java j2ee interview questions

values that cannot be changed. The string provided by this StringBuffer class is modified. You can use StringBuffer when you know that character data is going to change. Typically, you can use Stringbuffers to dynamically construct character data.5. What are the similarities and differences between abnormal operation and general anomaly?An exception represents an unhealthy state that may occur during a program's run, and a run-time exception that represents an exception that may be encountered

are characterized by the inability to define variables, and all methods are abstract methods . abstract classes can have variables and do not enforce the need for abstract methods .Inheritance of class 16 and implementation of interfacesParsing: Class Inheriting the parent class implements the interface with the class, which is essentially the same. is to either extend or rewrite the parent class or interface as a template on this template. In practical programming, programmers often need to in

, and future to implement threads with return resultsThe Executorservice, callable, and future three interfaces are actually executor frameworks. The thread that returns the result is a new feature introduced in the JDK1.5, and with this feature it is no longer necessary to get the return value. And it can be flawed if it is achieved.A task that can return a value must implement the callable interface. Similarly, a task without a return value must implement the Runnable interface.After performin

Sword refers to Java Implementation of offer programming questions -- interview question 4 replaces spaces, and sword refers to offerImplement a function to replace spaces in a string with "% 20 ". For example, if the string is We Are Happy, the replaced string is We % 20Are % 20 Happy. 1 package Solution; 2 3/** 4 * offoffoffer

Java Exception Common interview question one, Java exception understandingExceptions are mainly handling errors that cannot be caught at compile time. The problem can continue to execute smoothly, without causing the program to terminate, to ensure the robustness of the program.Processing: When an abnormal state is generated, if the current context does not have

One: The difference between Eclipse and MyEclipseA: 1 common: Both are used to develop Java projects, and software usage is almost identical2 MyEclipse is a fee-free software, which can develop both Java and Web projects, Eclipse can only develop Java projects, if you want to develop a Web project, but also need to add additional Eclipse Web plug-in (of course, c

default branch, which must be the last branch of a switch statement. (3) default is executed when no case statement is equal to the value of the variable. The default branch does not require a break statement.Break is used to interrupt the loop statement, and continue is used to continue the loop. Breake break out of the loop body, continue continue the next loop, but the statement after continue is not running. Continue can only be used in loop statements, and break may be used in other branch

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 nul

The resume has some Ajax and struts issues.Growth strategy for database primary keyThe type of struts?Why use the difference between struts;session and cookies,Introduction to AjaxWhat are the built-in objects for 1.jsp?Four scopes for 2.jsp3. "". What is the difference between equals A and A.equals ("")?What is the difference between get and post for a 4.form form submission?What is the difference between 5.Cookie and session?How do 6.mysql and Oracle's primary keys come into being?7. Why use S

-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 side:1, create the Socket object constructor Da

position, filling the original AI (i), the AI value inserted into the space after the shift of J * * This implementation of a card from I, inserted into the exact position. Loop through the process sequentially, and each element of the loop is eventually inserted into the position it should be in, thus sorting is achieved. * [1, 2, 4, 5, 6, 7, 9, 3, 8] * [1, 2, 3, 4, 5, 6 , 7, 9, 8] * @param array * @param up */Public static void Insertsort (Int[] Array, Boolean up) {for

(); - } - - Public BooleanIsEmpty () {///Bottom call is LinkedList's IsEmpty () method to determine if the set internal data is empty - returnlink.isempty (); in } -}(2) test of Mystack:1 Packagecn.itcast_05;2 3 /*4 * Test of Mystack5 */6 Public classMystackdemo {7 Public Static voidMain (string[] args) {8 //To create a collection object9Mystack ms =NewMystack ();Ten One //adding elements AMs.add ("Hello"); -Ms.add ("World"); -Ms.add ("

multithreaded programs, multiple threads are executed concurrently to improve the efficiency of the program, and the CPU does not go idle because a thread needs to wait for resources. Multiple threads share heap memory, so creating multiple threads to perform some tasks is better than creating multiple processes. For example, Servlets is better than CGI because Servlets supports multithreading and CGI does not support it.How does the volatile keyword work in

rewrite the aof file, the performance impact of this persistence is minimal, but the aof file will continue to grow, aof file over the General Assembly to affect the recovery speed of master restart. Master should not do any persistent work, including memory snapshots and aof log files, in particular, do not enable memory snapshots to persist, if the data is more critical, a slave open aof backup data, the policy is synchronized once per second. Master calls bgrewriteaof rewrite aof file, a

wrapper type , which means that the wrapper type can be converted directly to the base data type , as shown in the following code:int m=100; Integer im=int N=im; The appeal code directly assigns m to the wrapper object IM, which is automatically boxed and then directly assigns the IM to the basic data type N, which is the automatic unpacking. Although the code on the surface is simple and convenient, however, in essence, the container still uses new to create the object, while unpacking is s

many occurrences in the array are greater than half @Test public void Test () {int[] num = {1,2,2,2,2,2,2,4,2,4,6,4,2,6,8,2,7,7}; SYSTEM.OUT.PRINTLN (Morethanhaft (num)); } public int morethanhaft (int[] num) {int result =-1; int times = 0, for (int i=0;iTopic Eight:Determines whether an array is the stacking order of another stack @Test public void Test () {int[] num = {1,2,3,4,5};//int[] num1={1,2,3,5,4}; int[] num2={2,1,5,3 , 4}; stackTopic Nine:Draw 5 cards from poker, 0

Today, I found the java interview programming questions in the Forum and thought about it. I found that I forgot my original programming basics. Question: How many equals 2x8 in the most efficient way? Along with the targeted thinking, I thought of 2x8. Later I thought that this efficiency was definitely not the best. think of the concept of a computer system,

1. String S1 = ' 123 ';String s2 = new string ();2. The difference between two ways of implementing multithreadingInheriting the thread and implementing the Runnable interface3. Single-column design mode What's the difference between lazy and a hungry man? * * *Lazy style Features: lazy loading. Delayed loading in multi-threaded security problems, through the addition of synchronization to solve, plus synchronization efficiency is low, with a double-judge method to solve the low efficiency. The

You can only manipulate a type to invert without a generic typeThe code is as follows: Packagecom.swift.fanxing;Importorg.junit.Test; Public classRenyireverse {@Test Public voidTest () {intarr[]=New int[] {1,10,6,9,2}; Reverse (arr); } Public voidReverseint[] arr) { for(inti=0;i) { inttemp=Arr[i]; Arr[i]=arr[arr.length-1-i]; Arr[arr.length-1-i]=temp; } for(intX:arr) {System.out.println (x); } }}Generic functionality can

take out 1 position: Product: 4 The consumer takes out from 0 position: Product: 2 producer put in 0 position: Product: 5 consumer removed from 0 Position: Product: 5 producer put in 0 position: Product: 6 consumer is removed from 0 position: Product: 6 producer put in 0 Location: Product: 7 producer puts 1 position: products £ º The producers are placed in the location of the product: 8 Position: Product Consumer removed from 1 position: Product: 9 consumer removed from 0 positions: Products: