Programming Forums > Application Development > Java

gam3r · Nov 8th, 2007, 6:16 AM

I'm trying to code a program in java which converts decimal to binary but i keep getting this error upon compile:

Quote:

Q1.java:11: 'class' or 'interface' expected
public static void main(String args[])

My code is

Quote:

import java.util.Scanner; //this program uses class scanner

public class Q1
{
public static int binTodec(String b)
{
System.out.println(Integer.toBinaryString(b));
}
}

public static void main(String args[])
{
Scanner input = new Scanner(System.in);
System.out.println("Please enter the decimal number you want to convert to binary");

String b = input.nextLine();

binToDec(b);

}

Can anyone help?

Thanks

Grich · Nov 8th, 2007, 6:40 AM

Change your to this and try it out.

(Toggle Plain Text)

import java.util.Scanner; //this program uses class scanner

public class Q1
{
public static String binToDec(int b)
{
return Integer.toBinaryString(b);
}


public static void main(String args[])
{
Scanner input = new Scanner(System.in);
System.out.println("Please enter the decimal number you want to convert to binary");

int b = input.nextInt();

System.out.println(binToDec(b));

} 
}

Remember, your "public static int binToDec" is setting a value, returning a value and you have to return a string when dealing with the "toBinaryString" function so I changed it to "public static String binToDec". You were setting a procedure. A bracket was in the wrong place as well.
Don't worry I'm not telling you off, just giving a few pointers.

Grich · Nov 8th, 2007, 6:42 AM

Also, your scanner had to be nextInt to get an integer from the user. You had a string wanting to be an integer and then a string a again.

gam3r · Nov 8th, 2007, 6:47 AM

Thanks for the tips. It works!

If i wanted to go about making this a recursive solution, how would i do it?

Grich · Nov 8th, 2007, 7:04 AM

You would have to make a class of it. For example:

(Toggle Plain Text)

public class Binary
{
public static String binToDec(int b)
{
return Integer.toBinaryString(b);
}
}

Just import it and use it. Classes are very in depth, wikipedia has some good articles on the topic.

Grich · Nov 8th, 2007, 7:12 AM

Sorry, I can't go into too much detail, too sleepy...

gam3r · Nov 8th, 2007, 8:01 AM

This is what i have done so far...not working of course

Quote:

public class exercise {

public static String decTobin (int n){
int r;
if (n>0){
r=n%2;
decTobin(r);

}
}
//public static int binTodec (String b){

// }
public static void main(String[] args) {

int d = Integer.parseInt(args[0]);
System.out.println("The binary representation of " + d + " is " + decTobin(d));
String b = args[1];
System.out.println("The decimal representation of " + b + " is " + binTodec(b));
}
}

i get a compile error missing return statment line 9

ReggaetonKing · Nov 8th, 2007, 9:08 AM

You should use the return statement to return a string value from your method.

Let me know if this works. I didn't compile or test this code.

(Toggle Plain Text)

public static String decToBin(int decimal, String str)
{
	str += decimal % 2;
	decimal /= 2;
	if (decimal == 0) 
		return new StringBuffer(str).reverse().toString();
	else 
		return decToBin(decimal, str);
}

gam3r · Nov 8th, 2007, 10:01 AM

Hey! Thanks for the reply. I tried using your code but it won't compile...just get "else without if on line9"..

The way you have done it isn't recursive though is it? i know my coding is horribly wrong for the conversion..

ReggaetonKing · Nov 8th, 2007, 10:05 AM

Quote:

Originally Posted by gam3r

Hey! Thanks for the reply. I tried using your code but it won't compile...just get "else without if on line9"..

The way you have done it isn't recursive though is it?

If you ask that question, you don't know what recursion is.

As you can see from my snippet of code, I did indeed have an if statement. How did you insert my code in yours? Please just don't copy and paste. Understand and learn from what others are writing. It is frustating to hold your hand every step of the way.

