head first core java

1. Threads and processesThere are many examples of processes and threads, because it is a learning note, that is, I feel very good understanding, is that we use the QQ every day, But we run the QQ.exe program, the process begins, we can open the Chat window at the same time, can be more than one video, and even the video side of the manual chat (maybe the sound is broken ...) Each of these tasks can be fully understood as a "thread" in the work, music, image emoticons, files and other functions

the methods in an interface (1) Declaring a class to implement a given interface requires the use of the keyword implements:class Employee implements Comparable(2) Then provide the CompareTo method for the employee class, assuming that you want to compare the employee's salarypublicintcompareTo(Object otherObject){ Employee other = (Employee) otherObject; return Double.compare(salary, other.salary);}Note that the CompareTo method is not declared as public in the interface declaration

p272~p2731. Exception handling except for catching exceptions: continue to pass the exception to the method caller. That is: Add the throws description symbol to the method header, replacing the try Catch statement.for the caller of the method : either handle the exception or continue to pass. (This is checked by the compiler)2, it is better to continue to pass the exception than to handle the exception forcibly .3 . The exception class range listed in the superclass method is not allowed to app

The inheritance according to our Chinese popular understanding is does not need to pay the effort, obtains other people's ability or the asset, for example inherits the father's property, inherits the father's expression ability, inherits the father's appearance and so on. Inheritance within a class can be understood without the need to re-develop the code, you can reuse the parent class method and domain.In the inheritance relationship, you can be divided into the parent class and the subclass,

runs out, the operating system deprives the thread of its running power and gives another thread a chance to run.3, blocked threads and waiting threadsWhen a thread is in a blocked or waiting state, it is temporarily inactive.To enter a condition that is blocked or waiting: When a thread attempts to acquire an internal object lock that is held by another thread, the thread goes into a blocking state. When all other threads release the lock, and the thread scheduler allows the thread to

=NewOutputStreamWriter (FileOutputStream); //building character output stream objectsBufferedWriter BufferedWriter =NewBufferedWriter (OutputStreamWriter); //Building Data Char[] chars =New Char[3]; chars[0] = ' a '; chars[1] = ' B '; chars[2] = ' Medium '; //Output DataBufferedwriter.write (chars); //Close the streamBufferedwriter.close (); Outputstreamwriter.close (); Fileoutputstream.close (); } Catch(FileNotFoundException e) {e.printstacktrace (); } Catch(IOExce

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

usually iterate over all the elements and process each element, using flow operations to improve efficiency in parallel processing, to follow "what to do" without limiting what to do, providing the opportunity for integrity optimization to improve efficiencyThe flow surface looks similar to the set, however:1. Streams do not store elements, they are stored in the underlying collection or generated on demand2. Stream operations do not change their source data3. If possible, the stream operation

　　　　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