Programmer Group

1. Definition of reflection Java reflection mechanism is a reflection mechanism of Java language that can know all the properties and methods of any class in the running state of a program, and can call any method and property of any object. This kind of dynamic information acquisition and function ...

@Transactional attribute The @Transactional annotation can only be applied to public modifiers and will not work with other modifiers without error. @Transactional ly is typically added to an implementation class or implementation class method, not to an interface or interface method. @Transaction ...

1, Loading mechanism of class The loader loading of classes in Java comes from files, networks, source files, etc. By default, the class loader of the jvm uses the parent delegation mechanism, Bootstrap ClassLoader, Extension ClassLoader, and attachment classloader (system classloader). Each class l ...

Yesterday we looked briefly at the use of Unsafe. Today we look at how atoms in JUC use Unsafe and how they work!   1. Simple use of AtomicLong Also remember that in the last blog we used the volatile keyword to modify a variable of type int, and then two threads did 10,000 + 1 operations on the variable, and the result wasn't 20,000. Now when ...

Character string Literal amount of string: refers to the string itself, such as "Java", "Hello". String object: for example, new String("abc") or direct String s="str". The following "str" is also a string object. String reference: a reference is a variable that points to the corresponding stri ...

Recently, I revisited Java enumeration and saw this article that I thought was good, so I simply translated and improved some content and shared it with you. I hope you can also get something. In addition, don't forget that there is a supplement at the end of the article! ps: here is an enumeration article, which is also a very practical pract ...

Catalog 1, purpose 2. Practice (jdk8) 2.1 Java heap overflow 2.2 virtual machine stack and local method stack overflow 2.3 method area and runtime constant pool overflow 2.4 local direct memory overflow Reference resources 1, purpose Verify the contents stored in each runtime area described ...

By analyzing these two usages, we can understand the concept of lock in java. One is instance lock (lock on an instance object, if the class is a single instance, then the lock also has the concept of global lock). The other is global lock (the lock is for a class, no matter how many objects are instance, then the thread shares the lock). The i ...

Single case mode: That is to say, in the whole life cycle, the production of this object is always the same, unchanged. It ensures that a class has only one instance and provides a global access point to access it. Effect: When thread safety is required, the uniqueness and thread safety of class instances are guaranteed. When multiple instan ...

execute(String  sql)    Any sql statement can be executed, but the return value is void, so it is generally used for database creation, modification, deletion and data table record addition, deletion and modification.     int  update(String sql)  int  update(String sql, Object...args) Add, delete, args passes the actual parameter, and retur ...