A Java package organizes Java classes into namespaces, providing a unique namespace for each type it contains. Classes in the same package can access each other’s package-private and protected members.

Simple example of java package

1. //save as Simple.java.
2. package mypack;
3. public class Simple{
4. public static void main(String args[]){
5. System.out.println(“Welcome to package”);
6. }
7. }

To add a class or interface to a package:

1. Add package myPackageName ; as the first Java statement of the source file.
2. In your development directory, store the source file in a directory structure corresponding to your package name.

How to Create a package?

1. Choose the name of the package.
2. Include the package command as the first line of code in your Java Source File.
3. The Source file contains the classes, interfaces, etc you want to include in the package.
4. Compile to create the Java packages.

How to create package in Java

1. First create a directory within name of package.
2. Create a java file in newly created directory.
3. In this java file you must specify the package name with the help of package keyword.
4. Save this file with same name of public class.
5. Now you can use this package in your program.

exit() method exits current program by terminating running Java virtual machine. This method takes a status code. A non-zero value of status code is generally used to indicate abnormal termination.

exit() in Java Web application, which runs inside either web server or application server, which itself is Java program is not a good idea at all. Why? because invoking System. exit() kills your JVM, invoking this from Tomcat or Jetty, will not only kill your application but the most likely server itself.

Throwing an Exception is generally considered the other alternative. Throwing exceptions is the best way to send information about a certain error up and out of the app. It’s frowned upon for normal exits. If “not everything is going according to plan”, then System.

System. exit should be used with care. The normal method of terminating a program is to terminate all user threads. Here, the program may be terminated by calling System.

2 Answers. “Best Practice” actually grounds on what on you want to execute. If you really do wish to terminate the program immediately, rather than letting upper levels of the program decide what to do, you should call: System. exit(1) (or some other non-zero positive exit status).

Shutdown Hooks are a special construct that allows developers to plug in a piece of code to be executed when the JVM is shutting down. This comes in handy in cases where we need to do special clean up operations in case the VM is shutting down.

2 Answers. When the main thread returns (i.e., you return from the main function), it terminates the entire process. This includes all other threads. The same thing happens when you call exit .

As long as the main-method thread or any other user thread remains alive, your application will continue to execute. In your case, the threads are user threads and hence are allowed to complete before the main thread exits.

Detaching Threads Separates the thread of execution from the thread object, allowing execution to continue independently. Any allocated resources will be freed once the thread exits.

There is no way to cleanly shutdown a detached thread. Doing so would require waiting for the cleanup to complete, and you can only do that if the thread is joinable. Consider, for example, if the thread holds a mutex that another thread needs to acquire in order to cleanly shut down.

thread::detach Separates the thread of execution from the thread object, allowing execution to continue independently. Any allocated resources will be freed once the thread exits. After calling detach *this no longer owns any thread.

Do not join or detach a thread that was previously joined or detached. The C Standard, 7.26. 5.6 [ISO/IEC 9899:2011], states that a thread shall not be joined once it was previously joined or detached. 5.3 states that a thread shall not be detached once it was previously joined or detached.

std::thread is the thread class that represents a single thread in C++. To start a thread we simply need to create a new thread object and pass the executing code to be called (i.e, a callable object) into the constructor of the object.

std::thread Threads allow multiple functions to execute concurrently. std::thread objects may also be in the state that does not represent any thread (after default construction, move from, detach, or join), and a thread of execution may not be associated with any thread objects (after detach).

Now it is quite easy to modify a by reference bounded std::shared_ptr in a thread-safe way. The update of the std::shared_ptr ptr (1) is thread-safe.