Another interview question about inheritance

topic description

public class Base {

private String baseName = "base";

public Base() {
    callName();
}

public void callName() {
    System.out.println(baseName);
}

static class Sub extends Base {
    private String baseName = "sub";

    public void callName() {
        System.out.println(baseName);
    }
}

public static void main(String[] args) {
    Base b = new Sub();
}

}

what result do you expect? What is the error message actually seen?

Why output: null?

Java
Dec.17,2021 
public class Base {

private String baseName = "base";//1

public Base() {
    callName();//2
}

public void callName() {
    System.out.println(baseName);
}

static class Sub extends Base {
    private String baseName = "sub";

    public void callName() {
        System.out.println(baseName);//3
    }
}

public static void main(String[] args) {
    Base b = new Sub();
}
}

Base b = new Sub (); initializes the parent class first, in the order like 1dint 2 new Sub (); 3 above. When entering the callName method, the properties of the subclass have not yet initialized the execution code, so what is printed is null.

.

Previous: ECONNREFUSED error occurs when npm installs electron

Next: Why do I call store.dispatch (loading (55) to initialize other action as well?

css mysql arrays josn react html typescript webpack npm sass R objective-c .net sql-server jquery python-3.x angularjs django angular excel regex iphone ajax linux xml pandas vba spring database wordpress string wpf xcode windows bash postgresql oracle multithreading eclipse list firebase algorithm macos forms image scala visual-studio azure bootstrap spring-boot react-native python-2.7 docker performance function winforms matlab powershell apache dataframe api sqlite numpy rest shell selenium flutter dart maven loops qt swing android-studio csv express file class tensorflow sorting codeigniter perl
MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1e564d7-44318.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1e564d7-44318.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
Need Help?