foreword
In Java, having multi-threading capability is one of its great strengths. However, have you ever wondered how to start a thread in Java? This involves a mysterious method - start0(). Let's unravel this mystery together and explore start0()the concrete implementation of the method.
What is start0()the method?
First, let's be clear: start0()a method is a native method provided by the Java Virtual Machine (JVM). Native methods refer to platform-specific code provided by the underlying computer system, usually written in C or C++. Java implements interaction and operation with the underlying system through native methods.
start0()ThreadA method is a private method of a class in Java that is used to start a thread.
start0()Method call process
When we create a thread object in Java and start()start the thread by calling a method, we actually start()call start0()the method indirectly through the method.
Specifically, start()the method starts the execution of a new thread by calling a native method start0(). start()The method is responsible for some preprocessing work, such as checking and setting the thread status. It will then call start0()methods to do the actual thread startup.
start0()local implementation of the method
Since start0()the method is a native method, its specific implementation depends on the implementation of the Java virtual machine. Different JVM implementations may handle thread creation and startup in different ways.
However, in a typical JVM implementation, start0()the method does the following:
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First, it checks whether the state of the current thread object allows it to start. If the state of the thread object does not meet the start conditions,
start0()the method will throw anIllegalThreadStateExceptionexception. -
Next,
start0()the method allocates the required system resources and memory space for the new thread. This includes creating a separate execution environment and stack space for the thread. -
Once the system resources and memory allocation are complete,
start0()the method will call the native function provided by the operating system in order to create a real operating system level thread. This native function may be an API based on the platform, such as WindowsCreateThread()or Linuxpthread_create(). -
Finally,
start0()the method updates the state of the thread object and adds the thread to the thread scheduler so that it can be scheduled for execution.
Precautions
Although we have start0()discussed the specific implementation of the method, it is important to remember that this method is an internal detail of the Java virtual machine, and we usually do not need to directly manipulate it. We should use start()methods to start threads instead of calling them directly start0().
Also, since start0()the method is a native method, its behavior and effects may vary in different Java versions and on different platforms. Therefore, when writing cross-platform Java code, you should follow the principle of platform independence and try to avoid relying on specific underlying behaviors.
Summarize
start0()Through this article, we have gained a deeper understanding of methods in Java . As one of the key steps in thread startup, this native method is responsible for allocating resources, creating operating system-level threads, and performing state updates. Although we usually don't need to manipulate it directly, understanding its implementation details can help us better understand the Java multithreading mechanism.
Whether you are a novice or an experienced Java developer, exploring the implementation details of Java internals is always an interesting and rewarding journey. Now that we have a more comprehensive understanding of Java's thread startup process, let's continue to learn and create!