core java certification

This section begins the Java Multithreaded Programming learning, the basic concepts of the operating system, processes, threads are no longer mentioned, just understand Java for multithreaded programming support.First, inherit the thread class to create threadsThe Java language uses the thread class to represent threads, and classes that represent threads can imp

Thread pool is a key point to be mastered in multi-threaded learning.The cost of starting a new thread is higher because it involves interacting with the operating system. In this scenario, using the thread pool can improve performance, especially if you need to consider using a thread pool when you want to create a lot of short-lived threads in your program.I. How do I create a thread pool??Before Java5, the thread pool was developed manually, and from Java5 onwards,

that determines the elements participating in the comparison. for (int x = 0 ; x 1 ; X + +) {for (int y = × + 1 ; Y //to determine the previous one greater than the next, the position is replaced. if (Arr[x] > Arr[y]) {swap ( Arr, x, y); } } } } Bubble sort: ?? The No. 0 and the first comparison, if the No. 0 large and the first swap position, the first and second comparisons, the large back shift, the second and third comparisons,?????? And so on,

:" + gradefield.getint (student)); (Exception e) { e.printstacktrace (); }20}(2) Gets the public property defined in the current class and parent classTo get all the public properties defined in the current class and the parent class can call the GetFields function of the class object, and to get a specified public property, you can call the GetField method, as shown in the following code:private static void Showfields () { Student Student = new Student ("Bill"

. 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

Tag: Util indicates date () Date class specifies date standard int ringIn the Java core Technology volume, the first date class appears in a very high frequency, so we have a small integration of the date classThe date class has twoThe date class represents a specific time classThis constructor assigns a Date object and initializes it to represent the specified number of milliseconds because it is called th

Book: "Java Core Technology Vol. two advanced features 9"Time: 2017.9.4-17:131. FlowInput stream: An object from which a sequence of bytes can be read; abstract class (InputStream)Output stream: An object to which a sequence of bytes can be written; abstract class (OutputStream)Source of the stream: file, network connection, memory block.Byte-oriented, so it is inconvenient to process Unicode information (m

Well known in. NET, the key generated by the RSA class is in XML format, while other languages such as Java generally use the PKCS8 format key, JavaScript generally uses the PKCS1 format. We in the development process is likely to encounter the need to interface with other languages developed API, if we encounter RSA encryption and decryption, we must ensure that key is the same, in order to ensure the correct processing of data, we definitely need to

Java naming convention: The first letter lowercase, the first letter of the following word, the camel's name.Be aware of the label:typealiases> in the label properties> below.Four, mapper mapper :1) Resource way:1 "account.xml" />2) class mode:1 class="jd.com.proxydao.AccMapper" />Specification Requirements:1:mapper files and interfaces need to be under the same package.The name of the 2:mapper mapping file needs to be the same as the name of the int

API for the JDBC interface core@author IxenosJava.sql.* and Javax.sql.*|-Driver Interface: Represents the Java driver interface. All of the specific database vendors are going to implement this interface.|-Connect (URL, properties): A way to connect to a database. URL: The URL of the connection database URL syntax: JDBC Protocol: Database Sub-protocol://HOST: Port/Database User: Username fo

asvalues = Size.values();Returns an array containing the element size.small,size.medium,,size.extra_large.(4) The Ordinal method but the position of the enum constant in the enum declaration, where the position is counted from zero, for example Size.MEDIUM.ordinal () returns 1.7. Techniques for succession design(1) Placing public operations and domains in super-class(2) do not use protected domainsThis is because, first, the collection of subclasses is unrestricted, and any one can derive a sub

34 Return 35 instanceof 36 Static 37 Final 38 Super 39 This 40 Native 41 Strictfp 42 Synchronized 43 Volatile

, the algorithm converts each character using 1-4-byte encoding.Code point/code unit (JDK 5.0) A code point is a code value (Unicode encoding) that corresponds to a character in an encoded table.In Java, the char type describes a code unit with UTF-16 encoding.UTF-16 uses a different length of encoding to represent all Unicode code points . In the basic multilingual plane, each character is represented by 16 bits (often referred to as a unit of

A termJdk:java delelpment JitJre:java Runtime EnvironmentSecond, installation jdk1.8.0_25Setting environment variables (recommended to be installed directly under C-drive), using;C: \java\jre1.8.0_25\bin;Third, unzip the source file methodEnter C: \java\jre1.8.0_25Create SRC subdirectorymkdir SRCCdsrcUnzip the fileJar XVF. \src.zipI. Using command-line toolsJava Helloworld.java with

Java core programming-File operations, javafile 1. Overview Access to the File system is required for each language. java provides the File class to create, rename, delete, operate on the File list, and determine whether the File or directory exists. 2. Operations on files/Directories The operations include: 1: Create an object. 2: determine whether it is a direc

interrupted by Interruptedexcetpion"); Thread.CurrentThread (). interrupt (); //The interrupt state is cleared when the interruptedexception exception is generated, all the interrupts are reset or thrown out for subsequent code to detect if an interrupt has occurred } if(thread.currentthread (). isinterrupted ()) System. out. println ("Sub thread is interrupted"); ElseSystem. out. println ("Sub Natural Stop"); } }; Thread T=NewThrea

p264~p267:1. errors may occur in the program: User input error, device error, physical limit error, code error2. If some operations are not completed due to an error, the program should : return a security state and be able to allow the user to execute some other commands;or allow the user to save all operation results and terminate the program in a proper manner.3. The task of exception handling : Transfer control from the place where the error occurred to the error handler that can handle the

the action within the specified time, the thread stateAutomatically to operational (RUNNABLE).6) TERMINATED (thread end)When the thread executes at the end, it is in state, and this is when the thread's life cycle terminates.There are two cases of thread termination:One is normal end returnThe other is because the exception was previously terminated3. Key code to start a thread in JavaFirst, we have to know that the Runnable interfaceThe Runnable interface has a run () method that is used to st

In fact, with the previous article "the prelude to learning DES encryption algorithms" as the basis, it is easy to implement the DES algorithm.However, I found the source code from the Internet, written in Java, and written in C ++, but all the code seems to be the same. Why is it the same? At the beginning, I wrote a class and added all the methods to the class. I guess it would be hard to implement it once if it wasn't the author's skill. In additio

)throwsException {String identifier=Generatelicensekey (); SYSTEM.OUT.PRINTLN (identifier); }}Get JVM DataJVM data is an important set of parameters to monitor the application, the general local development can be connected to the corresponding process by jconsole to view the relevant metrics data, but the online environment is not suitable for viewing through the jconsole, so we now use Java code to obtain data, Then report it out and then show it