1+ package com .java .convertor ;
2+ 3+ /*
4+ * Hexadecimal To Decimal Conversion
5+ * -------------------------------
6+ *
7+ * Hexadecimal::
8+ * In mathematics and computing, the hexadecimal
9+ * (also base 16 or hex) numeral system is a
10+ * positional numeral system that represents numbers
11+ * using a radix (base) of 16.
12+ *
13+ * Unlike the common way of representing numbers
14+ * using 10 symbols, hexadecimal uses 16 distinct symbols,
15+ * most often the symbols "0"–"9" to represent
16+ * values 0 to 9, and "A"–"F" (or alternatively "a"–"f")
17+ * to represent values 10 to 15.
18+ *
19+ * Steps
20+ * -----
21+ * - get input (hexadecimal) from the user
22+ * - create a variable, lets say pow (default value is 0)
23+ * - create a variable, lets say decimal (default value is 0)
24+ * - get the last digit of the hex number
25+ * - get the corresponding numeric value
26+ * - because hexadecimal digits contains alphabets also
27+ * {0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F}
28+ * - multiply the numeric value with power of 16 to pow variable
29+ * - add the above result with
30+ * - increment the pow variable
31+ * - continue all the above steps for all the digits of hex
32+ * - read the digits from the reverse direction
33+ *
34+ * say hex = 153
35+ * decimal = 1 * 16^2 + 5 * 16^1 + 3 * 16^0
36+ * decimal = 1 * 256 + 5 * 16 + 3 * 1
37+ * decimal = 256 + 80 + 3
38+ * decimal = 339
39+ *
40+ * say hex = FAD
41+ * decimal = F * 16^2 + A * 16^1 + D * 16^0
42+ * decimal = 15*256 + 10*16 + 13*1
43+ * decimal = 3840 + 160 + 13
44+ * decimal = 4013
45+ */
46+ 47+ public class HexaToDecimal {
48+ public static void main (String [] args ) {
49+ String hex = "35432" ;
50+ // String hex = "153";
51+ // String hex = "A0";
52+ // String hex = "FAD";
53+ 54+ int decimal = 0 ;
55+ int pow = 0 ;
56+ 57+ for (int i =hex .length ()-1 ;i >=0 ;i --){
58+ char unitChar = hex .charAt (i );
59+ int unitDigitValue = numericValue (unitChar );
60+ decimal = (int ) (decimal + unitDigitValue *Math .pow (16 , pow ));
61+ pow ++;
62+ }
63+ 64+ System .out .println ("Hexadecimal Value is :" +hex );
65+ System .out .println ("Decimal Value :" +decimal );
66+ }
67+ 68+ private static int numericValue (char c ){
69+ //hexa digit may contain alphabet also
70+ //so we need to it to the corresponding numeric value
71+ switch (c ) {
72+ case '0' :
73+ return 0 ;
74+ case '1' :
75+ return 1 ;
76+ case '2' :
77+ return 2 ;
78+ case '3' :
79+ return 3 ;
80+ case '4' :
81+ return 4 ;
82+ case '5' :
83+ return 5 ;
84+ case '6' :
85+ return 6 ;
86+ case '7' :
87+ return 7 ;
88+ case '8' :
89+ return 8 ;
90+ case '9' :
91+ return 9 ;
92+ case 'a' :
93+ case 'A' :
94+ return 10 ;
95+ case 'b' :
96+ case 'B' :
97+ return 11 ;
98+ case 'c' :
99+ case 'C' :
100+ return 12 ;
101+ case 'd' :
102+ case 'D' :
103+ return 13 ;
104+ case 'e' :
105+ case 'E' :
106+ return 14 ;
107+ case 'f' :
108+ case 'F' :
109+ return 15 ;
110+ default :
111+ return 0 ;
112+ }
113+ }
114+ }
115+ /*
116+ OUTPUT
117+ Hexadecimal Value is :35432
118+ Decimal Value :218162
119+
120+ Hexadecimal Value is :A0
121+ Decimal Value :160
122+
123+ Hexadecimal Value is :153
124+ Decimal Value :339
125+
126+ Hexadecimal Value is :FAD
127+ Decimal Value :4013
128+ */
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