core java questions

This series of Java-related written interview knowledge, several other articles are as follows: Java written examination questions finishing Eighth wave The seventh wave of the Java written test face The sixth wave of the Java written test face

In this article we are going to discuss the different types of face questions in a Java interview, which allow employers to test the candidate's Java and common object-oriented programming capabilities. The following sections are divided into two chapters, the first of which will discuss object-oriented programming and its features, common

The core concept of Java: interface (interface)Interfaces are at the same level as classes, and in fact, interfaces are a special kind of abstract class.Such as:Interface ia{}Public interface: Open InterfaceSimilar to a class, a file can have only one public interface and is the same as the file name.A public interface and a public class cannot be defined in a file at the same time.In an interface, all meth

Well known in. NET, the key generated by the RSA class is in XML format, while other languages such as Java generally use the PKCS8 format key, JavaScript generally uses the PKCS1 format. We in the development process is likely to encounter the need to interface with other languages developed API, if we encounter RSA encryption and decryption, we must ensure that key is the same, in order to ensure the correct processing of data, we definitely need to

) proxy.newproxyinstance ( fly.getclass (). getClassLoader (), new class[] {flyable.class}, new Objecthandler (fly)); } public static void Main (string[] args) { flyable fly = Flyfactory.getflayimpl (); Fly.addwing (null); System.out.println (Fly.fly ());} }Core Class Description:The JDK provides a class named Proxy.newproxyinstance (All-in-one). Where is the first parameter for the loader th

Exception handlingThe parent class in the exception structure Throwable class, its Exceptionlei class and the error class. What we can catch in the program is the subclass exception of exception.Error at System level: Error in Java Runtime Environment, we are not controllable.Exception is a program-level error: we can control it. 1) catch Exceptions in two ways: one is to add Try-catch to catch the exception, and the other is to declare the exceptio

the source file. If you do not place the package statement in the source file, the class in the source file is placed in a default packet.The compiler does not check the directory structure when compiling the source files. So as long as the source file is not dependent on other packages, the compilation error does not occur even if it is not in the declared package, but a run error occurs because the virtual machine cannot find the file.Package Scope:The parts marked as public can be used on an

Java core programming-byte stream of IO stream (2), javaio 1. byte stream A 1.1-byte stream is a stream that operates byte. Byte streams can operate on any data, such as media data, music, movies, and images. Of course, they can also operate on characters. Byte stream is based on byte stream, we know that a byte is 8 binary bits, a byte corresponds to an English character in the UTF-8, people found that usi

Running a Java program in a Web page is called an applet.ReflectionThis feature is used extensively in JavaBeans, which is the architecture of Java components.A program capable of analyzing classes is called reflection (reflective). The function of the reflection mechanism and its powerful, as can be seen below, the reflection mechanism can be used to: Ability to analyze classes in the run View obj

Found on the Internet can prevent the page scroll to the top or bottom of the time, the leakage of the small letter ugly Gray bottom, the following little part of the core code to share for everyone's reference! My core code: Prevent:function () {var startx = 0, starty = 0;//touchstart event function Touchsatrtfunc (evt) {try {//evt.preventdefaul T (); To prevent the browser zoom, scroll bar scrolling

In this article we are going to discuss the different types of face questions in a Java interview, which allow employers to test the candidate's Java and common object-oriented programming capabilities. The following sections are divided into two chapters, the first of which will discuss object-oriented programming and its features, common

have different implementationsMethod definitions in Java--------------------------1) A method allows the presence of multiple modifiers, with no order of precedence between multiple modifiers2) The return type is located after the modifier, and a method must have a return typeFor methods that do not return a value, the return type is void3) When there is a return value in the method, each branch in the method is required to have a return to ensure th

The ClassLoader is responsible for loading the. class file (possibly on disk, possibly on the network) into memory and generating the corresponding Java.lang.class object for it.Introduction of Class LoaderOnce a class is loaded by the ClassLoader to generate an java.lang.class instance in memory, the same class is no longer loaded.Unique identity of the class: In the Java language, a class is uniquely identified with its fully qualified name, but in

The working principle of hashmap is a common Java surface question in recent years. Almost every Java programmer knows HashMap, know where to use HashMap, know the difference between Hashtable and HashMap, then why this question is so special? It is because of the depth of the examination of the problem. This problem is often seen in senior or mid-level interviews, and may even require you to implement HASH

　 The Java Collection Framework is the most frequently asked question of Java interviewing, and it is necessary to understand the powerful features of Java technology to master the set framework. Here are some practical questions, often asked in the core

write operation, the operating system writes the stream passed by the write method and proactively notifies the application. It saves the cost of traversing the event notification queue in NIO. 4.java NiO Core: Channels,buffers,selectors Channel: All IO starts with a channel in NiO, and the channel is a bit like a stream. Data can be read from the channel to buffer, or it can be written from buffer to th

First, Anonymousinnerclass (anonymous inner Class) can extends (inherit) other classes, can implements (implement) interface (interface)?No, for the anonymous inner class, the words you see are in place:New This form of the new statement declares a novel anonymous class that expands on a given class or implements a given interface. He also creates a new instance of that class and returns it as a result of the statement.This is the essence of the anonymous class, which is itself an inheritance of

(); to } +}Exception in thread "main" Java.lang.RuntimeException:call aAt Com.eyu.onequeue.testexception.a (testexception.java:12)At Com.eyu.onequeue.TestException.demo (testexception.java:30)At Com.eyu.onequeue.TestException.main (testexception.java:5)caused By:java.lang.RuntimeException:call bAt com.eyu.onequeue.testexception.b (testexception.java:21)At Com.eyu.onequeue.testexception.a (testexception.java:10)... 2 morecaused By:java.lang.RuntimeException:call CAt COM.EYU.ONEQUEUE.TESTEXCE

main element between, child elements and child elements between the space also forget. If you only want to get child elements, you can do this:NodeList children = Root.getchildnodes ();for (int i=0;iNode child = Children.item (i);if (child instanceof Element) {Element childelement = (element) child;...}}This processing is still very troublesome, this is why the subsequent introduction of the DTD, the DTD can be used to standardize the content of XML, reduce some unnecessary validation process.L

Nio:new IOStarting with JDK1.4, the new IO, which can map a disk file into memory, we then read the data in memory.stored in the Java.nio packageJava NIO (new IO) is a new IO API introduced by the Java1.4 version, which can replace the standard Java IO API, which is now primarily used in servers, and is sufficient for us to write code that still uses traditional IO.Java NiO provides a different way of working with iOS than standard IO:Channels and buf