CodeGym/Help with Java Tasks/actually have no idea what is asking about

Level 16

Springfield

16.10.2021
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9comments

actually have no idea what is asking about

Question about the task

Resolved

I think my code is pretty correct, but the only thing which could be wrong is the requirement, and it is so confusing because it doesn't give more test cases for what exactly is a right output. Need help, thx guys. My understanding is the information splits with & and will output the first line before "=", then alert(substring after "=" and before next "&" like 1v1=15 , which 1v1 will be the first line).

Read a URL from the console.
Display a space-delimited list of all the parameters (The parameters follow the "?" and are separated by "&", e.g. "lvl=15").
The URL contains at least 1 parameter.
The parameters must be displayed in the same order in which they are present in the URL.
If the obj parameter is present, pass its value to the relevant alert method.
alert(double value) - for numbers (fractional numbers have a decimal point)
alert(String value) - for strings
Note that the alert method must be called AFTER the list of all parameters is displayed.

Example 1

Input:
http://codegym.cc/alpha/index.html?lvl=15&view&name=Amigo

Output:
lvl view name

Example 2

Input:
http://codegym.cc/alpha/index.html?obj=3.14&name=Amigo

Output:
obj name double: 3.14

Requirements:

The program should read only one line from the keyboard.
The Solution class must not have static fields.
The program must display data on the screen in accordance with the task conditions.
The program should call the alert method with the double parameter if the obj parameter can be correctly converted to a double.
The program should call the alert method with the String parameter if the obj parameter CANNOT be correctly converted to a double.

package com.codegym.task.task15.task1527; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; /* Request parser */ public class Solution { public static void main(String[] args) { //write your code here try{ BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); String line = reader.readLine(); int index = indexOf(line,'?'); String temp = ""; String sum = ""; String[] split = line.substring(index+1,line.length()).split("&"); double single = 0.0; for(String a:split){ if(a.contains("=")){ String str = a.substring(0,indexOf(a,'=')); temp += str+" "; } else{ temp += a+" "; } } System.out.println(temp.trim()); for(String a: split){ if(a.contains("=") && !split[split.length-1].equals(a)){ String check = a.substring(indexOf(a,'=')+1,a.length()); if(check.contains(".")){ try{ double num = Double.parseDouble(check); alert(num); } catch(Exception e){ alert(check); } } else{ if(!Digit(check)){ alert(check); } } } } reader.close(); } catch(Exception e){ } } public static boolean Digit(String a){ for(int i = 0;i < a.length();i++){ if(!Character.isDigit(a.charAt(i))){ return false; } } return true; } public static int indexOf(String a,char b){ int index = -1; for(int i = 0;i < a.length();i++){ if(a.charAt(i) == b){ index = i; break; } } return index; } public static void alert(double value) { System.out.println("double: " + value); } public static void alert(String value) { System.out.println(value); } }

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Guanting Liu

Level 16 , Springfield, United States

17 October 2021, 19:42

Also, it abusively call alert(int) since double is also an int number by conversion hierachy which in the example, the output is not correct lol.

Guanting Liu

Level 16 , Springfield, United States

17 October 2021, 19:07

Oh, I see what's the problem. The "obj" is actually a parameter called "obj" not an object lol. It's always hard to understand english by my poor reading skills. :D

Gellert Varga

Level 23 , Szekesfehervar, Hungary

17 October 2021, 18:34

solution

Lupe raised an interesting thought: "There can also be multiple obj parameters", and you have to display the value of all of them. It was a long time ago when I solved this task, but now afterwards I got curious: does my solution fulfill this "multiple obj parameters" requirement or not? So I checked it, and the result: not. (But nevertheless my solution was accepted.) Maybe it will help you to solve the task, so I'll put here some test cases. So below you can analyse the outputs of a program that the validator once accepted. (Of course, I'm sure Lupe's code was accepted by the validator, but that probably means his code does one extra thing that the validator doesn't necessarily require.) 1.) IF INPUT: http://codegym.cc/alpha/index.html?obj=2.45&name&age=234&color=green&weight=135.8 ACCEPTED OUTPUT: obj name age color weight double: 2.45 OUTPUT OF YOUR CODE: obj name age color weight double: 2.45 green 2.) IF INPUT: http://codegym.cc/alpha/index.html?obj=someString&name&age=234&color=green&weight=135.8 ACCEPTED OUTPUT: obj name age color weight String: someString OUTPUT OF YOUR CODE: obj name age color weight someString green 3.) IF INPUT: http://codegym.cc/alpha/index.html?obj=someString&name=Amigo&obj=3.14 ACCEPTED OUTPUT: obj name obj double: 3.14 OUTPUT OF YOUR CODE: obj name obj someString Amigo 4.) IF INPUT: http://codegym.cc/alpha/index.html?obj=someString&name=Amigo&obj=3.14&weight=56 ACCEPTED OUTPUT: obj name obj weight double: 3.14 OUTPUT OF YOUR CODE: obj name obj weight someString Amigo double: 3.14 5.) IF INPUT: http://codegym.cc/alpha/index.html?length&obj&name&weight ACCEPTED OUTPUT: length obj name weight OUTPUT OF YOUR CODE: length obj name weight

