help with arrays program in java

[Jr Winston]

Hi all. I have to write a java program that allows a user to enter an octal digit and output the binary equivalent for as many numbers as the person wishes using a direct access method.

The error is that even though it compiles, it loops the binary equivalent. The code goes as follows:


import java.util.Scanner; // initialize scanner class for input
public class Arrays
{
public static void main(String[] args)
{
int num = 0;
String OctalNum;
// declare array to hold 7 octal numbers and convert to binary numbers
int i;
int j;
int n;

char c; //to hold each number of input octal

char repeat; //to hold yes or no

//for numbers 1 to 7, make a binary equivalent

String binaryArray[]={"000", "001", "010", "011", "100", "101", "110", "111"};


do
{


Scanner input = new Scanner(System.in);
System.out.println("Octal to Binary Conversion");

System.out.println("Enter the Octal Number: ");
OctalNum = input.nextLine();


// make a loop to read as many numbers as the input octal has
for (i=0; i < OctalNum.length(); i++)
{
//read string by character then convert to an integer

c = OctalNum.charAt(0);

for (j=1; j < c; j++)
{
//convert character to integer (ex: "1" to 1)
n = Character.getNumericValue(c);
if(n <8)
{
binaryArray[0] = "000";
binaryArray[1] = "001";
binaryArray[2] = "010";
binaryArray[3] = "011";
binaryArray[4] = "100";
binaryArray[5] = "101";
binaryArray[7] = "111";

System.out.println(OctalNum+ " converted to binary is "+ binaryArray[n]);

// System.out.println();

}//end if
else if(n>7)
System.out.println( "Not a valid octal number!");

}

}

// prompt for input more OctalNum
System.out.print("Do you want to enter another Octal number? ");

System.out.println("Y for yes or N for No: ");
System.out.println();

String str= input.next(); //Read next char
repeat= str.charAt(0); //Get the first char

}
while(repeat=='Y' || repeat=='y');

}
}

[James E Baker]

Hi Jr....

First... to save you some grief when posting, make sure to use "code" button when posting code on the forum to make it easier to read and reply to.

I'm not 100% sure I know exactly how you want your output to look, but I have four suggestions for you to try.

1. At the beginning, you have the line "int num = 0;" for no apparent reason. It is never used in your code.
2. You have a line "c = OctalNum.charAt(0); " which I think you should change to "c = OctalNum.charAt(i); "
3. What is the "for (j=1; j < c; j++) " about? I would completely delete that from your code. It doesn't seem to serve a purpose and "c" is a char value not an int.
4. Change your output to "System.out.println(n+ " converted to binary is "+ binaryArray[n]); "

Below shows the changes I made....

import java.util.Scanner; // initialize scanner class for input 
public class Arrays 
{ 
public static void main(String[] args) 
{ 
// int num = 0;   // no reason for this?
String OctalNum; 
// declare array to hold 7 octal numbers and convert to binary numbers 
int i; 
int j; 
int n; 

char c; //to hold each number of input octal 

char repeat; //to hold yes or no 

//for numbers 1 to 7, make a binary equivalent 

String binaryArray[]={"000", "001", "010", "011", "100", "101", "110", "111"}; 


do 
{ 


Scanner input = new Scanner(System.in); 
System.out.println("Octal to Binary Conversion"); 

System.out.println("Enter the Octal Number: "); 
OctalNum = input.nextLine(); 


// make a loop to read as many numbers as the input octal has 
for (i=0; i < OctalNum.length(); i++) 
{ 
//read string by character then convert to an integer 

c = OctalNum.charAt(i); // changed 0 to i

//for (j=1; j < c; j++)   // no reason for this?
//{ 
//convert character to integer (ex: "1" to 1) 
n = Character.getNumericValue(c); 
if(n <8) 
{ 
binaryArray[0] = "000"; 
binaryArray[1] = "001"; 
binaryArray[2] = "010"; 
binaryArray[3] = "011"; 
binaryArray[4] = "100"; 
binaryArray[5] = "101"; 
binaryArray[7] = "111"; 

System.out.println(n+ " converted to binary is "+ binaryArray[n]); 

// System.out.println(); 

}//end if 
else if(n>7) 
System.out.println( "Not a valid octal number!"); 

} 

//} 

// prompt for input more OctalNum 
System.out.print("Do you want to enter another Octal number? "); 

System.out.println("Y for yes or N for No: "); 
System.out.println(); 

String str= input.next(); //Read next char 
repeat= str.charAt(0); //Get the first char 

} 
while(repeat=='Y' || repeat=='y'); 

} 
} 

My output is....

Octal to Binary Conversion
Enter the Octal Number:
0123
0 converted to binary is 000
1 converted to binary is 001
2 converted to binary is 010
3 converted to binary is 011
Do you want to enter another Octal number? Y for yes or N for No:

[Jr Winston]

thanks! i understand it now.