Thread: Reversing a String with no Buffer

i was wondering if anybody can give me some help with drawing out the logic behind reversing a string with the following results: sample = "My name is jack"; the reverse should display "yM eman si kcaj".... i know how to reverse the entire string but in this case how would i reverse the letters but keep the words in their same position???

Please don't double post questions. Your duplicate has been closed.

As for your problem, how would you do this logically? What are the individual steps necessary to achieve this on paper if you had a lot of words to go through? Now try to translate this logic into pseudo-code, and then code. Then if you get stuck at one step, please ask away.

didnt know it duplicated my connection got lost as soon as i hit post.... would i need a variable to specify the white space and another string variable for the new result??? also would it make a difference if i assigned the sample to a char array variable or can i just use String?

without using a StringBuffer object....

So you could just use a String and concatenate your building String to it. You need to parse your original String into words, and then work on each word. I'm thinking that I would write methods for both steps.

ok i thought there would be a faster way using simple for loops and maybe an if statement.... so i should make a method to separate the string of words into let's say, a String array and then another method to reverse each String element and return the result???

ok i read something about a char array but wasnt sure of its importance... so turn the input into a char array and then make a method that returns a string? how would i turn the char array into separate words?? by making the method return a String array???

I beg to differ. While Strings are immutable, a String variable can easily be reassigned a new reference. The easiest way to solve this is with simple String concatenation.

get String to be reveresed
split String via the split(...) method into an array of words.
create empty result String
for loop, looping over the array
   concatenate to the result String the reverse of the next word in array. Call a method to get the reverse word.
end for loop

call a method to reverse the current element in the array and then something like empty += revStr[x];
thanks for that nugget i think that's what i needed to write this

--- Update ---

wow i definitely wasnt thinking that much i had another plan n mind with more methods than two... thanks for the pseudo both of u

how would i swap char elements??? i have a code but where do i go from here

/*
 * Reverse a string but keep the words in their original positions
 */
 
import javax.swing.*;
 
class ReverseString {
 
    String inputStr;
    char[] charArray;
 
    public static void main(String[] args) {
        ReverseString revStr = new ReverseString();
        revStr.reverseSentence();
    }
 
    private void reverseSentence(){
 
        inputStr = JOptionPane.showInputDialog(null, "Enter a sentence:");
 
        charArray = inputStr.toCharArray();
 
        char beginIndex = charArray[0];
        char whiteSpace = ' ';
 
        for(int i = 1; i < charArray.length; i++){
            if(charArray[i] == whiteSpace){
                reverseSubstring(charArray, beginIndex, charArray[i]);
                beginIndex = charArray[i + 1];
            }
        }
    }
 
    private void reverseSubstring(char[] array, char startIndex, char endIndex){
        for(int i = startIndex; i < endIndex; i++){
            int temp;
 
        }
    }
}

so i would add another method to do the swap or should i just go ahead and keep coding in the for loop???

would i use an int as the temp variable even tho im swapping char elements??? it says the precision might be lost if i use char

it's still a little buggy

/*
 * Reverse a string but keep the words in their original positions
 */
 
import javax.swing.*;
 
class ReverseString {
 
    String inputStr;
    char[] charArray;
 
    public static void main(String[] args) {
        ReverseString revStr = new ReverseString();
        revStr.reverseSentence();
    }
 
    private void reverseSentence(){
 
        inputStr = JOptionPane.showInputDialog(null, "Enter a sentence:");
 
        charArray = inputStr.toCharArray();
 
        char beginIndex = charArray[0];
        char whiteSpace = ' ';
 
        for(int i = 0; i < charArray.length; i++){
            if(charArray[i] == whiteSpace){
                reverseSubstring(charArray, beginIndex, charArray[i]);
                beginIndex = charArray[i + 1];
            }
            System.out.print(charArray[i]);
        }
    }
 
    private void reverseSubstring(char[] array, char startIndex, char endIndex){
        for(int i = startIndex; i < endIndex; i++){
            int temp;
            temp = array[startIndex];
            array[startIndex] = array[endIndex];
            array[endIndex] = (char) temp;
        }
    }
}