hex conversion...
At line:
try{
if (ch<'0' || ch>'F')
throw new NumberFormatException("not
.
.
When ch is G, it doesn't throw "not a hex number." error?
Q1: 'G' > 'F', why then this doesn't work.
Q2: What happens if the data supplied is lower case? like g in place of G or b in place of B?
Thank you.
try{
if (ch<'0' || ch>'F')
throw new NumberFormatException("not
.
.
When ch is G, it doesn't throw "not a hex number." error?
Q1: 'G' > 'F', why then this doesn't work.
Q2: What happens if the data supplied is lower case? like g in place of G or b in place of B?
Thank you.
import java.util.Scanner;
public class Exercise13_6{
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.print("Enter a hex number: ");
String hex=input.nextLine();
System.out.println("The decimal value for hex number "
+ hex + " is " + hexToDecimal(hex.toUpperCase()));
}
public static int hexToDecimal(String hex) {
int decimalValue=0;
for(int i=0; i<hex.length();i++) {
char hexChar=hex.charAt(i);
decimalValue=decimalValue*16+hexToDecimal(hexChar);
}
return decimalValue;
}
public static int hexToDecimal(char ch) {
int temp=0;
try{
if (ch<'0' || ch>'F')
throw new NumberFormatException("not a hex number.");
if (ch>='A' && ch <='F')
temp = 10+ch-'A';
else
temp = ch-'0';
}catch (NumberFormatException ex){
// ex.printStackTrace();
}
return temp;
}
}
Last Comment
There is a method hex to int you don't need to write it
http://download.oracle.com/javase/6/docs/api/java/lang/Integer.html#valueOf%28java.lang.String,%20int%29
(Integere.valueOf(String, 16)).intVlaue()
That is becaiue you have additional catch loop there
public static int hexToDecimal(char ch) throws NumberFormatException {
int temp=0;
if (ch<'0' || ch>'F')
throw new NumberFormatException("not a hex number.");
if (ch>='A' && ch <='F')
temp = 10+ch-'A';
else
temp = ch-'0';
return temp;
}
You were catching it in the additional catch loop and even not printing the stackTrace - so uyou just caught the exception and
didn't inform anyoje about it - and you didn't see that it was throwing it - the above post should work
didn't inform anyoje about it - and you didn't see that it was throwing it - the above post should work
That's how it works:
public class TryHexToDecimal {
public static int hexToDecimal(char ch) throws NumberFormatException {
int temp=0;
if (ch<'0' || ch>'F')
throw new NumberFormatException("not a hex number.");
if (ch>='A' && ch <='F')
temp = 10+ch-'A';
else
temp = ch-'0';
return temp;
}
public static void main(String[] args) {
System.out.println(hexToDecimal('G'));
}
}
Exception in thread "main" java.lang.NumberFormatException: not a hex number.
at Miscellaneous.hexToDecimal(Miscellaneous.java:24)
at Miscellaneous.main(Miscellaneous.java:39)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:110)
lowercase is bigger than upper case
so
'a' > 'F'
so it will cause exception also
so you want to do something like that:
But then you should take care of another oart where uyou
should assign values to a-f lowere case
Instead of doing all that just use the method
which makes int out of hex string which I posted above
so
'a' > 'F'
so it will cause exception also
so you want to do something like that:
boolean good = false;
if((ch >= '0' && ch <= 'F') || (ch >= 'a' && ch <= 'f'))good = true;
if (!good)
throw new NumberFormatException("not a hex number.");
But then you should take care of another oart where uyou
should assign values to a-f lowere case
Instead of doing all that just use the method
which makes int out of hex string which I posted above
and maybe even better method:
http://download.oracle.com/javase/6/docs/api/java/lang/Integer.html#parseInt%28java.lang.String,%20int%29
int i = Integer.parseInt(String s, int radix)
This is how it parseInt() method works:
Output:
Output:
int inum = Integer.parseInt("12Fc10",16);
System.out.println("inum: " + inum);
Output:
inum: 1244176
int inum1 = Integer.parseInt("12Fc10g",16);
Output:
Exception in thread "main" java.lang.NumberFormatException: For input string: "12Fc10g"
at java.lang.NumberFormatException.forInputString(NumberFormatException.java:48)
at java.lang.Integer.parseInt(Integer.java:458)
at Miscellaneous.main(Miscellaneous.java:47)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:110)
ASKER
On the original issue, I am getting error message like:
Enter a hex number: k
Exception in thread "main" java.lang.NumberFormatExce
at Exercise13_6.hexToDecimal(
at Exercise13_6.hexToDecimal(
at Exercise13_6.main(Exercise
Java Result: 1
BUILD SUCCESSFUL (total time: 4 seconds)
Where I just want:
K is not a hex
Enter a hex number: k
Exception in thread "main" java.lang.NumberFormatExce
at Exercise13_6.hexToDecimal(
at Exercise13_6.hexToDecimal(
at Exercise13_6.main(Exercise
Java Result: 1
BUILD SUCCESSFUL (total time: 4 seconds)
Where I just want:
K is not a hex
import java.util.Scanner;
public class Exercise13_6{