Nov 8th, 2007, 6:40 AM	#2
Grich Hobbyist Programmer Join Date: Sep 2007 Location: Sydney - Australia Posts: 204 Rep Power: 2	Re: Decimal to binary help Change your to this and try it out. (Toggle Plain Text) import java.util.Scanner; //this program uses class scanner public class Q1 { public static String binToDec(int b) { return Integer.toBinaryString(b); } public static void main(String args[]) { Scanner input = new Scanner(System.in); System.out.println("Please enter the decimal number you want to convert to binary"); int b = input.nextInt(); System.out.println(binToDec(b)); } } import java.util.Scanner; //this program uses class scanner public class Q1 { public static String binToDec(int b) { return Integer.toBinaryString(b); } public static void main(String args[]) { Scanner input = new Scanner(System.in); System.out.println("Please enter the decimal number you want to convert to binary"); int b = input.nextInt(); System.out.println(binToDec(b)); } } Remember, your "public static int binToDec" is setting a value, returning a value and you have to return a string when dealing with the "toBinaryString" function so I changed it to "public static String binToDec". You were setting a procedure. A bracket was in the wrong place as well. Don't worry I'm not telling you off, just giving a few pointers. __________________ SYNTAX ERROR ...

Nov 8th, 2007, 6:42 AM	#3
Grich Hobbyist Programmer Join Date: Sep 2007 Location: Sydney - Australia Posts: 204 Rep Power: 2	Re: Decimal to binary help Also, your scanner had to be nextInt to get an integer from the user. You had a string wanting to be an integer and then a string a again. __________________ SYNTAX ERROR ...

Nov 8th, 2007, 6:47 AM	#4
gam3r Newbie Join Date: Jun 2005 Location: London, England Posts: 24 Rep Power: 0	Re: Decimal to binary help Thanks for the tips. It works! If i wanted to go about making this a recursive solution, how would i do it? __________________ biggest NOOB ever :P

Nov 8th, 2007, 7:04 AM	#5
Grich Hobbyist Programmer Join Date: Sep 2007 Location: Sydney - Australia Posts: 204 Rep Power: 2	Re: Decimal to binary help You would have to make a class of it. For example: (Toggle Plain Text) public class Binary { public static String binToDec(int b) { return Integer.toBinaryString(b); } } public class Binary { public static String binToDec(int b) { return Integer.toBinaryString(b); } } Just import it and use it. Classes are very in depth, wikipedia has some good articles on the topic. __________________ SYNTAX ERROR ...

Nov 8th, 2007, 7:12 AM	#6
Grich Hobbyist Programmer Join Date: Sep 2007 Location: Sydney - Australia Posts: 204 Rep Power: 2	Re: Decimal to binary help Sorry, I can't go into too much detail, too sleepy... __________________ SYNTAX ERROR ...

Nov 8th, 2007, 9:08 AM	#8
ReggaetonKing Sexy Programmer Join Date: Nov 2005 Location: New Jersey Posts: 891 Rep Power: 3	Re: Decimal to binary help You should use the return statement to return a string value from your method. Let me know if this works. I didn't compile or test this code. (Toggle Plain Text) public static String decToBin(int decimal, String str) { str += decimal % 2; decimal /= 2; if (decimal == 0) return new StringBuffer(str).reverse().toString(); else return decToBin(decimal, str); } public static String decToBin(int decimal, String str) { str += decimal % 2; decimal /= 2; if (decimal == 0) return new StringBuffer(str).reverse().toString(); else return decToBin(decimal, str); } __________________ I would love to change the world, but they won't give me the source code!

Nov 8th, 2007, 10:01 AM	#9
gam3r Newbie Join Date: Jun 2005 Location: London, England Posts: 24 Rep Power: 0	Re: Decimal to binary help Hey! Thanks for the reply. I tried using your code but it won't compile...just get "else without if on line9".. The way you have done it isn't recursive though is it? i know my coding is horribly wrong for the conversion.. __________________ biggest NOOB ever :P

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Programming Forums > Application Development > Java

Decimal to binary help