Java

/*java uses transactions, first requiring the database to support transactions, such as the use of MySQL transaction functionality,MySQL is required to have a table type of innodb,*//*innodb, one of MySQL's database enginesCompared with the

Writing data to Excel that has data in the first place will not overwrite the original data, just append the data. public class Excel {    public Excel () {    }    public void Createworkbook (file file, double[] a) {        try {             if

Random entry: Automatic type conversion in an expressionThe char,short,byte is promoted to an int type and the result is int, but its original variable type does not change.So, byte B = 10; b = b*b; Errors will be encountered at compile time. But

I encountered this problem when the local deployment throws an exception Java.lang.OutOfMemoryError:GC overhead limit exceeded cause the service to not come, view the log found to load too much resources to memory, local performance is not good, GC

First, the class loading mechanism in Java has the following three properties:1. Overall responsibility System"Overall responsibility" means that when a classloader loads a class, the class that is dependent on and referenced by the class is also

1. java.lang.NullPointerExceptionThis exception is often encountered, the exception of the explanation is "the program encountered a null pointer", simply called an uninitialized object or a non-existent object, this error often occurs in the

Gradle is a generic build tool that allows you to build anything you want to accomplish with its build script, but only if you need to write the code for the build script first. And most of the projects, their build process is basically the same, we

These two days to learn the abnormal mechanism, which try...catch...finally personally think is an important link, linked to the previous study of the sentence, encountered a return and finally this fun problem, after testing, found that the logic

The Java collection classes have the following main types:1, list structure of the collection classArrayList class, LinkedList class, Vector class, Stack class;Importjava.util.ArrayList; Public classTest { Public Static voidMain (String args[])

In the fork/join skeleton, when submitting the task, there are two synchronous and asynchronous modes. It has been used for InvokeAll () the method is synchronous. Is anyThis method does not return until all of the tasks have been processed. There

In client/server communication mode, the server side needs to create a serversocket,serversocket that listens on a specific port to receive client connection requests.first, the construction serversocketThe ServerSocket method has the following

1. Traversal of the Map collection (key-value pairs object-find key and value)Map--Couples onIdeas:A: Get a collection of all marriage certificatesB: Walk through a collection of marriage certificates, get every marriage certificateC: Obtain husband

Bytearrayinputstream and Bytearrayoutputstream memory streams, operations basic and file flow other streams almost, mainly used in the program need to use temporary files, close the memory stream is invalid so do not shut down Operation Flow, no

1. Read the example carefully : Enumtest.java, run it, analyze the running results? public class Enumtest {public static void Main (string[] args) {Size S=size.small;Size T=size.large; S and T refer to the same object?System.out.println (s==t); is

The first step, the system prompts to enter the number of participants.The second step is to get the students ' scores and accumulate them.The third step is to find the average score and output.Import Java.util.scanner;public class Chengji{public

1. Overview of the HashSet class:(1) No guarantee of Set iteration order(2) In particular, it does not guarantee that the order is constant2. How HashSet guarantees element uniqueness(1) The underlying data structure is a hash table (an array of

JAVA_SE basics -- 42. final Modifier Do not spray ~ The final keyword can be used to modify classes, variables, and methods. It has the meaning of "This cannot be changed" or "final, therefore, the classes, variables, and Methods Modified by final

Initialization of Java instance variables This question comes from the public account (what programmers do) Push: An Object-Oriented interview question by Ctrip Java engineers The question is as follows: Find the output of the following

Spring Series Assembly BeanI. Overview containers are the core of the Spring framework. Spring containers use IOC to manage all components that constitute the application system. Spring has two different containers: BeanFactory provides the simplest

Java web project references java project Most of the current projects of the company use client and service to form a complete project. spring invoke is used for communication between the client and service, this leads to serious redundancy between