Bit Strings in Java

Hello.
I was writing a java code for class and I was unable to figure out how strings and sub-strings work. Can anyone provide some insight on the program.
Here is the problem: Given a bit string expression, such as 10110 OR 11101, evaluate it.
Input: Each string represents a bit-string expression with one operator in it. The operators are AND, OR, and NOT. The operands are bit strings, from 1 to 8 bit long. If the expression contains two operands, they will be the same length. Each input must read as a single string. A single blank will separate the operators and operands.
Output: the value of the expression.
My code so far...

Code :

---

import java.util.Scanner;
import java.io.File;
import java.io.IOException;
 
public class BitStringsClient 
{
	public static void main(String[] args) throws IOException
	{
		//communicating with the data
		Scanner inFile = new Scanner(new File("BitStrings.txt"));
 
		//declare variables
		String firststr, secondstr = null;
		int charValue = 0;
 
		//process data
		while(inFile.hasNext())
		{
			firststr = inFile.next();
			if(firststr.equals("NOT"));
			{
				secondstr = inFile.nextLine();
				//for loop to convert bits to their opposite
				for(int index = 0; index < firststr.length(); index++)
				{
					if()
				}
			}
			//else
			if(firststr.equals("AND"));
			{
				secondstr = inFile.nextLine();
				//for loop to multiply strings
				for(int index = 0; index < firststr.length(); index++)
					{
 
					}
			}
			//else
			if(firststr.equals("OR"));
			{
				secondstr = inFile.nextLine();
				//for loop to add strings
				for(int index = 0; index < firststr.length(); index++)
					{
 
					}
			}
			//else
 
		}
 
	}
}

---

Can you explain your problem? Does the code compile? If not post the errors.
Does the code execute?
Post the output and explain what is wrong with it and show what it should be.

To make testing easier, I suggest that you replace the file with a String. For example:
Scanner inFile = new Scanner("1101 AND 1000");

Then we'll all have the same data for testing when there is a problem.


One way to get to each character in a String is to use the charAt() method. Get one char from each String and do the operation on them and place the output value in a third String.

For debugging I'd print out the values of every String that is read to be sure it is what you expected to read.

First, my teacher wants us to use a text file for the assignment.
My data:
Input:
101 OR 011
101 AND 011
NOT 1100111
The problem is I don't know what to put exactly in the final "if' statements.
I know what you are saying is what I have to do in terms of your suggestion. I just dont know how because I missed the notes on it in class. Please futher explain.

For testing you can put the data in the program. When you have the logic of the program working,
then you can add the code to read from a file.

You need to write a small test program that takes a String and prints out the characters in the String one by one in a loop. There are a couple of ways to get a single character. One is the charAt() method. Another is substring.
Write a small test program that uses one or both of these methods in a loop for the length of the String to get the String's characters one by one and print them out.

Cross posted at Bit Strings in Java - Java | DaniWeb

Well, I did do your suggestions. Now what? how do i perform the operation itself?

Apply the bitwise operator to the "bits" from each String.
Do you know the rules for each operator? Given two bits (one from each String) and an operator, what is the result? It will be either a '0' or a '1'.

Code :

---

					newstr = secondstr.substring(index, (index + 1));
					System.out.print(newstr);

---

Where would the operator go? Have I done this correctly so far?

Please explain what you are trying to do in the code you posted.
What are the steps the program must take to do the task? Write a list of short,simple steps.
For example, the first step could be:
read a String with the expression to evaluate.
Then what???

I'm just trying to get the individual numbers out.

Quote:

---

trying to get the individual numbers out.

---

Post an example of the String you are working on and what you are trying to get.

Did you try what I suggested in post#4?
Post the program you wrote and its output when you execute it.

input: 1100111
current output : 1100111
desired output: 0011000

Code :

---

import java.util.Scanner;
import java.io.File;
import java.io.IOException;
 
public class BitStringsClient 
{
	public static void main(String[] args) throws IOException
	{
		//communicating with the data
		Scanner inFile = new Scanner("NOT 1100111");
 
		//declare variables
		String firststr, secondstr;
		String newstr;
 
		//process data
		while(inFile.hasNext())
		{
			firststr = inFile.next();
			if(firststr.equals("NOT"));
			{
				secondstr = inFile.nextLine();
				//for loop to convert bits to their opposite
				for(int index = 0; index < secondstr.length(); index++)
				{	
					newstr = secondstr.substring(index, (index + 1));
					System.out.print(newstr);
				}
 
			}
			//else
			/*if(firststr.equals("AND"));
			{
				secondstr = inFile.nextLine();
				//for loop to multiply strings
				for(int index = 0; index < firststr.length(); index++)
					{
 
					}
			}
			//else
			if(firststr.equals("OR"));
			{
				secondstr = inFile.nextLine();
				//for loop to add strings
				for(int index = 0; index < firststr.length(); index++)
					{
 
					}
			}*/
 
		}
 
	}
}

---

You did not post the full contents of the expression you are trying to evaluate. (the NOT is missing)

Where do you do the NOT logic on the value the code reads into the newstr variable? The code just echos back what was read in.

that is exactly what i dont know how to do.

First you need to know what the NOT operator does. And the AND and the OR
You should find a tutorial that describes how those boolean operators work.

i know what they do, i just dont know how to apply them here

Quote:

---

how to apply them here

---

Your input consists of binary digits: 0 or 1
Given a binary digit what is its NOT value?
Show the two examples.

While the site was down, i figured out the not part.

Code :

---

					charValue = secondstr.charAt(index);
			http://www.javaprogrammingforums.com/newreply.php?do=postreply&t=13796		if(charValue != '0')
						notValue = 0;
					if(charValue != '1')
						notValue = 1;
					System.out.print(notValue);

---

input: NOT 1100111
Output: 0011000
SO, that part is fine.

On to the next one.