Java

A basic conceptA preliminary definition of a mutable class and an immutable class (Mutable and immutable Objects):Mutable class: When you get an instance reference to this class, you can change the contents of the instance.Immutable class: An

Puzzle the issue of inheritance. For instance methods: When naming the same, subclasses overwrite the methods of the parent class, and the access permission is at least as large as the parent class.

Puzzle One: Small problems with data operations1) to avoid using float and double type when the problem requires an exact answer, use the int long bigdecimal type. This is because not all decimals can be represented as exact representations of

This paper uses Java multithreading to realize the function of simulating the ticket selling of multiple stations.Keywords: Java multithreaded shared variable implementation runnable interface volatile thread synchronization.The code is as

Timer Introduction:(1) Basic method:Public Timer(): Creates a new timer. The associated thread is not running as a daemon.public void Schedule(timertask task, long delay, long period)Schedules the specified task to start repeating fixed deferred

String DateStr1 = "2013-10-01 10:10:10";String DateStr2 = "2013-10-02 11:11:11";DateFormat DateFormat = new SimpleDateFormat ("Yyyy-mm-dd HH:mm:ss");Date dateTime1 = Dateformat.parse (DATESTR1);Date dateTime2 = Dateformat.parse (DATESTR2);System.out.

HDU1002: Large number addition, PE n timesImportJava.util.Scanner;Importjava.math.*; Public classmain{ Public Static voidMain (string[] args) {Scanner cin=NewScanner (system.in); intT; T=Cin.nextint (); for(intz=1;z) { if(z!=1)

1 File objects Public classCreateFile { Public Static void Main(string[] args) {//Create a file path and name to manipulate //Where file.separator represents a system-related delimiter, under Linux:/windows: \ \ //path represents the

/**4-1 according to the fifth chapter of the textbook exercise 5-12 of the requirements of programming to achieve the assigned plural class complexnumber*/public class adu {public static void main  (String[] args) {}}class  complexnumber{private int 

/**4-3* Derive a subclass for the rectangle class defined in Experiment 3: a square class. If the square operation is also to find the circumference and area* What methods does this subclass need to define in addition to the methods inherited from

/*** 7-3* Programmed to receive a number of data entered by the user, sorting them in descending order.* Again accept a number entered by the user, using the method to find the data in the sequence,* If present, outputs the number of the data in the

Import java.awt.borderlayout;import java.awt.checkbox;import java.awt.checkboxgroup;import  java.awt.Container;import java.awt.Font;import java.awt.event.ActionEvent;import 

Import javax.swing.*;import java.awt.*;import java.awt.event.*;p ublic class Test extends JApplet {JPanel panel = new Jpane L (); int x1, y1, x2, y2; Graphics gra;public void init () {This.getcontentpane (). Add (panel), GRA = This.getgraphics ();p

Problem: When debugging Java source code, you can only see the source code, but cannot see the immediate value of the variable in the source codeCause: In order to save space, the JRE removes debug information from the class file when it is packaged.

In practical programming, to avoid the deadlock situation, but let you deliberately write a deadlock program is not too simple (there is a company will be such an interview), the following is a simple deadlock example.Synchronization of threads can

Remove some elements from list and setHow the error code is written:New Hashset(); Set.add ("aaaaaa"); Set.add ("bbbbbb"); Set.add ("CCCCCC"); Set.add ("dddddd"), Set.add ("eeeeee"), Set.add ("FFFFFF"), Set.add ("GGGGGG" ); for (String str:set) {

[Basic idea]Key: Find the right insertion position in the sequence that is already sorted in frontSteps:1. Starting with the first element, the element can be considered ordered.2. Take the next element and compare it in a sequential sequence of

Package hbaseexec2;/* * Create a students table and perform related operations */import Java.io.ioexception;import Java.util.arraylist;import Java.util.list;import Org.apache.hadoop.conf.configuration;import

Spring Source Code research-download-compile-import eclipse-verify, springeclipse- I. Environment Configuration Operating System: Unbutu14.04LTS JDK: 1.8.0 _ 40 Git: 1.9.1 Gradle: 2.2.1 2. Download the source code-compile-import eclipse-verify 1.

Server. xml and content. xml are automatically restored when Tomcat is configured. tomcat configures server. xml When processing Chinese garbled characters or configuring data sources, we need to modify the server. xml and content. xml files under