core java for impatient

the element is placed inside the HASHMAP, first judge its hashcode, if hashcode not found, according to the Hashcode calculation index placed in the corresponding bucket, if hashcode the same, Then according to whether the key is equals as a second judgment, put in the corresponding linked list inside. /*** Adds The specified element to this set if it's not already present. * More formally, adds the specified element @parame element to is added to the this set *@return*/ Public BooleanAd

　　　　5 Btn.addactionlistener (Lsner); // as soon as a button is pressed, Lsner will be notified.View CodeThe listener class that implements the ActionListener interface must have a actionperformed method:1 classMyListener implements ActionListener2 3 {4 5 ... ..6 7 　　 Public voidActionperformed (ActionEventEvent)8 9{//as soon as the user taps the button, JButton creates a ActionEvent object that calls this method to pass the event object.Ten One 　　　　 //reaction to button click Goes here A -

{ //System.out.println ("thread [" + name + "] Get message:" + exchanger.exchange (name + "-msg")); //without setting the timeout time, the thread will always block waitingSYSTEM.OUT.PRINTLN ("thread [" + name + "] Get message:" + exchanger.exchange (name + "-msg", 5, Timeunit.seconds));//set the time-out for 5 secondsSYSTEM.OUT.PRINTLN ("thread [" + Name + "]over"); } Catch(interruptedexception e) {e.printstacktrace (); } Catch(TimeoutException e) {//TODO auto-generated Catch blockE

A basic data structureMust be included in the classMust have public static Main methodCase sensitiveIi. Types of dataFour types of integers:INT 4 byte short 2 byte Long8 byte byte1 byteTwo floating-point typesFloat 4 bytesDouleble 8 bytesChar Type, Boolean typeConstants use the final definition class constants using the static final definitionThird, Operation symbolsX!=0 1/x>x+y//If x=0, do not perform the calculation behind avoid x=0 1/x operationMathematical operation symbol MATH.PI, etc.Iv.

If multithreading is to concurrently modify a data structure, such as a hash table, it can easily break this data structure. A thread may want to start inserting a new element into the table. Assume that you are deprived of control during the process of adjusting the link relationship between buckets of a hash table. If another thread also starts traversing the same linked list, it may use invalid links and cause confusion, throw an exception, or fall into a dead loop.You can protect shared data

frame: jQuery1.9.CSS Framework: Bootstrap 4 MetronicClient authentication: Jqueryvalidation Plugin.Rich Text: CkecitorFile Management: CkfinderDynamic tab: JerichotabData table: Jqgriddialog box: JQuery jboxTree structure controls: JQuery ZtreeOther components: Bootstrap 4 metronic3. SupportServer middleware: Tomcat 6, 7, Jboss 7, WebLogic 10, WebSphere 8Database support: Currently only support MySQL database, but not limited to the database, the next version of the upgrade multi-data source sw

(list1.getclass () = = List2.getclass ());}Can try the results, I packed the tickets, the result is true3, attention.A generic parameter type can only be a reference type, not a basic data type, such as an int4, use of generics4.1 Generic classpublic class Generictest {public static void Main (string[] args) {GENERICCLASSG1 = new genericclassG1.setkey (1);System.out.println (G1.getkey ());}}Class genericclass{Private T key;public void Setkey (T key) {This.key = key;}Public T GetKey () {return t

frame: jQuery1.9.CSS Framework: Bootstrap 4 MetronicClient authentication: Jqueryvalidation Plugin.Rich Text: CkecitorFile Management: CkfinderDynamic tab: JerichotabData table: Jqgriddialog box: JQuery jboxTree structure controls: JQuery ZtreeOther components: Bootstrap 4 metronic3. SupportServer middleware: Tomcat 6, 7, Jboss 7, WebLogic 10, WebSphere 8Database support: Currently only support MySQL database, but not limited to the database, the next version of the upgrade multi-data source sw

