tricky java programming questions

incompatible, or if you want it to be incompatible, increment the version number manually.1->2->3 .....The second approach is to generate a hash value based on the structure of the class. Adding or subtracting a property, method, etc. can cause this value to change. I think this is the way to apply this scenario:Developers think that each time the class is modified to generate a new version number, do not want backward compatibility, the operation is to delete the original SERIALVESIONUID decla

What is a thread?A thread is the smallest unit that the operating system can perform operations on, which is included in the process and is the actual operating unit of the process.Programmers can use it for multiprocessor programming, and you can speed up operations-intensive tasks using multithreading.For example, if a thread takes 100 milliseconds to complete a task, it takes 10 milliseconds to complete the task with 10 threads.Java provides excell

inheritance information is called the parent class (the superclass, the base class), and the class that gets the inherited information is called the subclass (derived class). Inheritance allows for a certain degree of continuity in a changing software system, and inheritance is also an important means of encapsulating the variables in the program (if not understood, read Dr. Shanhong's "Java and Patterns" or "Design pattern Refinement" section on Bri

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

that you can also modify its value after you create the object. StringBuilder vs Stringbuffer:stringbuffer is synchronous, meaning it is thread-safe, but it will be slower than StringBuilder.8. How to construct a string quickly and repeatedly?In Python programming, you just have to multiply the string by a number to get it done, and in Java programming we can us

similarities and differences between synchronized and Java.util.concurrent.locks.Lock? Main similarities: Lock can complete all functions implemented by synchronizedMain differences: Lock has more precise line semantics and better performance than synchronized. The synchronized automatically releases the lock, and lock must require the programmer to release it manually, and must be released in the finally clause.21. What happens when I use synchronization on a static method? When a static metho

is then invoked according to the result of the processing to display the processing structure.The process of MVC: first the controller receives the user's request, invokes the corresponding model for business processing, and returns the data to the controller. The controller invokes the corresponding view to display the processing structure. and renders it to the user through a view. If you want to correspond to MVC in a project, the Jsp,controler in the view corresponding project corresponds t

program body) to all such interfaces. It can then invoke the interface's method on any object that implements the interface's class. Because of an abstract class, it allows you to use the interface name as the type of the reference variable. The usual dynamic binder will take effect. A reference can be converted to an interface type or converted from an interface type, and the instanceof operator can be used to determine whether the class of an object implements an interface. Copyright NOTICE:

with a short code. Convert multiple spaces to a space (5 points)String s = "s tr in G";S=s.replaceall ("+", "");7. Using the socket to write a program, the client sends a request to the server side (to send a string), the service side to send feedback information. (10 points)TCP protocolOnline examples many find themselves. Code too long8. Implement Oracle paging queries with SQL statements. (10 points)SELECT * FROM (select ROWNUM rn,t.* from TableName t where T.rn Select * from TableName where

main (string[] args) {Syst Em.out.println ("The square of the integer 7 is" + Square (7)); System.out.println ("\nthe square of double 7.5 is" + square (7.5));} public static int square (int x) {return x * x;} public static double square (double y) {return y * y;}}This code customizes two methods, showing the Java method overloads, one for the type int, one for the double type, and the int type automatically when the output is typed, the double type

-threaded access to shared resources, due to improper access, usually a thread locked a resource A, but also want to lock resource B, and in another thread, the lock resource B, but also to lock resource A to complete its own operations, two threads want the other's resources, Instead of releasing their own resources, two of threads are waiting for a situation that cannot be performed.Java Network Programming approximate process:UDP programmingSend si

) The Wait (), notify (), and Notifyall () methods are local methods and are final methods and cannot be overridden.2) The Wait () method that invokes an object can cause the current thread to block, and the current thread must have a monitor (that is, a lock) on this object3) Invoking an object's Notify () method wakes up a thread waiting for the object's monitor, and if more than one thread waits for the object's monitor, only one of the threads can be awakened;4) Call the Notifyall () method

1 , what are the aspects of object-oriented features ?　　The object-oriented programming language has 4 main features: encapsulation, inheritance, abstraction, polymorphism, etc.Details:http://www.cnblogs.com/guweiwei/p/6599289.html2 , access modifiers public,private,protected, and what is the difference between not writing (the default)? 　　Defaults to default when members of a class do not write access adornments. The default is equivalent to exposing

What is object-oriented programming?Process oriented: Follow the steps to solve the problemObject-oriented: the objects that make up the problem are decomposed into objects, the object as the basic unit of the program, and the program and data are encapsulated in order to improve the reusability, flexibility and expansibility of the program.Java three major features封装继承多态性Eight basic data types of Java8 Basic data types:byte、short、int、longfloat、double

API XXX", such as "Site:docs.oracle.com Java API JTextField"3. Summarize the working principle of Java event-driven, refer to and rewrite the textbook example 6-1 (p115-116), rewrite the applet as JFrame. 4. Why do I need to "knock" code? See Bowen to all BBS students: How to learn a good way. It's easier to go to the stupid method of Python. Item Two: Picture displayObjective: To understand the common way

1. JAVA programming ideology-getting started with objects Object entry If I have learned JAVA and have not read the book JAVA programming ideology, I am sorry to say that I have learned JAVA. In view of this, to is busy, secretly

following three questions:(1) Describe the event-driven mode of GUI in Java. event handling mode, various event listeners .... (2) Briefly describe the common ways in which strings are converted to numeric values and converted into strings in Java. The string type is converted to various numeric types: string s = "169"; byte B = byte.parsebyte (s); Short T = Sho

technique can reduce the amount of data transmission network, but also to fundamentally avoid the network transmission process of Chinese problems. If you must transmit Chinese characters in the network, such as the chat information in QQ, this requires that the character set code used by the client program and the character set code used by the server-side program be consistent, which is the most basic way to solve the problem. 13.5 Summary On the Java