This is probably a simple error that I am over looking but my problem is that when I am trying to return the string "roman", it just returns null.
This is the main program:
/* CCTPG-22 // Assignment 08: Roman Numerals
* #author Kevin R. Trujillo
* #version 10/28/2015
* Purpose: Converts numbers into roman numerals format and vice-a-versa
* Status:
*/
import java.util.*; // For Scanner
public class RomanMain
{
public static void main(String[] args)
{
Scanner in = new Scanner(System.in);
RomanYear year1 = new RomanYear(1975);
RomanYear year2 = new RomanYear(1988);
RomanYear year3 = new RomanYear(2007);
System.out.println(year1.toString());
System.out.println(year2.toString());
System.out.println(year3.toString());
int diff21 = year2.getYearDecimal() - year1.getYearDecimal();
int diff32 = year3.getYearDecimal() - year2.getYearDecimal();
RomanYear y2MinusY1 = new RomanYear(diff21);
RomanYear y3MinusY2 = new RomanYear(diff32);
System.out.println("Year2 minus Year1 is: " + y2MinusY1.getYearRoman());
System.out.println("Year3 minus Year2 is: " + y3MinusY2.getYearRoman());
}
// Add new methods here
} // No code can be here (outside the class)
and here is the RomanYear class:
/**
* Auto Generated Java Class.
*/
public class RomanYear {
private int decimal ;
private String roman ;
public RomanYear() // default constructor
{
decimal = 0 ;
roman = "" ;
}
public RomanYear(int newYear)
{
decimal = newYear ;
roman = setYearDecimal(decimal);
}
public RomanYear(String newYear )
{
roman = newYear ;
decimal = setYearRoman(roman) ;
}
public int setYearRoman(String roman)
{
String romanNumeral = roman.toUpperCase();
for(int x = 0;x < romanNumeral.length(); x++)
{
char convertToDecimal = roman.charAt(x);
// first step: Easy stuff
switch (convertToDecimal)
{
case 'M': decimal += 1000; break;
case 'D': decimal += 500; break;
case 'C': decimal += 100; break;
case 'L': decimal += 50; break;
case 'X': decimal += 10; break;
case 'V': decimal += 5; break;
case 'I': decimal += 1; break;
}
}
// Now adapt for specials
if (romanNumeral.contains("IV"))
{
decimal-=2;
}
if (romanNumeral.contains("IX"))
{
decimal-=2;
}
if (romanNumeral.contains("XL"))
{
decimal-=20;
}
if (romanNumeral.contains("XC"))
{
decimal-=20;
}
if (romanNumeral.contains("CD"))
{
decimal-=200;
}
if (romanNumeral.contains("CM"))
{
decimal-=200;
}
return decimal ;
}
public String setYearDecimal(int yr)
{
if (decimal > 3999)
{
System.out.println("Decimal Number: " + decimal + " is over 3999. ") ;
System.out.println("Please enter a new number") ;
System.out.println("Program is ending.............") ;
try {
Thread.sleep(2000); //5000 milliseconds is one second.
}
catch(InterruptedException ex) {
Thread.currentThread().interrupt();
}
System.exit(0) ;
}
else
{
int digit;
String roman = "";
// 1000's column
digit = yr/1000;
for (int i = 0; i < digit; i++)
roman = roman + "M";
yr = yr % 1000; // leaves 0 to 999
// 100s column
String [] hunds = {"", "C", "CC", "CCC", "CD", "D", "DC", "DCC", "DCCC", "CM"};
digit = yr/100;
roman = roman + hunds[digit];
yr = yr % 100; // leaves 0 to 99
// 10s column
String [] tens = {"", "X", "XX", "XXX", "XL", "L", "LX", "LXX", "LXXX", "XC"};
digit = yr/10;
roman = roman + tens[digit];
yr = yr % 10; // leaves 0 to 9
// Ones column
String [] ones = {"", "I", "II", "III", "IV", "V", "VI", "VII", "VIII", "IX"};
roman = roman + ones[yr];
}
return roman ;
}
public int getYearDecimal()
{
return decimal ;
}
public String getYearRoman()
{
return roman ;
}
public String toString()
{
System.out.print("Decimal: " + decimal + " as Roman Numerals is " ) ;
return roman ;
}
/* ADD YOUR CODE HERE */
}
If someone could just explain what I am doing wrong, that would be much appreciated rather than just posting the "correct way" to do it.
