JVM- What classes are loaded by various loaders? (class loader sphere) https://yuhongliang.blog.csdn.net/article/details/111566140 class loading process analysis:

LoadClass () loads any class

package com.yuhl.c2020;

/ * * *@author yuhl
 * @Date2020/12/22 use *@Classname LoadClassResource
 * @Description TODO
 */
public class LoadClassResource {
    public static void main(String[] args) throws ClassNotFoundException {
        Class clazz = LoadClassResource.class.getClassLoader().loadClass("com.yuhl.c2020.Miao"); System.out.println(clazz.getName()); }}Copy the code

LoadClass () source code analysis

   publicClass<? > loadClass(String name)throws ClassNotFoundException {
        return loadClass(name, false);
    }
Copy the code

LoadClass (String name, Boolean resolve)

// name = com.yuhl.c2020.Miao
protectedClass<? > loadClass(String name,boolean resolve)
        throws ClassNotFoundException
    {
    // The lock is placed before the call, indicating thread-safe
        synchronized (getClassLoadingLock(name)) {
            // First, check if the class has already been loaded
            // Check whether memory already exists (already loaded)Class<? > c = findLoadedClass(name);// If the cleavage is not loaded, perform the following operations
            if (c == null) {
                long t0 = System.nanoTime();
                try {
	                // If not, the parent member variable of the current class loader is passed up to start the parent delegate
	                // If parent is not empty, parent resets the method
                    if(parent ! =null) {
                        c = parent.loadClass(name, false);
                    } else {
                    	Private native Class
       findBootstrapClass(String name); There are JVM calls to handlec = findBootstrapClassOrNull(name); }}catch (ClassNotFoundException e) {
                    // ClassNotFoundException thrown if class not found
                    // from the non-null parent class loader
                }

				// If it is still not loaded, there is a findClass () method
                if (c == null) {
                    // If still not found, then invoke findClass in order
                    // to find the class.
                    FindClass (); /** findClass(); protected Class
       findClass(String name) throws ClassNotFoundException { throw new ClassNotFoundException(name); } * /
                    long t1 = System.nanoTime();
                    c = findClass(name);

                    // this is the defining class loader; record the statssun.misc.PerfCounter.getParentDelegationTime().addTime(t1 - t0); sun.misc.PerfCounter.getFindClassTime().addElapsedTimeFrom(t1); sun.misc.PerfCounter.getFindClasses().increment(); }}if (resolve) {
                resolveClass(c);
            }
            returnc; }}Copy the code

4. To summarize