what is api in java

Click to enter _ more _java thousand ask1, meta-annotation is whatSee the comments here: what is the commentUnderstanding custom Annotations See here: How to customize annotationsMeta annotations are responsible for annotating other annotations. Java 5 defines 4 standard meta-annotations (meta-annotation): @Target, @Re

Power node Java Training What is a Web container? Provides an environment for the application components (Jsp,servlet) in which the Jsp,servlet directly and the environment variables in the container are connected to each other without concern for other system problems. There are mainly Web servers to implement. For example: Tomcat,weblogic,websphere and so on. T

Java garbage Collection Manual translation-What is garbage collectionAt first glance, garbage collection should do its name-find and throw away the rubbish. In fact, however, it does the opposite, garbage collection records all the objects that are still in use, and then marks the other as garbage. With this in mind, we started digging into the details of how mor

Q: What are processes and threads. A: The process is a collection of all threads, each of which is a path of execution in the process, and main is also a thread, and the primary thread. PS: Threads do not interfere with each other. Q: Why use multithreading. A: Improve the efficiency of the application, such as downl

assignment statement s= "" is a reference to a string type that points to another string (the value of the string is "", or an empty string).Common written Questions:New String ("ABC") has created several objects?Answer: one or two. Assuming that there is an "ABC" in the constant pool, then just create an object, assuming that there

Click to enter _ more _java thousand ask1. What is the difference between synchronous and asynchronous?In network programming, we often see synchronous, asynchronous, blocking, non-blocking, four calls and their combinations.Understanding blocking, non-blocking look here: [What is the difference between blocking and no

Nested class does not depend on an instance object of an external class,static Nested class can access the non- static The member variable . 5. When you access staticnestedclass, You can direct use static Nestedclass , without the need to add the name of the outer class, in staticnestedclass static member variable , you do not need to add the name of the external class. The inner class defined in the static method is also static Nestedclass

Java Comment Annotations x comment Note Difference x Comment Note Confusion Xjava comment Note Difference x note differs from comment xClick to enter _ more _java thousand ask1. What is the difference between annotations and annotations?See the comments here: what is the com

Heroes, the Java Thread.CurrentThread () what role ah. 397458726 | Browse 10,631 times 2009-09-16 13:39 2009-09-16 13:52 Best Answer Thread.CurrentThread () can get a reference to the current thread, typically by Thread.CurrentThread () when there is no thread object and need to obtain thread information.This answer is

the core classes required by the Socketchannel approach: ServersocketchannelAn alternative class of serversocket that supports blocking and non-blocking communication. SocketchannelAn alternative class of sockets that supports blocking and non-blocking communication. SelectorReceive Client Connection readiness events for Serversocketchannel monitoring and connect server read-ready and write-ready events for socketchannel monitoring. SelectionkeyRepresents the handle to the

Java program startup parameter-D is used to do what? To inquire about the official explanation:Set a System property value. If Value is a string of contains spaces, you must enclose the string in double quotes:java-dfoo= "some string" SomeClassThat is,-D

What is generic?First, we will write a simple generic class to illustrate:[Java]Public class Generics Private T o; // generic member variablePublic Generics (T o ){This. o = o;}Public T getObject (){Return o;}Public void setObject (T o ){This. o = o;}Public String getType (){Return o. getClass (). getName ();}}This generic class includes its own constructor, And

very prone to java.lang.ClassCastException anomalies(This example, I found in a blog, I can read the introduction of the generic example, but I executed the error, the wrong content is java:4: Error:cannot Find Symbol, may be my JDK version is wrong, I want to put the example of generics as soon as possible to finish, This mistake will be put here for the time b

general, because arrays are completely defined, type checking occurs both at the compiler and execution time, or the array itself is a holding object, and the generic container is simply checking for type safety in the compiler. But in the execution period is all object, is only half definition. Or, the generic contai

different manifestations. 】Polymorphism is a feature that cannot be applied independently, in fact. It is the upward styling and method of rewriting/override after a common effect. Some phenomena that appear when the program executes. In other words, the program code does not directly "write" polymorphic, just when the program executes, said: "Ah, I see polymorphic."So. From a programming skill or source p

numbers are converted to binary is also 1111 1111 1111 1111 1111 1111 1111 1111.So what does 1111 1111 1111 1111 1111 1111 1111 1111 mean?In fact:A memory is 32 consecutive 1, you put it according to an int to interpret is-1, according to unsigned int is 4294967295We can im

gives us a hidden danger. We should note that when object is null, the value of String.valueof (object) is the string "null", not null!!! remember to keep in mind when using the process. Imagine if we were to use if (string.valueof (object) ==null) {System.out.println ("the value passed in is null! ”);} Such a statement will likely be problematic. Think again, w

Note that the path to the result is not the same as a point, because he resolves the "." and ".." The situation.A third example: (using: "D:\\test\\absolutetest.txt" absolute path)File File = new file ("D:\\test\\absolutetest.txt"); System.out.println (File.getpath ()); System.out.println (File.getabsolutepath ()); System.out.println (File.getcanonicalpath ()); Results: d:\test\absolutetest.txtd:\test\absolutetest.txtd:\test\ AbsoluteTest.txtConclus

, testing, does not affect the normal use of online projects, such as testing completed, and then on the production environment. ）-----------------------------------------------------------------------General company how to build Java development, testing, production environmentThe most used code hosting is SVN, the local development with Windows+eclipse, the production environment with Linux (that

Click to enter _ more _java thousand ask1, Java.math package has what functionThe Java.math package provides a mathematical class in Java. Includes basic floating-point libraries, complex operations, and arbitrary-precision data operations. Main classes such as:?The classes in math are described below: arbitrary length shapingBigInteger, the arbitrary length of the non-variable shaping. Because the ba