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In this article Xiaobian for you to introduce in detail "what are the common problems of the static keyword in Java", the content is detailed, the steps are clear, and the details are handled properly. I hope that this article "what are the common problems of the static keyword in Java?" the article can help you solve your doubts.

1. What does static mean?

The static keyword indicates that a member variable or member method can be accessed without an instance variable of the class to which it belongs.

For example

Main class

Package com.xiao;/** * @ author: Xiao Xiao * @ date: Created in 2022-3-11 12:37 * / public class Main {public static int f = 10; public static void show () {System.out.println ("static method calls: the value of f is" + f);}}

Testing method

Import com.xiao.Main;public class Test {public static void main (String [] args) {System.out.println ("static variable:" + Main.f); Main.show ();}}

Output result

Static variable: 10

Static method call: the value of f is 10

From the above example, we can find that we can call variables and methods decorated by static in the Main class without creating an object instance. So the static keyword indicates that a member variable or member method can be accessed without an instance variable of the class to which it belongs.

2. Why use the static keyword?

In the following two cases, the static keyword meets our needs.

Generally speaking, when you create an object of a class with new, the data storage space is allocated and the method is called by the outside world. But sometimes we just want to allocate a single storage space for a particular domain, regardless of how many objects to create or none at all.

Then we want to use variables and call methods without creating an object.

3. Is it possible to override a private or static method in Java?

The static method in Java cannot be overridden because the method override is based on runtime dynamic binding, while the static method is statically bound at compile time (that is, when the class is loaded by the Java virtual machine, the static method is loaded with the same class, so the static method belongs to the class and is statically bound at compile time). The static method is not relevant to any instance of the class, so it is not conceptually applicable.

4. Can I access non-static variables in the static environment?

The static variable belongs to the class in Java, and its value is the same in all instances. The static variable is initialized when the class is loaded by the Java virtual machine. If your code tries to access non-static variables without instances, the compiler will report an error because the variables have not been created and have not been associated with any instances.

5. Can static static methods refer to non-static resources?

I can't. That is, when the class is loaded by the Java virtual machine, the static method will be loaded and initialized with the same class, so the static method belongs to the class. Instead of static resources, they will be created only after the corresponding instance has been created. The class loading and initialization process occurs before the instance object is created, so an error is reported if the static method references a non-static resource that does not exist at all.

6. Can static resources be referenced in static static methods?

Yes. Because when the class is loaded by the Java virtual machine, the static static methods and static resources will be loaded and initialized with the same class, so the static static methods can access the corresponding static resources. So static resources can be referenced in static static methods.

7. Can static resources be referenced in non-static methods?

Yes. Because static resources are loaded and initialized when the class is loaded by the Java virtual machine, while non-static methods are created and initialized when instance objects are created, the corresponding static resources already exist when non-static methods are created and initialized. So static resources can be referenced in non-static methods.

8. What is the order in which java static variables, code blocks, and static methods are executed?

Code block execution order: static code block-- > construction code block-- > constructor-- > ordinary code block

The order of code block execution in inheritance is: parent class static block-> subclass static block-> parent class construction code block-> parent class constructor-> subclass construction code block-> subclass constructor.

Main class

Package com.xiao;/** * @ author: Xiao Xiao * @ date: Created in 2022-3-11 12:37 * / public class Main {private Integer a; / / static code block static {System.out.println ("static code block....");} / / no parameter constructor public Main () {System.out.println ("no parameter constructor....") } / / Parametric Construction public Main (Integer a) {this.a = a; System.out.println ("Parametric Constructor....");} / / Construction Code Block {System.out.println ("Construction Code Block....") } / / ordinary initialization block public void method () {System.out.println ("ordinary initialization block....");}}

Test class

Import com.xiao.Main;public class Test {public static void main (String [] args) {Main main = new Main (); main.method ();}}

Test result

Static code block.

Construct a code block.

No parameter constructor.

General initialization block.

After reading this, the article "what are the common problems of static keywords in Java" has been introduced. If you want to master the knowledge points of this article, you still need to practice and use it yourself. If you want to know more about related articles, please follow the industry information channel.

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