Thank you!
On the top of the Roman class you create a variable called roman.
public class RomanYear {
private int decimal ;
private String roman ;
In setYearDecimal you create a new variable called roman. That local variable hides the global one.
int digit;
String roman = "";
When you do roman = roman + "M"; you are only updating the local roman variable. The global one remains empty.
All you need to do is remove String from in front of the second variable.
Related
I have written a Java program to convert roman numerals into numbers. My only problem is if somebody enters "IIII" it shows up as 4, but instead it should give an error that it is not a valid roman numeral. I need to include the following rules into my code. Could anybody help me with this?
(1) No digit is repeated in succession more than thrice, i.e., I, X and C cannot be repeated more than 3 times.
(2) The digits V, L and D are not repeated. The repetition of V, L and D is invalid in the formation of numbers.
Conversion of Roman number to Decimal number:
public class RomanNumberUtils {
static String romanNumeral;
static int decimalNum;
public static void main(String args[]) {
RomanNumberUtils roman = new RomanNumberUtils();
roman .convertRomanToDecimal();
roman .printRoman(romanNumeral);
}
public void convertRomanToDecimal () {
Scanner scan = new Scanner(System.in);
System.out.print("Enter a Roman number: ");
romanNumeral = scan.nextLine();
romanNumeral = romanNumeral.toUpperCase();
int l= romanNumeral.length();
int num=0;
int previousnum = 0;
for (int i=l-1;i>=0;i--)
{
char x = romanNumeral.charAt(i);
x = Character.toUpperCase(x);
switch(x)
{
case 'I':
previousnum = num;
num = 1;
break;
case 'V':
previousnum = num;
num = 5;
break;
case 'X':
previousnum = num;
num = 10;
break;
case 'L':
previousnum = num;
num = 50;
break;
case 'C':
previousnum = num;
num = 100;
break;
case 'D':
previousnum = num;
num = 500;
break;
case 'M':
previousnum = num;
num = 1000;
break;
}
if (num<previousnum)
{decimalNum= decimalNum-num;}
else
decimalNum= decimalNum+num;
}
}
public static void printRoman (String romanNumeral){
System.out.println ("The equivalent of the Roman numeral "+romanNumeral+" is "+decimalNum);
}
}
Here's my version of a Roman numeral to decimal number converter.
Here are the test results from one of my many tests.
Enter a Roman numeral: ccccllllxxxxvvvviiii
The input Roman numeral CCCCLLLLXXXXVVVVIIII is invalid.
The correct Roman numeral is DCLXIV.
The decimal value is 664.
Enter a Roman numeral: mcmlxxii
The input Roman numeral MCMLXXII is valid.
The decimal value is 1972.
Enter a Roman numeral: mmmccclll
The input Roman numeral MMMCCCLLL is invalid.
The correct Roman numeral is MMMCDL.
The decimal value is 3450.
Enter a Roman numeral: mcmlxxio
The input Roman numeral MCMLXXIO contains invalid characters.
Enter a Roman numeral: lcl
The input Roman numeral LCL is invalid.
The correct Roman numeral is CC.
The decimal value is 200.
Enter a Roman numeral: quit
Basically, I converted the input Roman numeral into a decimal number. Then I converted the decimal number back into a Roman numeral. I compared the Roman numerals, and output the correct Roman numeral along with the decimal value.
