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Thread: Help to understand the code!

  1. #1
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    Lightbulb Help to understand the code!

    Hello, everyone! I'm learning JAVA for applying to a job exam and I'd like to know what is really happening (output) in the code below that was used in a previous exam. Thank you so much for your attention and participation.

    [code = Java]
    public class Va1 {
    public static String getStr() {
    return “abcdefghijklmnop“;
    }
    public String ini(String s, int cpr) {
    return s.substring(0, cpr);
    }
    public String fin(String s, int cpr) {
    return ini(s, cpr)+s.substring(s.length()-cpr, s.length());
    }
    }
    public class Va2 extends Va1 {
    public static String getStr() {
    return “0123456789ABCDEF“;
    }
    public String ini(String s, int cpr) {
    return s.substring(s.length()-cpr, s.length());
    }
    public static void main(String[] args) {
    Va1 o=new Va2();

    System.out.println(o.fin(o.getStr(), 5));
    }
    }
    [/code]

  2. #2
    Super Moderator Norm's Avatar
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    Default Re: Help to understand the code!

    what is really happening (output)
    Can you also post the output and add some questions to it where you do not understand.
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: Help to understand the code!

    what is happening here? :

    ...
    public static void main(String[] args) {
    Va1 o=new Va2();
    ...

    I thought the getStr() would return the string "0123456789ABCDEF" instead of "abcdefghijklmnop", but I was wrong.
    Last edited by Norm; January 5th, 2023 at 06:45 PM. Reason: Fixed code tag

  4. #4
    Super Moderator Norm's Avatar
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    Default Re: Help to understand the code!

    what is happening here?
    That code defines the static method main
    Inside the method a reference variable(Va1) is declared and assigned a value (a reference to an instance of the Va2 class).

    getStr is declared as a static method. static methods should be called using the name of the class, not with a reference variable: Va1.getStr() or Va2.getStr()
    If you don't understand my answer, don't ignore it, ask a question.

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