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Java tutorial

Detailed explanation of the initialization sequence of elements in java classes

Copy the code. The code is as follows: public class Test4 {@Testpublic void test(){child child = new child();}}class parent{public static String paren

2024-11-20
Share what you should pay attention to when using Preferences to read and write the registry in JAVA

There is only one thing to pay attention to, that is, the key name or item name should not contain capital letters, otherwise the data cannot be read. The code is like this: Copy the code The code is as follows: Preferences preferences = Preferences.syste

2024-11-20
Reasons and solutions for why sudo command cannot be used when starting Java under Linux system

Operating system: centos 5.2 Scenario description: We have a WEB project. The customer requires that it be run as a normal user (such as chb). Then there is a button on the page. After clicking, you can shut down the computer. Implementation method: 1. JA

2024-11-20
In-depth analysis of java string class methods

Copy the code as follows: import java.nio.charset.Charset;import java.nio.charset.UnsupportedCharsetException;import java.util.Locale;imp

2024-11-20
In-depth analysis of locale in java

In projects, we often need to parse strings into Locales, but there is no easy-to-use class. Java itself provides 3 constructors, but in actual use, you need to parse them yourself, which is relatively cumbersome. Locale(langugae)locale(language,country)

2024-11-20
Velocity basic syntax introduction

1. Basic syntax 1. "#" is used to identify Velocity script statements, including #set, #if, #else, #end, #foreach, #end, #iinclude, #parse, #macro, etc.; such as: #if ($info.imgs)

2024-11-20
Comprehensive analysis of hashtable in java

Hashtables provide a useful way to optimize application performance. Hashtables are not a new concept in the computer field. They were designed to speed up computer processing, which is very slow by today's standards, while they allow you to query man

2024-11-20
Java custom error class sample code

In the program, an exception needs to be thrown, and then the error message is output in the user interface. One situation is to catch exceptions one by one when the last UI is displayed in the program, and then display the corresponding ErrorMessage. Som

2024-11-20
A brief analysis of the difference between ArrayList and Vector and the difference between HashMap and Hashtable in java

ArrayList and Vector mainly come from two aspects. 1. Synchronicity: Vector is thread-safe, which means it is synchronous, while ArrayList is thread-safe and not synchronous. 2. Data growth: when growth is needed ,Vector grows by one level by default, but

2024-11-20
A brief analysis of javax.servlet.Servlet, ServletContext interface

1. The ServletConfig interface is used to describe the relevant configuration information of the Servlet itself. The ServletContext interface is used to describe information related to the application (a Context configuration in server.xml, that is, a vir

2024-11-20
Analyze how to obtain beans configured in Spring in Java

1. What is Spring? Spring is a lightweight inversion of control (IoC) and aspect-oriented (AOP) container framework. 2. How to obtain Spring-configured beans in the program? Method 1: Save the ApplicationContext object code during initialization: Copy the

2024-11-20
java.imageIo implementation code for adding watermarks to images

Copy the code as follows: package com.blogs.image;import java.awt.AlphaComposite;import java.awt.Color;import java.awt.Font;import java.a

2024-11-20
Java image compression implementation ideas and code

Java image compression code copy code is as follows: package com.img; import java.awt.Image; import java.awt.image.BufferedImage; import java.io.File; i

2024-11-20
Parsing Hibernate + MySQL Chinese garbled problem

If it is a Windows system, then the system's default local character set is gb2312. In order for the data table to also use the gb2312 character set, we need to write the SQL statement to create the data table like this: Copy the code The code is as f

2024-11-20
A brief analysis of the usage skills of Split function in Java

For example, if you execute: "2|33|4".split("|"), the result will be: ""2334 It's strange, but you can still know the reason after reading the API description. The java.lang.string.split split method splits a Split the st

2024-11-20

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