Here's the complete runnable code.
import java.util.Scanner;
public class RomanNumeralConversion {
public static void main(String[] args) {
RomanNumeralConversion rnc = new RomanNumeralConversion();
rnc.processRomanNumerals();
}
private Object[][] conversion = { { 1000, 900, 500, 400, 100, 90,
50, 40, 10, 9, 5, 4, 1 },
{ "M", "CM", "D", "CD", "C", "XC", "L", "XL",
"X", "IX", "V", "IV", "I" } };
public void processRomanNumerals() {
Scanner scanner = new Scanner(System.in);
String inputRomanNumeral = readRomanNumeral(scanner);
while (!inputRomanNumeral.equals("QUIT")) {
int value = convertToDecimal(inputRomanNumeral);
if (value < 0) {
System.out.println("The input Roman numeral " +
inputRomanNumeral + " contains invalid characters.");
} else {
String calculatedRomanNumeral = convertToRoman(value);
if (inputRomanNumeral.equals(calculatedRomanNumeral)) {
System.out.println("The input Roman numeral " +
inputRomanNumeral + " is valid.");
} else {
System.out.println("The input Roman numeral " +
inputRomanNumeral + " is invalid.");
System.out.println("The correct Roman numeral is " +
calculatedRomanNumeral + ".");
}
System.out.println("The decimal value is " + value + ".");
}
inputRomanNumeral = readRomanNumeral(scanner);
}
scanner.close();
}
private String readRomanNumeral(Scanner scanner) {
System.out.print("Enter a Roman numeral: ");
return scanner.nextLine().trim().toUpperCase();
}
private int convertToDecimal(String input) {
int output = 0;
int index = 0;
while (index < input.length()) {
boolean isInvalid = true;
for (int i = 0; i < conversion[1].length; i++) {
String test = (String) conversion[1][i];
int j = index + test.length();
if ((j <= input.length()) &&
(input.substring(index, j).equals(test))) {
output += (Integer) conversion[0][i];
index = j;
isInvalid = false;
break;
}
}
if (isInvalid) {
return -1;
}
}
return output;
}
private String convertToRoman(int input) {
String output = "";
for (int i = 0; i < conversion[0].length; i++) {
int value = (Integer) conversion[0][i];
if (input >= value) {
output += (String) conversion[1][i];
input -= value;
i--;
}
}
return output;
}
}
I have a program that prompts the user for a string, an initial base, and a final base. The program works fine for all digits however, when I enter in a string mixed with digits and characters it does not return the correct answer. For example, when I input the string BDRS7OPK48DAC9TDT4, original base: 30, newBase: 36, it should return ILOVEADVANCEDJAVA, but instead I get ILOVEADVANHSC6LTS. I know it's a problem with my algorithm but I cant figure out why it's returning the incorrect conversion.
import java.util.Scanner;
public class BaseConversion {
public static void main(String[] args) {
Scanner s = new Scanner(System.in);
String theValue;
String result;
String newNum;
int initialBase;
int finalBase;
String[] parts = args;
if (parts.length > 0) {
theValue = parts[0];
isValidInteger(theValue);
initialBase = Integer.parseInt(parts[1]);
finalBase= Integer.parseInt(parts[2]);
isValidBase(finalBase);
}
else {
System.out.println("Please enter a value: ");
theValue = s.nextLine();
isValidInteger(theValue);
System.out.println("Please enter original base: ");
initialBase = s.nextInt();
System.out.println("Please enter new base: ");
finalBase = s.nextInt();
isValidBase(finalBase);
}
// check it
// isValidInteger(theValue, finalBase);
s.close();
newNum = convertInteger(theValue, initialBase, finalBase);
System.out.println("new number: " + newNum);
}
public static void isValidBase(int finalBase) {
if (finalBase < 2 || finalBase > 36) {
System.out.println("Error: Base must be greater than or equal to 2 & less than or equal to 36");
System.exit(1);
}
}
public static void isValidInteger(String num) {
char chDigit;
num = num.toUpperCase();
for(int d = 0; d < num.length(); d++) {
chDigit = num.charAt(d);
if (!Character.isLetter(chDigit) && !Character.isDigit(chDigit)) {
//System.out.println(chDigit);