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.print("Enter a hex number: ");
String hex=input.nextLine();
System.out.println("The decimal value for hex number "
+ hex + " is " + hexToDecimal(hex.toUpperCase()));
}
public static int hexToDecimal(String hex) {
int decimalValue=0;
for(int i=0; i<hex.length();i++) {
char hexChar=hex.charAt(i);
decimalValue=decimalValue*16+hexToDecimal(hexChar);
}
return decimalValue;
}
// public static int hexToDecimal(char ch) {
public static int hexToDecimal(char ch) throws NumberFormatException {
int temp=0;
if (ch<'0' || ch>'F')
throw new NumberFormatException(ch + " is not a hex number.");
if (ch>='A' && ch <='F')
temp = 10+ch-'A';
else
temp = ch-'0';
return temp;
}
}
You need to define your own custom Exception and
after you catcgh NumberFormat throw your Custom exception - look
at our previous exrcises where you were doing calculator
after you catcgh NumberFormat throw your Custom exception - look
at our previous exrcises where you were doing calculator
Or you can do it like that - catch it
but not print the exception with toString() or with ex.printStackTrace()
but rather print your own message:
but not print the exception with toString() or with ex.printStackTrace()
but rather print your own message:
public static int hexToDecimal(char ch) {
int temp=0;
try{
boolean good = false;
if((ch >= '0' && ch <= 'F') || (ch >= 'a' && ch <= 'f'))good = true;
if (!good)
throw new NumberFormatException("not a hex number.");
if (ch>='A' && ch <='F')
temp = 10+ch-'A';
else
temp = ch-'0';
} catch(Exception ex){
System.out.println("Not a hex");
}
return temp;
}
ASKER
Thanks I guess I can handle this.
Say, like that:
pubblic class HandlingExcept {
public static int hexToDecimal(char ch) {
int temp=0;
try{
boolean good = false;
if((ch >= '0' && ch <= 'F') || (ch >= 'a' && ch <= 'f'))good = true;
if (!good)
throw new NumberFormatException("not a hex number.");
if (ch>='A' && ch <='F')
temp = 10+ch-'A';
else
temp = ch-'0';
} catch(Exception ex){
System.out.println(ch + " is not a hex character");
}
return temp;
}
public static void main(String[] args) {
System.out.println(hexToDecimal('g'));
}
}
g is not a hex character
ASKER
I still need to read some of your last emails...
This is what I have so far, but it has one error:
This is what I have so far, but it has one error:
import java.util.Scanner;
public class Exercise13_6{
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.print("Enter a hex number: ");
String hex=input.nextLine();
System.out.println("The decimal value for hex number "
+ hex + " is " + hexToDecimal(hex.toUpperCase()));
}
public static int hexToDecimal(String hex) {
int decimalValue=0;
for(int i=0; i<hex.length();i++) {
char hexChar=hex.charAt(i);
decimalValue=decimalValue*16+hexToDecimal(hexChar);
}
return decimalValue;
}
public static int hexToDecimal(char ch) throws
InvalidDataException13_6, NumberFormatException {
int temp=0;
boolean good = false;
try{
if((ch >= '0' && ch <= 'F') ||
(ch >= 'a' && ch <= 'f'))good = true;
if (!good) //{
throw new InvalidDataException13_6(ch+" is not a hex number.");
// }else{
if (ch>='A' && ch <='F')
temp = 10+ch-'A';
else
temp = ch-'0';
// }
} catch(Exception ex){
// System.out.println("Not a hex");
throw new InvalidDataException13_6 (ch+" is not a hex number.");
}
return temp;
}
}
class InvalidDataException13_6 extends Exception {
private String mistake;
public InvalidDataException13_6(String err)
{
super(err); // call super class constructor
mistake = err; // save message
}
public String toString(){
return mistake;
}
}
ASKER
I guess I have it now
import java.util.Scanner;
public class Exercise13_6{
public static void main(String[] args) throws
InvalidDataException13_6, NumberFormatException {
Scanner input = new Scanner(System.in);
System.out.print("Enter a hex number: ");
String hex=input.nextLine();
System.out.println("The decimal value for hex number "
+ hex + " is " + hexToDecimal(hex.toUpperCase()));
}
public static int hexToDecimal(String hex) throws
InvalidDataException13_6, NumberFormatException {
int decimalValue=0;
for(int i=0; i<hex.length();i++) {
char hexChar=hex.charAt(i);
decimalValue=decimalValue*16+hexToDecimal(hexChar);
}
return decimalValue;
}
public static int hexToDecimal(char ch) throws
InvalidDataException13_6, NumberFormatException {
int temp=0;
try{
if((ch >= '0' && ch <= 'F') || (ch >= 'a' && ch <= 'f'))//good = true;
throw new InvalidDataException13_6(ch+" is not a hex number.");
if (ch>='A' && ch <='F')
temp = 10+ch-'A';
else
temp = ch-'0';
} catch(Exception ex){
throw new InvalidDataException13_6 (ch+" is not a hex number.");
}
return temp;
}
}
class InvalidDataException13_6 extends Exception {
private String mistake;
public InvalidDataException13_6(String err)
{
super(err); // call super class constructor
mistake = err; // save message
}
public String toString(){
return mistake;
}
}
ASKER
not quite there yet.
