 2015 */public class E31greatestsumofsubarrays {Pub Lic Integer findgreatestsum (int[] arr) {if (arr.length ==0) return null; int greate

it.Analysis here, we can see that this is actually a very typical recursive thinking, so we write the following Java code:/** * Enter a string to print out all the permutations of the string. * For example, enter the string ABC, print out all the strings that can be arranged by the character A,b,c ABC,ACB,BAC,BCA,CAB,CBA */package swordforoffer;/** * @author Jinshuangqi * * August 7, 2015 */public class E28stringpermutation {public void swap (char[]

pointer is introduced, so we have to deal with the empty list separately. When the first linked list is an empty list, that is, its head node is a null pointer, then it is merged with the second linked list, and the process of the idler merge is the second linked list. Similarly, when the head node of the second linked list is a null pointer, we combine it with the first linked list to get the first linked list. If two linked lists are empty lists, the result of merging is to get an empty list.

numbers are pressed into the stack and the next number is not found, then the sequence cannot be a pop-up sequence.After the formation of clear ideas, we can have some code, the following is the implementation of Java code./** * Enter a sequence of two integers, the first sequence represents the stack's indentation order, and determine if the second sequence is the pop-up order for the stack. */package swordforoffer;import java.util.stack;/** * @auth

people met in the number 2, the benchmark number 3 and this 2 exchange, get a new array 2 1 0 3 7 9 3 5, the 3 as a split point, the entire array is divided into two parts, the left 2 1 0 and the right 7 9 3 Repeat the above steps to continue sortingThe Java code is as follows: Public classQuickSort { Public Static voidMain (string[] args) {//TODO auto-generated Method StubQuickSort QS=NewQuickSort (); int[] score = {10,9,8,7,6,5,4,3,2,1}; Qs.quickso