java programmer certification

declares an instance variable, is not serialized when the object is serialized)Volatile (type modifier, used to decorate variables that are accessed and modified by different threads)ASSERT (assertion, which can be thought of as an advanced form of exception handling, captures the assumptions we make in our code)Note :main is not a keyword, but it is a name that is recognized by the virtual machine. Second, identifiersSome of the names that are customized in the program.Made up of 26 letters of

box. -Tf.addkeylistener (NewKeyadapter () { the @Override + Public voidkeypressed (KeyEvent e) { A if(E.iscontroldown () e.getkeycode () = =keyevent.vk_enter) { theSystem.out.println ("Enter run ..."); + } - } $ }); $ -F.addwindowlistener (NewWindowadapter () { - @Override the Public voidwindowclosing (windowevent e) { -System.exit (0);Wuyi } the }); - Wu //add a mouse listener on the b

argument.SummarizeBoth usages create the same number of object instances, except that the same number of local variables are repeatedly created within the loop, and the stack memory garbage collection frequency is higher, but the performance impact of stack memory is negligible for the performance impact of heap garbage collection and the business impact of the variable life cycle.Therefore, it is recommended to use a loop-defined variable, which restricts the life cycle of a variable to the sc

generic type Getgenerictype ()(4). Strong go to subclass Parameterizedtype (because the type does not have any corresponding methods)(5). Get generics True Type Getactualtypearguments ()11. Example:Package cn.itcast.day01;Import Java.lang.reflect.Field;Import Java.lang.reflect.ParameterizedType;Import Java.lang.reflect.Type;Import Java.util.HashMap;Import Java.util.Map;public class getgenerictypedemo{mappublic static void Main (string[] args) throws Exception {Class C = getgenerictypedemo.class

the critical section, causing the object to be damaged.Conditional object: The thread usually enters the critical section, but discovers that it can execute after a certain condition is met. To use a conditional object to manage threads that have acquired a lock but cannot do useful work. is called a condition variable.An object can have more than one related conditional object. Gets a conditional object using the Newcondition method.Lock interface: A synchronous code block or a synchronization

};for (int i=0; ipublic class Maopaosort{public static void Main (String args[]) {int [] a =new int{1,2,6,3,9,5,8,4,7};for (int i=0; iin fact, the two sorting methods are very similar, but in the order of the time when the comparison is not the same, this is the interview when the most frequently tested two sorts. 2. Find1. Two points Searchpublic class Halfselect{public static void Main (String args[]) {int [] a = {1,2,6,9,11,55,63,88};int min, max, mid;min = 0m Ax = Aa.length-1;mid = (min + ma

(double a,double b);//a B-square4, long round (double b); rounding5, double random (), greater than 0 is less than 1.0 of the stochastic number;1 PackageSystem;Do exercises2 /*given a decimal, keep the last n bits of the decimal point3 * 1, first multiplied by 10 of the N-square, and then rounded;4 * 2, divide this by 10 of the n-th square;5 */6 Public classXiaos {7 Public Static voidMain (string[] args) {8 //double D=baoniu (12.1564,2);9 //System.out.println (d);Ten // } One // A //

:++, + = First, the data type to the right of the operator is coerced into the same type as the left side of the operator, and the final result is consistent with the left side of the operator 2, should have the program analysis of the law (or the Law of the Debugging program), the problem decomposition, find its equivalent of the formula; the part to be debugged is isolated from the rest, and it is to reduce interference from other factors. 3, cultivate the habit of the principle of deep

follows:Importjava.lang.Runnable;ImportJava.lang.Thread;ImportJava.util.concurrent.locks.*;class Locks implements Runnable {PrivateLock lock =NewReentrantlock ();Private intindex =0; Public void Run() { while(true) {Lock.lock (); System.out.print (Index +" ");Try{Thread.Sleep ( -); }Catch(Exception e) {} index + +; Lock.unlock (); }}}class Demo { Public Static void Main(string[] args) {Locks Locks =NewLocks ();NewThread (Locks). Start ();NewThread (Locks). Start ();NewThread (

As a Java programmer who is often asked in an interview, let me summarize some of the questions that I often don't ask. The difference between 1.HashMap and Hashtable Often asked. Both are classes of the map interface, which enable you to map a unique key to a specific value. HashMap class is not sorted and can have a null key and multiple null values Hashtable, you cannot have null

Java programmer must read: basic articles Time: 2001/09/13 13:31 Author: ZSC Pacific Network College 　 2.6 What is an interface An interface is a contract that collects methods and constant forms. When a class executes an interface, it promises to declare that all methods are executed in that interface. An interface is a device or a system that is an unrelated entity for interaction. According to this def

is the method of reloading, and the other is the method of coverage.Polymorphic polymorphic and Object polymorphism (multiple forms of an object).The premise of polymorphism: Consider a subclass object as a parent object,Embodied in the code is animal a=new Bird (...);All polymorphism can be attributed to two theorems:1. You can look at the object as a parent class object, once you have done so, you can only invoke the original defined properties and methods in the parent class.That is, a metho

I have read this book before, and recently I think some of my views are quite correct. I have added some of my own summaries and sorted them out, hoping to provide guidance for future work and study. Three levels of programmers: Maybe Wang Guowei's eldest brother may look at how future generations develop his three realms of life in an interdisciplinary manner. There are many categories, so it must be well known. I am very pleased, haha! 1. programmer's First level: these buddies are generall

software.So, I think, although the pursuit of new technology is important, but if you want to improve, just continue to pursue new technology is not enough. New technologies can keep you in the short term, but will also keep you on the run. As a Java programmer, I think you probably don't know enough about the most important thing in developing Java applications

Describe:A buddy quit looking for a job, recently talked about the interview treatment requirements of a class of things, some feelings.In a company for a long time, the market for the development of the requirements are not so sensitive, and do not know what skills are required. A company's business is limited, stayed for 2 years, 3 years, 4 years later, the knowledge may be narrow;4, 5 years of programmers on the market average treatment is not clear, asked to say hello to friends to talk abou

of experts and lay a solid foundation, when will you be able to observe the industry and technology? You will be a beginner. Lz I just got started with php, but I am still learning it. It has been working and is surrounded by a lot of code all day. Without my own life, I lived a life of nine to twelve. A girl asked me two days ago, "Do you still have your own life?" health is very important. Indeed, half a year's programmer career, I have realized th

('. ' = current directory)Javac-d. Class name. java2. Generate a byte code with packet structure in the specified directoryjavac-d the specified directory (d:\test\) class name. java3. Run:You must run it on the specified directory at compile time above, Java package name. Class Name// no less write package nameIntroduction to the main packages in 12.jdk6java.lang-contains some of the core classes of the Java