basic java interview questions and answers

? What is Futuretask? How to wake up a blocked thread? How do immutable objects help with multithreading? What does multi-threaded context switching mean? What thread scheduling algorithms are used in Java? What is the role of Thread.Sleep (0)? What is the Java memory model, which areas are thread-shared, and which are unshared What are optimistic and pessimistic locks? Why do I synchroniz

Java interview questions, java questions 1. storage structures used by stacks and queues Chain storage and sequential Storage 2. understanding of time complexity and space complexityTime Complexity: Number of statement executions in an algorithm, which is T (n). When n ch

Some questions that are frequently asked during interviews with Java programmers on the Internet, although a little old, are still worth reading. 1. Let's talk about the differences between final, finally, and finalize. Final? Modifier (keyword) If a class is declared as final, it means that it cannot generate a new subclass and cannot be inherited as a parent class. Therefore, a class cannot be declared bo

requirements graphically in various phases of software development; IBMRational Rose is one of the many UML modeling tools in the requirements phase, often used in drawing examples, class diagrams, sequential graphs. 15. Describe the tool class that you exported, and indicate the maximum amount of data POI (combining cell objects and background color applications) Finally here also found some of Baidu Library interview

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 (public) to other classes in the same packag

Interview Questions for Java engineers [social recruitment], java engineers Http://blog.csdn.net/jackfrued/article/details/44921941 1. What are the features of object orientation?2. What are the differences between access modifiers public, private, and protected?3. Is String the most

++;Parent.printvalue ();　　((child) parent). myvalue++;Parent.printvalue ();}}Operation Result:Summarize:When a subclass has the same method as the parent class, and a parent class variable refers to a subclass object, which method is called, determined by the object's own "true" type, that is, the object is a subtype, it calls the method of the subtype, it is the parent type, and it invokes the method of the parent type. This feature is actually a concrete representation of the object-oriented "

thread in the ready state by dispatching it to occupy the CPU and turn it into a running state. At this point, the system actually executes the thread's run () method.④ Blocking and waking threadsBlocking state (Blocked): A running thread enters a blocking state when it cannot continue running for some reason. These reasons include:(a) When a method of blocking type such as sleep () of a thread object is executed, the thread object is placed in a block set and waits for a timeout to automatical

single-threaded program can not produce OutOfMemoryError exception, using multithreading will also appear outofmemeoryerror, because the stack is thread-private, line multithreading also overflow method area3, JVM stack space allocation over the General Assembly caused by what problemshttp://blog.csdn.net/qq_30739519/article/details/510425844. How to detect dead loops and deadlocks in the JVMDeadlock: http://www.cnblogs.com/ilahsa/archive/2013/06/03/3115410.htmlDead Loop: http://blog.csdn.net/s

we don't want to repeat, we should use set. (2) Some collection classes allow the initial capacity to be specified, so if we can estimate the number of storage elements, we could use it to avoid a hash or resize. (3) Based on interface programming, rather than on implementation programming, it allows us to easily change implementations later. (4) Always use type-safe generics to avoid classcastexception at run time. (5) using the immutable class provided by JDK as the key of the map, you ca

digits to accurately represent (even need infinity), and the double type of the value of only 64bit, the back of the number of bits will definitely bring error, can not get "mathematically accurate" results.2. Questions about the number of bits and ranges represented by each data type in JavaA : The conversion of data types in Java, from high-precision like low-precision conversion will have a loss of p

= In.readline ();//read a line of content while(Line! =NULL ) { if(Character.isletter (line)) I++; Else if(Character.isdigit (line)) J++; ElseF++; Line=In.readline (); K++} in.close (); System.out.println ("Letter" +i+ "number" +j+ "Space" +j+ "number of lines" +k)}Catch(IOException iox) {System.out.println ("Problem reading" +fileName); } }}4, if there is a string "6sabcsfs33", with the most rapid way to remove the character "ab3", can not use the

overloading. 25th, can you inherit the string class? The string class is a final class and therefore cannot be inherited. 26th, when a thread enters an synchronized method of an object, can other threads enter other methods of this object? No, one synchronized method of an object can only be accessed by one thread. 27th, there is a return statement in try {}, so will the code in the finally {} after this try be executed, when it is executed, before or after it? Will execute, before return.

Question OneWrite a method that uses the above algorithm to generate a random integer of a specified number (for example, three). Answer: xn+1= (7^5*XN) mod (2^31-1)Program source code :import java.util.Random;import Java.util.Scanner; Publicclass Randomcount{ PublicStatic void Main (string[] args){Random rand=new random ();System. out. Print (" Please enter the number of random numbers you want to output:");Scanner in =new Scanner (System. in);int n,x;N=in.nextint ();X=rand.nextint (100); for

Java's current heat has declined, but there are still a lot of people who learn java. Java's post is also a lot of infiltration. So, those classic Java knowledge points, you can see the problem can say 123? Come and have a look.The difference between 1.JDK and JRE What is the difference between 2.final, finally, and finalize?3. The difference between threads and processesHow does the HashMap in 4.

I. Explanations of the following J2EE terms(1) JNDI: Java Naming Directory Interface, Java Naming directory service. the main function is to provide a directory system that allows applications from other places to leave their own indexes on it to quickly find and locate distributed applications.(2) JMS: Java Message Service,

The questions are as follows: Reference Answer: Import java.io.FileNotFoundException; Import java.io.IOException; Import java.util.ArrayList; Import Java.util.concurrent.ExecutorService; Import java.util.concurrent.Executors; /** * Created by YSC on 7/26/16. * * Public class Interview {private static void one () {String str1 = "Hello"; String str2 = "he" +new string ("Llo"); System.err.

1 . What are worker threads and SwingWorker and how do I use them? When a swing program needs to perform a long task, it is usually done using a worker thread. Each task executes in a worker thread, which is an instance of the Javax.swing.SwingWorker class. The SwingWorker class is an abstract class; You must define its subclasses to create a SwingWorker object, which is usually done using anonymous inner classes. SwingWorker provides some features of communication and control: [1]swingworker su

: The above can solve the POST request garbled problem. There are two garbled methods for GET request Chinese parameter:Modify the Tomcat profile add code to match the project code as follows: Another way to re-encode parameters: StringuserName =newString (Request.getparamter ("UserName"). GetBytes ("Iso8859-1"), "Utf-8") Iso8859-1 is the tomcat default encoding, and the Tomcat encoded content needs to be encoded by utf-8What is

J2ee /*** by Metaphy 2005-11-12* version:0.01* Note: The answer comes from metaphy past knowledge or network, metaphy can not guarantee its correctness or integrity, for reference only**/ First, the basic question and answer 　　1. Which of the following classes can be inherited? Java.lang.Thread (T)Java.lang.Number (T)Java.lang.Double (F)Java.lang.Math (F)Java.lang.Void (F)Java.lang.Class (F)Java.lang.ClassLoader (T) 　　2. The difference between abstrac