System.out.println("Error character is not a letter or number");
System.exit(1);
}
}
}
public static String convertInteger(String theValue, int initialBase, int finalBase) {
double val = 0;
double decDigit = 0;
char chDigit;
// loop through each digit of the original number
int L = theValue.length();
for(int p = 0; p < L; p++) {
// get the digit character (0-9, A-Z)
chDigit = Character.toUpperCase(theValue.charAt(L-1-p));
// get the decimal value of our character
if(Character.isLetter(chDigit)) {
decDigit = chDigit - 'A' + 10;
}
else if (Character.isDigit(chDigit)) {
decDigit = chDigit - '0';
}
else {
System.out.println("Error d");
System.exit(1);
}
// add value to total
val += decDigit * Math.pow(initialBase, p);
}
// determine number of digits in new base
int D = 1;
for( ; Math.pow(finalBase, D) <= val; D++) {}
// use char array to hold new digits
char[] newNum = new char[D];
double pwr;
for(int p = D-1; p >= 0; p--) {
// calculate the digit for this power of newBase
pwr = Math.pow(finalBase, p);
decDigit = Math.floor(val / pwr);
val -= decDigit*pwr;
// store the digit character
if(decDigit <= 9) {
newNum[D - 1 - p] = (char) ('0' + (int)decDigit);
}
else {
newNum[D - 1 - p] = (char) ('A' + (int)(decDigit - 10));
}
}
return new String(newNum);
}
}
The algorithm is correct. Take a closer look instead at the place where you convert the input value to a decimal system and in particular at the limitations of the data type you are using.
Resources that could be helpful:
primitive data types - double point in the list
Floating point arithmetic
Question concerning similar problem
JLS - 4.2.3. Floating-Point Types, Formats, and Values
Hope this points you to the right track.
import java.math.BigInteger;
import java.util.Scanner;
public class BaseConversion {
public static void main(String[] args) {
Scanner s = new Scanner(System.in);
String theValue;
String result;
String newNum;
int initialBase;
int finalBase;
String[] parts = args;
if (parts.length > 0) {
theValue = parts[0];
isValidInteger(theValue);
initialBase = Integer.parseInt(parts[1]);
finalBase= Integer.parseInt(parts[2]);
isValidBase(finalBase);
}
else {
System.out.println("Please enter a value: ");
theValue = s.nextLine();
isValidInteger(theValue);
System.out.println("Please enter original base: ");
initialBase = s.nextInt();
System.out.println("Please enter new base: ");
finalBase = s.nextInt();
isValidBase(finalBase);
}
// check it
// isValidInteger(theValue, finalBase);
s.close();
newNum = convertInteger(theValue, initialBase, finalBase);
System.out.println("new number: " + newNum);
}
public static void isValidBase(int finalBase) {
if (finalBase < 2 || finalBase > 36) {
System.out.println("Error: Base must be greater than or equal to 2 & less than or equal to 36");
System.exit(1);
}
}
public static void isValidInteger(String num) {
char chDigit;
num = num.toUpperCase();
for(int d = 0; d < num.length(); d++) {
chDigit = num.charAt(d);
if (!Character.isLetter(chDigit) && !Character.isDigit(chDigit)) {
//System.out.println(chDigit);
System.out.println("Error character is not a letter or number");
System.exit(1);
}
}
}
public static String convertInteger(String theValue, int initialBase, int finalBase) {
BigInteger bigInteger = new BigInteger(theValue,initialBase);
String value = bigInteger.toString(finalBase);
value = value.toUpperCase();
return value;
}
}
Here is the correct solution. The problem was with the data type not the algorithm. I hope this helps anyone dealing with the same type of problem.
as the title suggests I am writing a simple prog using methods, that converts the char input of a Roman Numeral between ("M", "D", "C", "L", "X", "V", "I") And then printing the decimal equivalent.
I have written the program but it converts the decimal (int) to Roman Numeral
When modifying the program to accepts char input only to ("M", "D", "C", "L", "X", "V", "I") then outputting decimal, I get errors since char cannot be converted to int.
