Help with a simple java program

Hey guys please help me out. This is homework by the way so please don't spoon feed me code but instead give me some advice on what to do. My goal is to make a program that lets the user change a word in a string. First it prompts the user to enter a string then prompts what word to look for then prompts another for what word you want to use to replace the word you looked for.
This is what I have so far.

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Code:

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mport java.util.Scanner;
public class replacement {


                int pos = 0;
               
                int lengther = 0;
               
                String replacer = new String(); // placeholder for the string that is replacing another string
               
                String replacee = new String();
               
                String line1 = new String();
               
                String line2 = new String();
       
                Scanner checker = new Scanner(System.in); // new object
               
                System.out.print("Enter your sentence: ");
                line1 = checker.nextLine();
               
                System.out.print("What word do you want to look for?: "); // asks what word you want to scan
                replacee = checker.nextLine();
               
                System.out.print("What word do you want to use?: "); // asks what word do you want to use to replace the word you looked for
                replacer = checker.nextLine();
               

                while (pos >=0){ // stops at neg 1
                        pos = line1.indexOf(replacee); // gets position of word the user is looking for
                       
                        if (pos >=0){ // start if
                                line2 = line1.substring(0,pos);
                               
                                line2 = line2 + replacer;
                               
                               
                               
                               
                               
                        }// end if
                       
       
                       
                       
                       
                }// end loop
               
               
               
               
               
               
       
               
               
               
               
        }// end class

}// end main

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What the problem is that this will partly work. It will replace one instance of the word the user inputs but after that it cuts everything else off. Also I know I can easily do this with the replace method but that is not what the teacher wants. It MUST be a while loop because that is what we as a class are focusing on right now. Any help is appreciated :)

For some reason I can't edit my post. Just wanted to say that I am not using the 'lengther' variable so ignore that.

Oof, been A while since I did this. Isn't there an indexOf method that looks for certain words? You could probably use that to seek out the replacee word.

I hope someone more knowledgeable comes to help out, sorry if I wasn't too much help. :c

A straightforward solution:

1. Split the string along the white space.
2. Store the resulting word-strings in an array (or linked list, I dunno what they've taught you yet).
3. Get the users choice.
4. Iterate over the array/list, using simple string comparisons to search for the user's chosen word.
5. Replace the chosen word (in the array/list) with a new one.
6. Reassemble message.

Easy enough.

Couple of questions: Are you specifically replacing single words, or are you replacing any substring? For example, if the sentence is:

"My cat is black"

Can the user replace "s bl" and replace it with "nhales cr"

so it becomes "My cat inhales crack" ? Or does it SPECIFICALLY have to be one word?

Did the teacher specify any input guarantees? (e.g. the input line will be just letters and single spaces separating them)

What if it's a sentence that ends with a period, and you want to replace the last word? If you just split on the space, you won't be able to compare with the last word. :)

Basically, you need to really carefully read over the problem description for these programming questions, and even state all your assumptions in the comments.


Finally, quick mini-feedback: You don't need those "placeholders" like where you go "String line1 = new String();"

It's fine to just do:

String line1 = checker.nextLine();


All strings in Java are immutable. It's actually bad style to declare those "placeholders" and serves no purpose. I hope your teacher didn't recommend it. :)

Otherwise, if it's safe to just assume words and spaces, Mzzkc's approach is just fine. When you re-assemble the string, use a StringBuilder, rather than a bunch of "+" operations.

Thanks for the input Replicon! My teacher wants the program to simply replace ONE word. So if the user inputs "Hello sir, are you ok sir?. and wants to replace the word "sir" with "man" then the output should be "Hello man, are you ok man?" The teacher just wants words and spaces replaced so Mzzkc's method is what I am going to use.