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This article mainly introduces "what are Java's advanced interview questions". In daily operation, I believe many people have doubts about Java's advanced interview questions. Xiaobian consulted all kinds of materials and sorted out simple and easy operation methods. I hope to help you answer the doubts of "Java's advanced interview questions"! Next, please follow the small series to learn together!

Memory structure of JVM

According to JVM specifications, JVM memory is divided into five parts: virtual machine stack, heap, method area, program counter and local method stack.

1. Java Virtual Machine Stack:

Thread private; each method creates a stack frame when executed, storing local variable tables, operand stacks, dynamic connections, method return addresses, etc.; each method from invocation to execution is completed, corresponding to a stack frame in the virtual machine stack push and pop stack.

2. Stack:

Thread sharing; an area of memory shared by all threads, created at virtual machine startup, used to hold object instances.

3. Method area:

Thread sharing; an area of memory shared by all threads; used to store class information, constants, static variables, etc. that have been loaded by the virtual machine.

4. Program counter:

Thread private; is a line number indicator of the bytecode executed by the current thread, each thread must have a separate program counter, this type of memory is also called "thread private" memory.

5. Local method stack:

Threads are private; primarily Native method services used by virtual machines.

The general answer is as above. Please move similar articles:

Memory partition of JVM

JVM knowledge points combing

JVM memory allocation and reclamation

JVM memory management mechanism

The difference between strong, soft and weak references

Strong quote:

Only after the reference is deallocated will the object be deallocated. As long as the reference exists, the garbage collector will never collect it. This is the most common new object.

Soft references:

References recycled through code prior to memory overflow. Soft reference is mainly used by users to implement similar cache functions. When there is enough memory, the soft reference can directly take values without querying data from busy real sources, which improves the speed. When there is insufficient memory, this part of cached data is automatically deleted and the data is queried from real sources.

Weak references:

The reference collected in the second garbage collection can be retrieved by weak reference in a short time. When the second garbage collection is performed, null will be returned. Weak references are primarily used to monitor whether an object has been marked by the garbage collector as garbage to be collected, and can be returned by the isEnQueued method of weak references.

The general answer is as above. Please move similar articles:

How Java can effectively avoid OOM: good at using soft and weak references

How arrays are allocated in memory

1. An array of simple value types, each array member is a reference (pointer) to the space on the stack (because the memory allocation of value type variables is on the stack)

2. Reference type, array of class type, each array member is still a reference (pointer), reference to the space on the heap (because the memory allocation of the instance of the class is on the heap)

Which design patterns have been used, hand-write one (except for a single example)

Design patterns have long been summarized, see here: 23 design patterns complete summary

What is the core of springmvc, how to process the request flow, how to achieve control inversion

Core:

Control inversion and facet orientation

Request Processing Flow:

First, the user sends a request to the front-end controller, and the front-end controller decides which page controller to select for processing according to the request information (such as URL) and delegates the request to it, i.e., the control logic part of the previous controller.

2. After receiving the request, the page controller performs functional processing. First, it needs to collect and bind the request parameters to an object, and verify them. Then, it delegates the command object to the business object for processing. After processing, it returns a ModelAndView (model data and logical view name).

3. The front-end controller takes back the control right, and then selects the corresponding view for rendering according to the returned logical view name, and transfers the model data for view rendering;

The front-end controller takes back control again and returns the response to the user.

How to control inversion:

Each time we use the spring framework, we configure the xml file, which configures the id and class of the bean.

The default bean pattern in spring is single-instance, which can be created through the bean's class reference reflection mechanism.

Therefore, the spring framework creates instances for us and maintains them for us through reflection.

A needs to refer to class B, and the spring framework will pass the reference to the B instance to the member variables of A via xml.

The general answer is as above. Please move similar articles:

Understanding IOC and AOP in Spring

What is the principle of AOP in Spring?

See here: IOC principles of Spring

How mybatis handles result sets

MyBatis 'result set is implemented by reflection. Not through the get/set method. Whether or not the get/set() method is defined in the entity class, it can be received.

Congratulations if the interview only tests you on this point. If you continue to ask the process, you need to find some source code to read.

Where is Java's polymorphism?

There are two main manifestations: overloading and rewriting.

Heavy load:

Is occurred in the same class, with the same method name, mainly depends on the number of parameters, types, order of different implementation methods overloaded, return value types can be different.

Rewrite:

It occurs in two classes (parent and child), with the same method name, mainly depending on the parameters in the method, the number, the type must be the same, and the return value type must be the same.

At this point, the study of "What are the advanced interview questions of Java" is over, hoping to solve everyone's doubts. Theory and practice can better match to help you learn, go and try it! If you want to continue learning more relevant knowledge, please continue to pay attention to the website, Xiaobian will continue to strive to bring more practical articles for everyone!

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