??????? static????????
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public class User {
private static int userNumber  = 0 ;
public User(){
userNumber ++;
}
public static void main(String[] args) {
User user1 = new User();
User user2 = new User();
System.out.println("user1 userNumber??" + User.userNumber);
System.out.println("user2 userNumber??" + User.userNumber);
}
}
------------
Output:
user1 userNumber??2
user2 userNumber??2
???????? ??????static
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????ClassName.propertyName
????ClassName.methodName(……)
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????2.1??static????
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????2.2??static????
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