Learn from the core JVM framework in the Java class library
Learn from the core JVM framework in the Java class library
Java virtual machine (JVM) is the core component of the Java language, which provides an environment for executing the Java bytecode.The Java class library contains many core frameworks related to JVM. These frameworks provide rich functions and APIs to help developers better manage memory, optimize performance, and achieve efficient procedures.
This article will take you to understand the core JVM framework in the Java class library, and use the Java code example to illustrate the usage and role of each framework.
1. Memory Management Framework:
The Garbage Collector in Java is the core of memory management. It is responsible for automatically release objects that are no longer used, and recycling unused memory.JVM provides a series of garbage recovery algorithms and parameter configuration options, such as Mark and Sweep, Copy, Mark and Compact and other algorithms.
Example code:
public class MemoryManagementExample {
public static void main(String[] args) {
Object obj1 = new Object();
Object obj2 = new Object();
obj1 = null;
System.gc (); // Expiring trigger garbage recovery
}
}
2. Performance Monitoring Framework (Performance Monitoring Framework):)
JVM provides some tools and interfaces for monitoring program performance. Developers can use these tools to collect and analyze the performance data of the application to optimize and debug.The main composition of the performance monitoring framework includes code analyzers, performance analysis API (Performance Profiling API), and thread analysis tools.
Example code:
public class PerformanceMonitoringExample {
public static void main(String[] args) {
long startTime = System.currentTimeMillis();
// Execute code that requires monitoring performance
long endTime = System.currentTimeMillis();
long executionTime = endTime - startTime;
System.out.println ("execution time:" + ExecutionTime + "" millisecond ");
}
}
3. Dynamic code Generation Framework (Dynamic Code Generation Framework):)
JVM provides the function of dynamic generating bytecode. Developers can create, modify and load classes through dynamic code generation frameworks to achieve flexible dynamic language characteristics.These frameworks can also be used to implement AOP (facing surface programming) technology to enhance and intercept existing methods.
Example code:
class DynamicCodeGenerationExample {
public static void main(String[] args) throws Exception {
ClassPool pool = ClassPool.getDefault();
CtClass cc = pool.makeClass("DynamicClass");
CtMethod method = CtNewMethod.make("public void sayHello() { System.out.println(\"Hello, dynamic code generation!\"); }", cc);
cc.addMethod(method);
Class<?> dynamicClass = cc.toClass();
Object dynamicObj = dynamicClass.getDeclaredConstructor().newInstance();
Method sayHelloMethod = dynamicClass.getMethod("sayHello");
sayHelloMethod.invoke(dynamicObj);
}
}
Summarize:
The core JVM framework in the Java class library provides rich functions and APIs to help developers better manage memory, optimize performance, and realize dynamic characteristics.Through in -depth understanding and flexible application of these frameworks, developers can write high -efficiency, reliable and easy to debug Java applications.