Any suggestions on how I would change this. Thanks
import java.util.Scanner;
class RomanNumeral {
public static String romanNumeralToInt(int romanNumeral) {
String Numeral = "";
int repeat;
int value[] = {1000, 500, 100, 50, 10, 5, 1 };
String symbol[] = {"M", "D", "C", "L", "X", "V", "I" };
for(int x = 0; romanNumeral > 0; x++) {
repeat = romanNumeral / value[x];
for(int i = 1; i <= repeat; i++) {
Numeral = Numeral + symbol[x];
}
romanNumeral = romanNumeral % value[x];
}
return Numeral;
}
public static void main(String args[]){
Scanner input = new Scanner(System.in);
final String INVALID = "Invalid number, try again!";
final int VALIDATE_NUMBER_1 = 1;
final int VALIDATE_NUMBER_5 = 5;
final int VALIDATE_NUMBER_10 = 10;
final int VALIDATE_NUMBER_50 = 50;
final int VALIDATE_NUMBER_100 = 100;
final int VALIDATE_NUMBER_500 = 500;
final int VALIDATE_NUMBER_1000 = 1000;
while (true) {
System.out.print("Enter a number: ");
int inputValue = input.nextInt();
if (inputValue == VALIDATE_NUMBER_1) {
System.out.println(VALIDATE_NUMBER_1 + " = " + romanNumeralToInt(1));
}
else if (inputValue == VALIDATE_NUMBER_5) {
System.out.println(VALIDATE_NUMBER_5 + " = " + romanNumeralToInt(5));
}
else if (inputValue == VALIDATE_NUMBER_10) {
System.out.println(VALIDATE_NUMBER_10 + " = " + romanNumeralToInt(10));
}
else if (inputValue == VALIDATE_NUMBER_50) {
System.out.println(VALIDATE_NUMBER_50 + " = " + romanNumeralToInt(50));
}
else if (inputValue == VALIDATE_NUMBER_100) {
System.out.println(VALIDATE_NUMBER_100 + " = " + romanNumeralToInt(100));
}
else if (inputValue == VALIDATE_NUMBER_500) {
System.out.println(VALIDATE_NUMBER_500 + " = " + romanNumeralToInt(500));
}
else if (inputValue == VALIDATE_NUMBER_1000) {
System.out.println(VALIDATE_NUMBER_1000 + " = " + romanNumeralToInt(1000));
}
else {
System.out.println(INVALID);
}
}
}
}
UPDATE
Code modified as suggested from post, althought still has errors as String cannot be converted to Int. Any suggestions. Thank you
import java.util.Scanner;
class RomanTest {
public static int romanNumeralToInt(char romanNumeral) {
String Numeral = "";
int repeat;
int value[] = {1000, 500, 100, 50, 10, 5, 1 };
char symbol[] = {'M', 'D', 'C', 'L', 'X', 'V', 'I' };
for(char x = 0; romanNumeral > 0; x++) {
repeat = romanNumeral / value[x];
for(int i = 1; i <= repeat; i++) {
Numeral = Numeral + symbol[x];
}
romanNumeral = romanNumeral % value[x];
}
return Numeral;
}
public static void main(String args[]){
Scanner input = new Scanner(System.in);
final String INVALID = "Invalid number, try again!";
final char VALIDATE_CHAR_M = 'M';
final char VALIDATE_CHAR_D = 'D';
final char VALIDATE_CHAR_C = 'C';
final char VALIDATE_CHAR_L = 'L';
final char VALIDATE_CHAR_X = 'X';
final char VALIDATE_CHAR_V = 'V';
final char VALIDATE_CHAR_I = 'I';
while (true) {
System.out.print("Enter a number: ");
char inputValue = input.nextLine().charAt(0);
if (inputValue == VALIDATE_CHAR_M) {
System.out.println(VALIDATE_CHAR_M + " = " + romanNumeralToInt('M'));
}
else if (inputValue == VALIDATE_CHAR_D) {
System.out.println(VALIDATE_CHAR_D + " = " + romanNumeralToInt('D'));
}
else if (inputValue == VALIDATE_CHAR_C) {
System.out.println(VALIDATE_CHAR_C + " = " + romanNumeralToInt('C'));
}
else if (inputValue == VALIDATE_CHAR_L) {
System.out.println(VALIDATE_CHAR_L + " = " + romanNumeralToInt('L'));
}
else if (inputValue == VALIDATE_CHAR_X) {
System.out.println(VALIDATE_CHAR_X + " = " + romanNumeralToInt('X'));
}
else if (inputValue == VALIDATE_CHAR_V) {
System.out.println(VALIDATE_CHAR_V + " = " + romanNumeralToInt('V'));
}
else if (inputValue == VALIDATE_CHAR_I) {
System.out.println(VALIDATE_CHAR_I + " = " + romanNumeralToInt('I'));
}
else {
System.out.println(INVALID);
}
}
}
}
First of all you should pay attention public static int romanNumeralToInt(char romanNumeral) it should return int, but you are returning String Numeral = ""; - it's String, Java as C# is strongly typed language, so you have to return String.
