Optimization skills of the core JVM framework in the Java class library
Optimization skills of the core JVM framework in the Java class library
The Java virtual machine (JVM) is the basis of the Java program and the core of the entire Java class library.Optimizing the JVM framework can significantly improve the performance and efficiency of the Java application.This article will introduce some skills to optimize the JVM framework to help developers better use the core functions in the Java class library.
1. Reasonable setting JVM's heap memory
The heap memory of JVM is the key part of the Java program when running. It can optimize the performance of JVM by setting-XMX (maximum pile memory) and -xms (initial heap memory) parameters to reasonable values.By default, JVM will automatically allocate heap memory according to the physical memory of the current system, but this may not be enough to meet the needs of large applications.Therefore, developers can manually set the size of the heap memory according to the actual situation to achieve the best performance.
Example code:
java -Xmx2g -Xms512m MyApp
2. Use the appropriate garbage collector
Java provides a variety of garbage collectors, such as serial collectors, parallel collectors and concurrent collectors.According to the needs of the application, choosing a suitable garbage collector can improve the performance of JVM.For applications that need to minimize garbage collection, you can consider using parallel or concurrent collectors.For the environment with limited resources, choosing a serial collector may be more suitable.
Example code:
java -XX:+UseG1GC MyApp
3. Use the local method to call
In the Java class library, some functions need to rely on the French library to achieve, such as file I/O, network communication, etc.Using a local method, you can bypass the JVM interpreter and JIT compiler, and directly call the local code to improve the execution efficiency of the program.However, pay attention to safety and portability problems when using local methods.
Example code:
public class NativeMethodExample {
// Local method declaration
native void nativeMethod();
public static void main(String[] args) {
NativeMethodExample example = new NativeMethodExample();
example.nativeMethod();
}
// Load the Library of this area
static {
System.loadLibrary("nativeLibrary");
}
}
4. Optimize hot code using JIT compiler
The JIT compiler can compile the frequently running code of the machine to improve the execution speed of the program.By using the appropriate JIT compiler option, you can optimize the hot code in the JVM framework and improve the overall performance.For example, you can observe the optimization of the hot spot code by setting the JIT compiler by setting the -xx:+PrintCompiLATION parameter.
Example code:
java -XX:+PrintCompilation MyApp
5. Optimize the creation and destruction of objects
In the Java class library, the creation and destruction of objects is a common operation.In order to improve the performance of JVM, some optimization strategies can be adopted, such as the object pool, cache or delay initialization.This can reduce the frequent creation and destruction of the object, thereby improving the efficiency of the Java application.
Example code:
public class ObjectPoolExample {
private static final int MAX_POOL_SIZE = 10;
private static List<Object> objectPool = new ArrayList<>();
static {
for (int i = 0; i < MAX_POOL_SIZE; i++) {
objectPool.add(new Object());
}
}
public static Object getObjectFromPool() {
if (objectPool.isEmpty()) {
return new Object();
} else {
return objectPool.remove(0);
}
}
public static void releaseObjectToPool(Object obj) {
if (objectPool.size() < MAX_POOL_SIZE) {
objectPool.add(obj);
}
}
public static void main(String[] args) {
Object obj1 = ObjectPoolExample.getObjectFromPool();
// user target audience...
ObjectPoolExample.releaseObjectToPool(obj1);
}
}
In summary, through the reasonable setting of JVM pile memory, choosing appropriate garbage collectors, using local methods, optimizing hot codes, and the creation and destruction of optimized objects, you can optimize the core JVM framework in the Java library library to optimize, Improve the performance and efficiency of Java applications.In actual development, developers can choose appropriate optimization methods according to specific needs, and combine performance testing for evaluation and adjustment.
