java certification study guide

Mulsocketclient {public static void main (string[] args) { Socket socket = NULL; InputStream is = null; OutputStream OS = null; Server-side IP address String serverip = "127.0.0.1"; Server port port number int port = 10000; Send content String data[] ={"First", "Second", "third"}; try {//Establish connection socket = new socket (serverip,port); Initialize stream OS =

server, put the thread into the list and let the server read 6.3 Briefly describe the shortcomings of this program and how to improve it.1. Messages received by the Client interface cannot be distinguished from who sent them.Improved method: When sending a message on the client and the server, it is flagged who sent it.2. Messages received by the server do not have a newline.Improved method: Displays a newline character on the server side of your message.3. Regardless of which end is first

in debugging: The main class could not be found or could not be loaded . Run successfully after removing the code from the package.Other (sentiment, thinking, etc., optional)This chapter of learning feeling although more knowledge points, relatively trivial, but the content is relatively simple, a lot of knowledge in learning C language has mastered, compared to the 12th chapter of abstract Things think the third chapter is easier to understand, but there are some small knowledge point understa

difference between the inheritance and interface, the book is very vivid examples, fish can swim, sharks are fish, clown fish is fish, so they are inheritance relationship, but people can swim, but people and fish there is no inheritance relationship, but the human and fish between the connection can be expressed by the interface. While this is understood, I cannot relate to how much of a difference these two definitions can have in a particular program. In short, to continue to learn or to fil

the class name of class-friendly member variables and class-friendly methods"; "" protected is "any class with a similar package, you can access class A class protected class variables and protected class method". "Friendly" is a bit bigger than protected permission. Problems in code debugging and the resolution process Issue 1: When it is necessary to compile three source files simultaneously, for example, Example4_8.java Circle.java C

the Java program design. objects, methods and other content is an essential part of the general Java Program Design content, and practice more dozen code, will gradually understand its routines, so as to understand its use.Learning progress Bar lines of code (new/cumulative) Blog Volume (Add/accumulate) Learning Time (new/cumulative) Important Growth

resources interrupt()The thread used to "wake up" The method was called sleep Thread synchronizationUsing the synchronized -Modified method, you follow the synchronization mechanism: When a thread a uses the Synchronized method, other threads must wait until thread A is finished using the method.Reconciling threads for synchronization wait()Method can be executed in the thread break, temporarily let the CPU use wait()Method must be notifyAll() awakened by method wait()

20165115 2017-2018-2 "Java Program design" Fourth week study summary textbook study summaryThe fifth chapter mainly focuses on the inheritance of subclasses, and introduces a series of methods and keywords on this basis. In the sixth chapter, the main content is the implementation of the interface.Code HostingLast week's summary of the wrong quizSupplement after

statistics.sh script)Learning progress Bar lines of code (new/cumulative) Blog Volume (Add/accumulate) Learning Time (new/cumulative) Important Growth Goal 5000 rows 30 Articles 400 hours First week 200/200 2/2 20/20 Second week 300/500 2/4 18/38 Third week 500/1000 3/7 22/60 Week Four 300/1300

and the resolution processA diagram error occurred while compiling code Example3_1The error indicates that you have written the name of a variable incorrectly, and that the change is successful.Code Hosting(run result of statistics.sh script)Last week's summary of the wrong quizIn this blog postLearning progress Bar lines of code (new/cumulative) Blog Volume (Add/accumulate) Learning Time (new/cumulative) Important Growth Goal 5000

Job 12-Stream vs. file 1. This week's study summary 1.1 summarizes multi-stream and file-related content in the way you like (mind map or other).In a package in Java, java.io many classes are defined to handle input and output in a variety of ways. All of the input stream classes are subclasses of abstract classes InputStream (byte input streams) or abstract classes Reader (character input streams), and all

-system under Windows, so only the command line does not have a visual interface, such as the need for the interface to call third-party software, the situation can be viewed using virtual machine. Issue 3: Compile XXX Complete, run is prompt: Exception in thread "main" java.lang.NoSuchMethodError:Student. Problem 3 Solution: Prompt class with the same name in the same package or project, change the class name, save to run normally. Code HostingLearning progress Bar

processSometimes we encounter when assigning a value that exceeds the defined range, for example, if we can easily exceed its upper limit of 127 when defined as byte, or if the precision is not correct, for example, the value we assign when using float in the definition exceeds its precision, thus making an errorProblems in code debugging and the resolution processYi Know i = 8, but what about J? 8? Or is it 8.8?ResultsSomething went wrong! Why, is it not mandatory to convert int i into a doubl

"\".Next, I want to print the string \hello world\, the following is the initial code:Failed again, please teach a bully to understand that the \ causes the compiler to ignore the original H and the last ", resulting in incomplete programs and syntax errors (unable to print the string), after debugging code as follows:Other (sentiment, thinking, etc., optional)Previously practiced in the C language course, I think this practice let me reap the most is to ignore the use of symbols and the use of

and the parent class by the keyword "extends", which means that the subclass expands and inherits the behavior of the parent class.4. Introduction of Class Diagrams: Class diagrams are tools for modeling to help us understand the relationship between the contents of a class, the parent subclass, and 161 pages of the textbook, as well as in the Bi Xiangdong Teacher's Java tutorial video.5.is-a: in inheritance, there is a is-a short interest between th

the parent class that defines a byte array of char arrays without final The default capacity is 16 characters String immutable One "" represents an array and then a new array consumes resources StringBuffer can be enlarged Default capacity by constructor call parent class constructor method pass 16 Create default array 2. Methods Append (type variable name) A) You can add any type of variableb) The return value is StringBufferStringBuffer buffer=new StringBuff

: In a database, a transaction is a unit of work consisting of one or more statements that update the database, and the transaction mechanism is that when a transaction is processed, the transaction can be committed to the database only if all the operations in the transaction are completed properly, and if an item is not completed, the work is undone.In the JDBC API, the system automatically commits transactions by default, so to make multiple statements into a transaction, you have to use the

data directly from the buffer operation on the line, and Scanner each time from the file operation, it is naturally more slow.2.2 Replace the PrintWriter with BufferedWriter to see if the speed of writing to the file has improved. Record the elapsed time of both. Try to analyze the reason.A: There will be ascension, it should be related to its buffer zone.Reference: Subject specific requirements see flow and Document Experiment Task Book-topic 1-2.2 to 2.3 Reference code: BUFFEREDREADERTEST.JAV

. Flow and Document Learning Guide (all the activities below are optional) Character stream with text file: Use PrintWriter (write), BufferedReader (Read)Writes the Student object (property: Int id, String name,int age,double grade) to the file Student.data, read from the file display.1.1 Generated three student objects, using PrintWriter's Println method to write Student.txt, one student per line, and each student's attribute separated by |.

difficult to imagine, as long as willing to drill, Ken next time, there will be some harvest!Learning progress Bar lines of code (new /Cumulative) Blog volume ( new/cumulative) Learning time (new/cumulative) Important growth Goal 5000 rows 30 Articles 400 hours First week 150/150 1/2 15/15 Second week 350/500 1/3 20/35 Third week