I need some help

Pytania dotyczące zadania

Numeral system converter

Wielowątkowość w Java, Poziom 10, Lekcja 2

Rozwiązane

it seems to work properly, I have a problem with verifying the number system,

Implement the convertNumberToOtherNumberSystem method, which should convert number.getDigit() from one number system (numberSystem) to another (expectedNumberSystem).
Throw a NumberFormatException if the passed number is invalid, e.g. the number "120" passed with the binary number system.
Check that number.getDigit() is not negative.
The main method is not tested.

Wymagania:

There must be a convertNumberToOtherNumberSystem(Number, NumberSystem) method that returns a Number.
A NumberFormatException should be thrown if the number passed is invalid for the specified number system.
You need to correctly implement the convertNumberToOtherNumberSystem method: convert the number to the specified number system.
The NumberSystemType enum must support the NumberSystem interface.
The NumberSystemType enum must have 11 values representing number system bases. Here are the bases: 2, 3, 4, 5, 6, 7, 8, 9, 10, 12 and 16.

package com.codegym.task.task30.task3001; /* Numeral system converter */ import java.util.LinkedHashMap; public class Solution { public static void main(String[] args) { Number number = new Number(NumberSystemType._10, "6"); Number result = convertNumberToOtherNumberSystem(number, NumberSystemType._2); System.out.println(result); // 110 expected number = new Number(NumberSystemType._16, "6df"); result = convertNumberToOtherNumberSystem(number, NumberSystemType._8); System.out.println(result); // 3337 expected number = new Number(NumberSystemType._16, "abcdefabcdef"); result = convertNumberToOtherNumberSystem(number, NumberSystemType._16); System.out.println(result); // abcdefabcdef expected } public static Number convertNumberToOtherNumberSystem(Number number, NumberSystem expectedNumberSystem) { // Map with key as string for number and value as int LinkedHashMap<String, Integer> map = new LinkedHashMap<>(); int numberSystem = number.getNumberSystem().getNumberSystemIntValue(); int expectedSystem = expectedNumberSystem.getNumberSystemIntValue(); // sFCNS - Help string For Checking Number System String sFCNS = "0123456789abcdef"; // arraysFCNS and intsArrayFCNS,temporary help arrays with String and Integer for data String [] stringsArrayFCNS = sFCNS.split(""); int [] intsArrayFCNS = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 }; // Loop to put data in map from arraysFCNS and intsArrayFCNS for (int i = 0; i < stringsArrayFCNS.length; i++) { map.put(stringsArrayFCNS[i], intsArrayFCNS[i]); } // Check if number is in correct system String temp = sFCNS.substring(numberSystem); boolean check = false; if (!temp.equals("")){ for (int i = 0; i < temp.length(); i++){ char letter = temp.charAt(i); if (number.getDigit().toLowerCase().contains(String.valueOf(letter))) { check = true; break; } } if (check){ throw new NumberFormatException(); } } StringBuilder sb = new StringBuilder(); if (expectedNumberSystem.getNumberSystemIntValue() == number.getNumberSystem().getNumberSystemIntValue()){ return new Number(expectedNumberSystem, number.getDigit()); }else { int result = 0; // Convert to 10 system for (int i = 0; i < number.getDigit().length(); i++){ int num = map.get(number.getDigit().substring(i, i + 1)); result = result * numberSystem + num; } // Convert to expected system while (result > 0) { int rest = result % expectedSystem; sb.insert(0, rest); result = result / expectedSystem; } } return new Number(expectedNumberSystem,sb.toString()); } }

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Krystian

Poziom 32 , Poland, Poland

30 maja, 18:03

and i find new bug in my code:)

Thomas

Poziom 41 , Bayreuth, Germany

31 maja, 15:22

rozwiązanie

Is it working now? I'd start with checking if the number is null, if not, then if number.digit is null or empty. If any is true throw the exception before checking the next. And here a quick way to check for a valid number (after doing the null checks). That approach will also mark empty strings as false.

String validNumberRegex = "[" +
        "0123456789abcdef".substring(0, /* the number system, eg. octal */ 8) +
        "]+"; // results in [01234567]+

String octalNumber = "1337"; // valid octal number
System.out.println(octalNumber.matches(validNumberRegex));

Krystian

Poziom 32 , Poland, Poland

1 czerwca, 13:41

The first issue I notice is that the second loop for converting to the desired system needs to use a map, otherwise I will only have numbers in base 12 and 16. The second problem is determining which system is 12 and which is 16, for example for numbers like 9a, it will never work. I noticed that someone used a switch statement only for the example in the main method and it works, I would like to do it from the bottom up so that it works every time for every code.

Thomas

Poziom 41 , Bayreuth, Germany

1 czerwca, 14:04

rozwiązanie

The tasks does not ask you to determine the number system. That's given when a Number is created. You just have to get it using Number:getNumberSystem(). That'll return a NumberSystem Object with a NumberSystem:getNumberSystemIntValue() method that'll return an int (the number system int value). That resulting int you can use inside my code snippet above to get a regex to validate the number.

Krystian

Poziom 32 , Poland, Poland

1 czerwca, 14:52

validation this point off task works thx Thomas, now i have to fix problem with second loop:)

Thomas

Poziom 41 , Bayreuth, Germany

1 czerwca, 15:09

rozwiązanie

You mean that one?

while (result > 0) {
    int rest = result % expectedSystem;
    sb.insert(0, rest);
    result = result / expectedSystem;
}

rest is the decimal value of the number system you want to convert to. If you eg. convert to hex, then this can range from 0 to 15. This you look up in your array (or sFCNS String, like sFCNS.charAt(rest)) and you get the char you need to add to your result String(Builder)... your variable naming is not that self speaking :) ... rest could be named smth like currentDigit, result maybe num or number and sb is the result or convertedNumber. Oh, and I also used BigInteger to be able to hold big numbers and not just 2*10^9 Second oh, BigInteger has build in base conversion (but I didn't use it and coded my own algorithm).

Krystian

Poziom 32 , Poland, Poland

1 czerwca, 15:34

thx again, BigInteger was solution, this task was not so easy but i have a lot of fun to resolve, and still i use my loops to convert numbers