Second: concatenating String in way you are doing
for(int i = 1; i <= repeat; i++) {
Numeral = Numeral + symbol[x];
}
is not recommended (too slow, String is immutable so on every concatenation you are creating new String). Better approach is to use StringBuilder.
I've modified your code and came with something like :
private String decimalToRoman(int number) {
String[] romans = {"M", "CM", "D", "C", "XC", "L", "X", "IX", "V", "I"};
int[] values = {1000, 900, 500, 100, 90, 50, 10, 9, 5, 1};
StringBuilder builder = new StringBuilder();
for (int i = 0; i < values.length; i++) {
int times= number / values[i];
if (times== 0) {
continue;
}
if (times == 4 && i > 0) {
builder.append(romans[i]);
builder.append(romans[i - 1]);
} else {
for (int ii = 0; ii < times; ii ++) {
builder.append(romans[i]);
}
}
number = number % values[i];
}
return builder.toString();
}
You are doing very things in the wrong way. Here is one way to do.
class RomanNumeral {
public static void romanNumeralToInt(String romanNumeral) {
Map<Character,Integer> mapping = new HashMap<>();
mapping.put('M',1000);
mapping.put('D',500);
mapping.put('C',100);
mapping.put('L',50);
mapping.put('X',10);
mapping.put('V',5);
mapping.put('I',1);
int result = 0;
for(char each : romanNumeral.toCharArray()){
if(mapping.containsKey(each)){
result += mapping.get(each);
}
else{
System.out.println("Invalid number");
return;
}
}
System.out.println(result);
}
public static void main(String args[]) {
Scanner input = new Scanner(System.in);
System.out.print("Enter a number: ");
String inputValue = input.nextLine();
romanNumeralToInt(inputValue);
}
}
The code in the main method already just accept the values 1000, 500, 100, 50, 10, 5, 1. Then in your romanNumeralToInt, there is some operations which are not necessary. Because you already have two arrays mapping for example 1 to I or 5 to V. If you find the index of 1 in the int array then your roman numeral is symbol[foundIndex]. I did not get the the purpose of those two for loops.
I get errors since char cannot be converted to int.
char can be converted to int. But "M" is not char, it is a String. 'M' is a char.
You can get a char from the user in the following way:
char charValue = input.nextLine().charAt(0);
So my goal this week was to find the hexadecimal octal and binary for decimal. I was able to get the hexdecimal, binary, and octal but were individual loops on different public class. So i was wondering how could i make this code one and read the hexadecimal, octal, and binary all in one loop.
decimal to hexadecimal
import java.util.Scanner;
public class uncode {
public static void main (String[] args) {
Scanner input = new Scanner(System.in);
System.out.println("Enter a decimal number: ");
int decimal = input.nextInt();
String hex = "";
while (decimal != 0 ) {
int hexValue = decimal % 16;
char hexDigit = (hexValue <= 9 && hexValue > 0) ?
