What are the common methods of java class loader

1. loadClass, When a class loading request comes, first find the class object from the cache.

If there is a direct return, if not, it is handed over to the parent loader of this type of loading. If there is no parent to load, it is loaded by the top-level boot loader. If it is still not found, use findClass() to load it;

2. FindClass

Load the Class bytecode by name or position, and then use defineClass, usually by subclass Class implementation, if you need to customize ClassLoader, you must override this method.

3. The defineClass

defineClass() method parses the byte stream into a Class object that can be recognized by the JVM (the logic of this method has been implemented in ClassLoader). This method can not only instantiate class objects through class files, but also instantiate class objects through other methods. For example, receiving a type of bytecode through the network and then converting it into a byte byte stream to create the corresponding Class object, while defineClass( ) method is usually used together with the findClass() method. Usually when customizing a class loader, you will directly override the findClass() method of the Classloader and write the loading rules. After obtaining the bytecode of the class to be loaded, convert it into a stream, and then call defineClass. The () method generates the Class object of the class, which simply converts the classes file into a Class object.

4. resolveClassAfter the creation of the Class object, it can also be resolved at the same time.

We said before that the link phase mainly verifies the bytecode, allocates memory, sets class variables, and converts symbol references in the bytecode file into direct references.

What are the advantages of Java

1. Simple, as long as you understand the basic concepts, you can write applications suitable for various situations; 2. Object-oriented; 3. Distribution, Java is a network-oriented language; 4. Robustness, Java provides automatic garbage collection for memory management, preventing programmers from making errors when managing memory. ; 5. Security. Java used in network and distributed environments must prevent virus intrusion. 6. Architecture neutral, as long as the Java runtime system is installed, it can run on any processor. 7. Portability, Java can be easily transplanted to different machines on the network. 8. Interpretation and execution, the Java interpreter directly interprets and executes the Java bytecode.

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