Think about that your colleague from the IT division is engaged on a brand new chatbot utility implementing—amongst some others—the Command design sample. The bot’s command objects are created as soon as upon startup and reused by means of the lifetime of the applying. Under is the partial code of the applying, particularly, the AboutCommand interface, which should return the textual content Copyright (c) 2023, http://mycompany.com.
public interface Command {
String execute(Context c);
}
public class AboutCommand implements Command {
non-public String url;
public AboutCommand(String s) {
url = s;
}
public String execute(Context c) {
url = url.substring(0, url.lastIndexOf(“https://oraclejavacertified.blogspot.com/”)); // line 2
url = url.substring(0, url.lastIndexOf(“https://oraclejavacertified.blogspot.com/”)); // line 3
return “Copyright (c) 2023, ” + url; // line 4
}
}
public class ChatBot {
public static closing String HOME_PAGE = “http://mycompany.com/botapp/index.html”;
non-public closing Command about;
ChatBot() {
about = new AboutCommand(HOME_PAGE);
… // create some extra instructions
}
}
Which assertion is right? Select one.
A. The code is compilable and works as anticipated.
B. The code just isn’t compilable. To repair the code, the ultimate modifier on the variable HOME_PAGE have to be eliminated.
C. The code is wrong. To repair it, modify traces 2 and three like this:
url.substring(0, url.lastIndexOf(“https://oraclejavacertified.blogspot.com/”)); // line 2
url.substring(0, url.lastIndexOf(“https://oraclejavacertified.blogspot.com/”)); // line 3
D. The code is wrong. To repair it, modify traces 2 and three like this:
var url = this.url.substring(0, this.url.lastIndexOf(“https://oraclejavacertified.blogspot.com/”)); // line 2
url = this.url.substring(0, this.url.lastIndexOf(“https://oraclejavacertified.blogspot.com/”)); // line 3
E. The code is wrong. To repair it, modify traces 2 and three like this:
var url = this.url.substring(0, this.url.lastIndexOf(“https://oraclejavacertified.blogspot.com/”)); // line 2
url = url.substring(0, url.lastIndexOf(“https://oraclejavacertified.blogspot.com/”)); // line 3
Reply. This query investigates elements of string manipulation, native and occasion variables, and logical considering.
To start with, possibility A is wrong. Whereas the primary name of the execute() technique will return the required textual content, the tactic has unintended effects. Particularly, it modifies the occasion variable. Due to this fact, a second name will return solely Copyright (c) 2023, http:. A 3rd name will throw java.lang.StringIndexOutOfBoundsException.
To right this, you could possibly both recalculate the message every time with out altering the worth of the sphere named url, or you could possibly calculate the message as soon as and retailer the outcome for future use. The latter can be extra environment friendly. Let’s examine the opposite choices to see if any obtain this outcome.
Possibility B is wrong and fully irrelevant to the issue you have got. At no level does any of the code proven within the query try and reassign the HOME_PAGE fixed, so the ultimate modifier can’t be the reason for any issues.
Possibility C can be incorrect. It avoids reassigning the url discipline, which looks like a step ahead. Nonetheless, strings are immutable, so line 4 will return the preliminary unchanged worth. Line 2 will create a brand new string containing the textual content http://mycompany.com/botapp, however that string is instantly deserted as a result of the reference to it (which is carried because the return worth of the lastIndexOf technique) just isn’t saved wherever. Line 3 merely repeats the method, and the brand new string is deserted once more. Due to this fact, the outcome will likely be Copyright (c) 2023, http://mycompany.com/botapp/index.html.
As well as, possibility D is wrong. It introduces a brand new native variable, String url. Line 2 creates a brand new string (as in possibility C) by eradicating the /index.html half from the unique textual content. This new string is saved within the native variable known as url. Nonetheless, line 3 merely repeats the habits of line 2, as a result of it reads its beginning worth from the sphere known as url, not the worth created by line 2. Consequently, this model produces the message Copyright (c) 2023, http://mycompany.com/botapp.
Possibility E is right. Traces 2 and three each retailer the results of their operations, and line 3 makes use of the results of line 2 as its place to begin. In consequence, the code cuts off two parts from the url: /index.html first after which /botapp. Critically, this code doesn’t modify the occasion variable, so every subsequent run of the execute() technique will return the specified textual content: Copyright (c) 2023, http://mycompany.com.
To be clear, this isn’t an environment friendly method to coding this drawback. It could be higher to calculate the outcome as soon as and retailer it for reuse. The next code, used as a constructor for the AboutCommand class, would obtain that:
public AboutCommand(String s) {
url = s.substring(0, s.lastIndexOf(“https://oraclejavacertified.blogspot.com/”));
url = url.substring(0, url.lastIndexOf(“https://oraclejavacertified.blogspot.com/”));
url = “Copyright (c) 2023, ” + url;
}
Given this initialization, the execute technique would merely seem like the next:
public String execute(Context c) {
return url;
}
There’s a closing observe to say right here. Had been you questioning about that constructor argument Context c? In quiz questions, you need to assume that there’s sufficient code surrounding what’s proven, or sufficient context, to permit the code to work if it may work. If there’s an issue you might be anticipated to acknowledge, it’ll be within the code you might be proven, not in one thing that’s not proven.
Conclusion. The right reply is possibility E.
Supply: oracle.com