(char) (hexValue + '0') : (char)(hexValue - 10 + 'A');
hex = hexDigit + hex;
decimal = decimal / 16;
}
System.out.println("The hex number is " + hex);
}
}
decimal to octal
import java.util.Scanner;
public class octal {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.println("Enter a decimal number: ");
int decimal = input.nextInt();
String octal = "";
while ( decimal > 0 ) {
int remainder = decimal % 8;
octal = remainder + octal;
decimal = decimal / 8;
}
System.out.println("Octal number: " + octal);
}
}
decimal to binary
import java.util.Scanner;
public class GuessNumbers {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.println("Enter a decimal number: ");
int decimal = input.nextInt();
String binary = "";
while (decimal > 0) {
int remainder = decimal % 2;
binary = remainder + binary;
decimal = decimal / 2;
}
System.out.println("Binary number: " + binary);
}
}
Easy way would be to use already present converstions, for example
Scanner input = new Scanner(System.in);
System.out.println("Enter a decimal number: ");
int decimal = input.nextInt();
String hex = Integer.toHexString(decimal);
String oct = Integer.toOctalString(decimal);
String bin = Integer.toBinaryString(decimal);
If you need an integer value, not the string, you can use
int h = Integer.parseInt(hex, 16);
int o = Integer.parseInt(oct, 8);
int b = Integer.parseInt(bin, 2);
Assuming you don't want to use these methods (let's say you have your reasons).
First, you need to put your code in a method, not inside main.
Then you can do something like this:
public class Class {
public static void uncode() {
Scanner input = new Scanner(System.in);
System.out.println("Enter a decimal number: ");
int decimal = input.nextInt();
String hex = "";
while (decimal != 0) {
int hexValue = decimal % 16;
char hexDigit = (hexValue <= 9 && hexValue > 0) ? (char) (hexValue + '0')
: (char) (hexValue - 10 + 'A');
hex = hexDigit + hex;
decimal = decimal / 16;
}
System.out.println("The hex number is " + hex);
}
public static void octal() {
Scanner input = new Scanner(System.in);
System.out.println("Enter a decimal number: ");
int decimal = input.nextInt();
String octal = "";
while (decimal > 0) {
int remainder = decimal % 8;
octal = remainder + octal;
decimal = decimal / 8;
}
System.out.println("Octal number: " + octal);
}
public static void GuessNumbers() {
Scanner input = new Scanner(System.in);
System.out.println("Enter a decimal number: ");
int decimal = input.nextInt();
String binary = "";
while (decimal > 0) {
int remainder = decimal % 2;
binary = remainder + binary;
decimal = decimal / 2;
}
System.out.println("Binary number: " + binary);
}
public static void allInOne() {
Scanner input = new Scanner(System.in);
System.out.println("Enter a decimal number: ");
int decimal = input.nextInt();
int hex = decimal;
int oct = decimal;
int bin = decimal;
String hexal = "";
String octal = "";
String binary = "";
while (hex > 0 || oct > 0 || bin > 0) {
if (hex > 0) {
// Get Hexal
int hexValue = hex % 16;
char hexDigit = (hexValue <= 9 && hexValue > 0) ? (char) (hexValue + '0')
: (char) (hexValue - 10 + 'A');
hexal = hexDigit + hexal;
hex = hex / 16;
}
if (oct > 0) {
// Get Octal
int remainder = oct % 8;
octal = remainder + octal;
oct = oct / 8;
}
if (bin > 0) {
// Get Binary
int remainder = bin % 2;
binary = remainder + binary;
bin = bin / 2;
}
}
System.out.println("The hex number is " + hexal);
System.out.println("Octal number: " + octal);
System.out.println("Binary number: " + binary);
}
public static void main(String[] args) {
uncode();
octal();
GuessNumbers();
allInOne();
}
}
I tried to make as little changes to your code as possible.
Here i convert from decimal to octal,bineary,hexadecimal by calling method getEveryFromDeci(param1,param2) where param1 - any decimal number and param2- its base value like 8,2,16.