Seems OK, but I'm not sure if it will be lower case, this part will work correctly:
if (ch>='A' && ch <='F')
temp = 10+ch-'A';
else
temp = ch-'0';
and if ch = 'b' - ?
if (ch>='A' && ch <='F')
temp = 10+ch-'A';
else
temp = ch-'0';
and if ch = 'b' - ?
>>
if (((ch >= '0') && (ch <= 'F')) || ((ch >= 'a') && (ch <= 'f'))) { //good = true;
throw new InvalidDataException13_6(c
" is not a hex number.");
}
>>
Your logic is the wrong way around there
if (((ch >= '0') && (ch <= 'F')) || ((ch >= 'a') && (ch <= 'f'))) { //good = true;
throw new InvalidDataException13_6(c
" is not a hex number.");
}
>>
Your logic is the wrong way around there
ASKER
I ran for k, this is whay I got:
run:
Enter a hex number: k
The decimal value for hex number k is 27
BUILD SUCCESSFUL (total time: 5 seconds)
which is wrong result. and:
Enter a hex number: A22
Exception in thread "main" A is not a hex number.
at Exercise13_6.hexToDecimal(
at Exercise13_6.hexToDecimal(
at Exercise13_6.main(Exercise
Java Result: 1
BUILD SUCCESSFUL (total time: 7 seconds)
run:
Enter a hex number: k
The decimal value for hex number k is 27
BUILD SUCCESSFUL (total time: 5 seconds)
which is wrong result. and:
Enter a hex number: A22
Exception in thread "main" A is not a hex number.
at Exercise13_6.hexToDecimal(
at Exercise13_6.hexToDecimal(
at Exercise13_6.main(Exercise
Java Result: 1
BUILD SUCCESSFUL (total time: 7 seconds)
ASKER
re:> Your logic is the wrong way around there
I will revise and test it again
I will revise and test it again
Use this logic :
but rervise the part where you calculate the actuall value form lower case - it should be sdifferent
boolean good = false;
if((ch >= '0' && ch <= 'F') || (ch >= 'a' && ch <= 'f'))good = true;
if (!good)
throw new NumberFormatException("not a hex number.");
but rervise the part where you calculate the actuall value form lower case - it should be sdifferent
ASKER
OK
I think this should work:
public static int hexToDecimal(char ch) {
int temp=0;
try{
boolean good = false;
if((ch >= '0' && ch <= 'F') || (ch >= 'a' && ch <= 'f'))good = true;
if (!good)
throw new NumberFormatException("not a hex number.");
if (Character.toUpperCase(ch)>='A' && Character.toUpperCase(ch)<='F')
temp = 10+Character.toUpperCase(ch)-'A';
else
temp = Character.toUpperCase(ch)-'0';
} catch(Exception ex){
System.out.println(ch + " is not a hex character");
}
return temp;
}
Or just convert your character to upper case form the very nebgging and that will make your code
mauch easier (baseically like it was in the beginning)
mauch easier (baseically like it was in the beginning)
>> if((ch >= '0' && ch <= 'F') || (ch >= 'a' && ch <= 'f'))good = true;
Won't work unfortunately - it will set good to true for '@'
You'd be better off with
Won't work unfortunately - it will set good to true for '@'
You'd be better off with
ch = Character.toLowerCase(ch);
good = "0123456789abcdef".indexOf(ch) > -1;
ASKER CERTIFIED SOLUTION
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>>if (Character.toUpperCase(ch)
Don't do that. Convert it straight away and call the method once, not multiple times
Don't do that. Convert it straight away and call the method once, not multiple times
Well, in the end use, parseInt as I mentioned above - this is definitely something wahich you sdon't want to write yourself
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>>this is definitely something wahich you sdon't want to write yourself
Well i think that goes without saying, outside an academic exercise, which is what i assume this is
Well i think that goes without saying, outside an academic exercise, which is what i assume this is
>>I think this should also work:
It doesn't - for the reason i gave at http:#:36945129
Can you tell me why you accepted an incorrect answer eghtebas?
It doesn't - for the reason i gave at http:#:36945129
Can you tell me why you accepted an incorrect answer eghtebas?
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This works for me:
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