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1. Reference in Java Reference is the bridge between heap and stack in java. If you want to access objects in the heap, you must access them through reference (except for 8 basic data types) In garbage collection, if an object is still referenced by GcRoots, it will not be recycled (strong reference). This is not absolute. It is mainly determi ...

1. Time and date 1.1 Date class Time origin in computer January 1, 1970 00:00:00 Time conversion unit 1 second = 1000 milliseconds Overview of Date class Date represents a specific time, accurate to milliseconds Date class constructor Method nameexplainpublic Date()Allocate a Date object and initialize it so that it represents the time ...

Description of how to start the process Through new processbuilder (string... Commands) Start() starts the process ProcessBuilder supports chain programming to configure the related settings of child processes redirectXXX: redirect the stream of subprocesses (standard input, standard output, error message)environment() gets the environ ...

concept In a complete event system, there are the following roles Event: describe what happened, such as request processing completed and Spring container refresh completedEvent source: the generator of an event. Any event must have an event source. For example, the event source of request processing is DispatcherServlet, and the event sour ...

1. Demand Dynamically generate word documents through word templates and data in database tables. The word operation tool itself carries word to xml (save as xml directly). However, the requirements are clear. Only word templates can be used, and users are not allowed to manually transfer from word to xml and then upload. Freemark is ...

catalogue preface Lead two-way circular linked list 1. Concept 2. Effect display diagram 3. Interface implementation 3.01. The interface to be implemented in this article ​3.02. Implementation of double linked list 3.03. Initialization of double linked list 3.04. Print linked list 3.05. Dynamically apply for a node 3.06. Head ins ...

Optimization of a query You should encounter this scenario. A self incrementing primary key is set in MySQL, but some data is subsequently deleted, resulting in discontinuous primary keys. You can use the following command to query those discontinuous primary keys. -- Writing method 1 select id from (select id from Table name order by id asc ...

Annotation and reflection java.Annotation 1. What is annotation Annotation is from jdk5 New technologies introduced from 0Function of Annotation: It is not the procedure itself, which can be explained. (this is no different from comment s.)It can be read by other programs (such as compiler, etc.). Format of Annotation: Annotations ...

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1. Code area It has two characteristics: 1 is sharing, that is, we click on many of the same files, but only execute that piece of code and will not generate another piece of code. 2 is readable, that is, the code is only readable, but cannot be written, otherwise the data will be modified and the game gold coin will be changed 2. Global ...