And also i convert octal,bineary,hexadecimal to decimal by calling method allToDeci(param1,param2) where param1 - value of hexadecimal,bineary,octal in string form and param2- base value of hexadecimal
private String getEveryFromDeci(Integer x,Integer y){
List<String> al = deciBin(x,y,new ArrayList<String>());
StringBuffer buffer = new StringBuffer();
for(String s : al)
buffer.append(s);
return buffer.toString();
}
private List<String> deciBin(Integer a,Integer b,List<String> list){
if(a>=b){
deciBin(a/b,b,list);
list.add(a%b > 9 ? getHexaDecimal(a%b):Integer.toString(a%b));
}else
list.add(Integer.toString(a));
return list;
}
private String getHexaDecimal(int d){
String s= null;
switch(d){
case 10:
s="A";
break;
case 11:
s="B";
break;
case 12:
s="C";
break;
case 13:
s="D";
break;
case 14:
s="E";
break;
case 15:
s="F";
break;
}
return s;
}
private int allToDeci(String applyNum,int type){
int sum =0;
char[] ch = applyNum.toCharArray();
for(int pum=0;pum<ch.length;pum++)
sum += Character.isDigit(ch[pum]) ? getAct(ch.length-(pum+1),type) * Character.getNumericValue(ch[pum]) :getAct(ch.length-(pum+1),type) * getNum(ch[pum]);
return sum;
}
private int getNum(char ch){
int num = 0;
switch(ch){
case 'A':
num =10;
break;
case 'B':
num = 11;
break;
case 'C':
num =12;
break;
case 'D':
num =13;
break;
case 'E':
num =14;
break;
case 'F':
num=15;
break;
default:
num =Character.getNumericValue(ch);
break;
}
return num;
}
private int getAct(int k,int p){
int s=1;
if(k >0){
for(int i=0;i<k;i++)
s *=p;
return s;
}else
return 1;
}
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I have to write a Java program to convert Arabic numerals into Roman and vice versa, but I have troubles with my code,can anybody show me on this example how it should realy look,because i have got no idea how it shoud look like(
import java.util.*;
public class Du3 {
static int last = 2000;
static int numbers[] = {1, 4, 5, 9, 10, 50, 100, 500, 1000 };
static String letters[] = { "I", "IV", "V", "IX", "X", "L", "C", "D", "M"};
public static void main (String[] args){
System.out.println("Enter your Roman Numerals or Integer number:");
Scanner cti = new Scanner(System.in);
String a = cti.next();
char c = a.charAt( 0 );
char a1=convertRomanToInt(romanValue);
if ( Character.isDigit( c ) ){
System.out.println("Roman value = " + integerValue);}
else {
System.out.println("Integer value = " + romanValue);
}
static int convertRomanToInt(String romanNumeral){
int integerValue = 0;
for (int i = 0; i < romanNumeral.length(); i++){
char ch = romanNumeral.charAt( i );
int number = letterToNumber( ch );
if ( number == -1){
throw new NumberFormatException("Invalid format");
}
if (last<number)
number-=last- 1;
integerValue += number;
last = number;
}
return integerValue;
}
private static int letterToNumber(char letter){
switch (letter) {
case 'I': return 1;
case 'V': return 5;
case 'X': return 10;
case 'L': return 50;
case 'C': return 100;
case 'D': return 500;
case 'M': return 1000;
default: return -1;
}
}
static String convertIntegerToRoman(int number){
String romanValue = "";
int N = number;
while ( N > 0 ){
for (int i = 0; i < numbers.length; i++){
if ( N < numbers[i] ){
N -= numbers[i-1];
romanValue += letters[i-1];
break;
}
}
}
return romanValue;
}
}
Well, this is clearly wrong:
char a1=convertRomanToInt(romanValue);
The method convertRomanToInt() returns an int but you are assigning it to a1, which is a char.
Then you never do anything with a1, but you go on to try and print the variable integerValue:
if ( Character.isDigit( c ) ){
System.out.println("Roman value = " + integerValue);}
But integerValue is only declared inside the scope of the convertRomanToInt() method. It's not available in main().