What is the function of static modifier in Java language?

In Java classes, we often see the static keyword, which is often called static. Static modifier can be used to modify data members and method members, but it cannot modify classes (here refers to external classes) and constructors. For example:

package com.csst.vo; public class User { private String name; private static int count; public String getName() { return name; } public void setName(String name) { this.name = name; } public static int getCount() { return count; } public static void main(String[] args){ User user1=new User(); User user2=new User(); user1.setName("Rose"); user2.setName("Kate"); user1.count=10; user2.count=20; System.out.println("user1.name:"+user1.getName()+" user2.name:"+user2.getName()); System.out.println("user1.count:"+User.getCount()+"user2.count:"+user2.count); } }

The running result of this program is:

user1.name:Rose user2.name:Kate user1.count:20 user2.count:20

We can find that the name attributes of user1 and user2 are different, respectively, they are specified by calling setName for the object, and although user1 and user2 User2 specified different values for the count attribute, but the final output count values were all 20. The reason is that count is modified by static, but name is not modified by count.
Data members or method members modified by the static modifier are called static members, or class members. Those that are not modified by static are called instance members. Static members are initialized only once and are shared by all objects, so count will output two 20s. Instance members are only initialized when the object is initialized. Each time an object is created, it will be initialized once. name was initialized twice when user1 and user2 were created, so the final output is Rose and Kate.
In addition, static members, because they are shared by classes, can be called not only by objects, but also by class names. In the static method, non-static members cannot be used directly. If used, the object must be initialized and called. If there is the following code in User.java in the above example, a compilation error will occur.

public static void test(){ setName("test"); }

can be modified as follows:

public static void test(){ User user=new User(); user.setName("test"); }

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