Guadalupe Gagnon

Level 37 , Tampa, United States

17 October 2021, 02:14

solution

"If the obj parameter is present, pass its value to the relevant alert method." The above code only does this when obj parameter is not the last parameter in the URL. The correct output of this: "http://codegym.cc/alpha/index.html?name=Amigo&obj=3.14" is: name obj double: 3.14 There can also be multiple obj parameters. The correct output of this: "http://codegym.cc/alpha/index.html?obj=name&name=Amigo&obj=3.14" is: obj name obj String: name double: 3.14

Guanting Liu

Level 16 , Springfield, United States

17 October 2021, 02:54

Thx dude. Could u explain it a little bit deeper? So what I am confused about is the "obj" parameter. It's true that the obj parameters are seperated by & like string.split("&"), but it seems like if an object is like a = b, all the a should be printed in the first line, and then we check each of b by alert(b) one by one. So I am confused what's the problem with my code, probably i still can't understand it in English completely correct.:S

Lisa

Level 41

17 October 2021, 08:31

useful

main problem besides the issue Lupe addressed (probably) is, that you output all parameter values (if you not use the given test string and CG for sure uses a different one for validation like : http://codegym.cc/alpha/index.html?test=hoho&test2=haha&test3&obj=3.14&nameWithoutVal here just the last value won't print). But you should just print all parameter names and then only the value of the parameter with the name (if it exist) obj. So a URL may have a parameter list. That's the part after ? The parameters are divided using & Each parameter may have (besides the name) a value. The value is added after the name separated using a = http://domain?user=Joe&nextParameterWithoutValue&thirdParamButWithValue=3 url parameter (user: parameter name, Joe: parameter value) That's all... btw. I like your creative approaches. But may I ask you why you just use split once? E.g. you could split using ? as delimiter, take element 1 and split that again using & as delimiter. Loop over the result and split a third time (=). If the size is > 1, the parameter in element 0 has a value.

String line = "http://codegym.cc/alpha/index.html?test=hoho&test2=haha&test3&obj=3.14&nameWithoutVal";
for (String parameter : line.split("\\?")[1].split("&")) {
    String[] paramParts = parameter.split("=");
    System.out.format("%s - %s%n",  paramParts[0], paramParts.length > 1 ? paramParts[1] : "no value");
}

Guanting Liu

Level 16 , Springfield, United States

18 October 2021, 02:07

indexOf method is very straightforward, split doesn't make any sense really to me when there is only one "?" in the middle of a string line.

Lisa

Level 41

18 October 2021, 08:42

@Lupe PHP stores the query string in the $_GET variable. This is an associative array (stores key, value pairs). So if you use duplicate parameter names in PHP, you are biting yourself. @Guanting Liu This is only an example code, not a compulsory code. Of course you can write your programs as you like. The overhead of split however is low because it does not create new strings (neither does substring). The String class just uses references and start and end positions to store new strings created from existing ones. But you get short and clear code (and imho understandable code). Just one more if and one more sout in the above example and you already have the solution programmed (except for checking if obj is a double or not).

String line = "http://codegym.cc/alpha/index.html?test=hoho&test2=haha&test3&obj=3.14&nameWithoutVal";
String objValue = null;
for (String parameter : line.split("\\?")[1].split("&")) {
    String[] paramParts = parameter.split("=");
    System.out.print(paramParts[0] + " ");
    if (paramParts.length > 1 && paramParts[1].equals("obj"))
        objValue = paramParts[1];
}

if (objValue != null) {
    System.out.println();
    try {
        alert(Double.parseDouble(objValue));
    } catch (NumberFormatException nfe) {
        alert(objValue);
    }
}

and done... less code and eventually less errors. That's also the reason to use existing methods as theses are thoroughly tested (like the indexOf method of the String class).

Guadalupe Gagnon

Level 37 , Tampa, United States

18 October 2021, 13:12

@Lisa I was unaware of that. Thanks for the new information! My original code only used the String.split() method without any HashMaps and passed, though it called the alert() method on only the last "obj" value parameter present in the URL, as each subsequent one would over write the last, so that behavior mimicked using a HashMap.