The more efficient Java threads have always been, and then know the efficiency of execution and CPU core number, today we tried the multi-core CPU under multithreading calculation: This machine i5 four cores, opens 1, 4, 10, 20, 40, 100, 400 threads to do 100W times respectively, the result is as follows: All tasks completed, total time consuming: 38368ms,thr

byte[] B =New byte[3];//reading byte numbers, creating arraysRandomaccess.read (b, 1, 2);//read two bytes from pointer 1 write to array bString s =NewString (b);//Convert to StringSystem.out.println ("byte:" +s);//Output//Write FileFile file2 =NewFile ("C:\\img\\777.txt"); if(!File2.getparentfile (). exists ()) {File2.getparentfile (). Mkdirs (); } file2.createnewfile (); Randomaccessfile RandomAccess2=NewRandomaccessfile (File2, "RWD");//Accessi

. 245 page71 Video 8.6 Viewer mode for linkage Scenarios 8.4.3 page No. 25172 Video 8.7 Applying a dependency reversal principle can reduce the range of changes affected 8.5.1 No. 254 page73 Video 8.8 A single responsibility principle that can keep classes as stable as possible 8.5.2 No. 256 page74 Video 8.9 The Richter replacement principle to follow when inheriting 8.5.3 No. 257 page75 Video 8.10 Optimizing inherited usage scenarios by using the synthetic Multiplexing Principle page No. 261 of

Lambda An expressionform: parameter, arrow (-), expressionParameter type to write, if you can deduce it can not writeOnly one argument can omit parenthesesNo arguments to write empty brackets ()* If the branch returns a value, then all branches will return a value, otherwise it is illegalfunction interface: interface with only one abstract method (can be marked with @functionalinterface annotations)For example, you can do this in Javax.swing.Timer.　　　　　　Timer T = new timer (+, event-{...});The s

For this code, a lot of netizens are full of questions, first there are many, not careful, did not write the pair class, to compile.Certainly compiled, the pair class is on the first two pages of the other code.And here, the features of generics are written. By several constructors, and the change of parameters, the generic type is explained.Package pair1;public class pairPrivate T first;Private T second;Public Pair () {first = null;second = null;}Public Pair (t first, t second) {This.first = Fi

Why is the use of volatile lower than the cost of synchronization? The cost of synchronization is mainly determined by its coverage, and if you can reduce the coverage of synchronization, you can significantly improve program performance. And volatile's coverage is variable-level only. Therefore, its synchronization cost is very low. What is the volatile principle? Volatile's semantics, in fact, is to tell the processor, do not put me into working memory, please directly in main memory opera

schematic, the inside of the compiler is certainly not outer An implicit reference to an external class is set in the constructor. The compiler modifies all constructors for the inner class, adding a parameter that references the external class. Even if you do not define a constructor for an inner class, the compiler generates a default constructor for the inner class. such as:Publictimeprinter (talkingclock clock) {outer = clock;}When an inner class object is created in the Start method, th

1. ExceptionsThe user wants the program to take some sensible action in the event of an error. If some operations cannot be completed due to an error, the program should: return to a security state and be able to make some other commands, or allow the results of all operations to be saved and terminate the program in an appropriate manner.Exception handling tasks: Transfer control from where the error occurred to an error handler that can handle the situation.Exception Categories: Throwable:erro

The book is generally finished, but the seventh chapter is not in a hurry to end.But fortunately it is finished, barely count it.Recall this year, quite feeling, the heart has been seeking progress, but it is very difficult to act up.Think about it indeed ah, want to always progress must sacrifice their spare time, although not to exclude learning, but you have to admit that the feeling of paralysis is very good.Man, there's really nothing to stop, and once you get down, you're probably going to

JSTL Core Tag Library has a total of 13 tags, functionally divided into 4 categories: 1. Expression control Tags: out, set, remove, catch 2. Process Control Tag: If, choose, when, otherwise 3. Cyclic Tags: forEach, fortokens 4.URL operation tag: import, URL, redirect When using labels, be sure to include the following code in the header of the JSP file: These labels are described in the following sections: 1.