Removing letters from a string using a while loop in Java

Question

while (sentence.indexOf(lookFor) > lookFor)
{
    sentence += sentence.substring(sentence.indexOf(lookFor));
}
String cleaned = sentence;
return cleaned;

This is what I have tried to do in order to remove letters. lookFor is a char that was put in already, and sentence is the original sentence string that was put in already. Currently, my code outputs the sentence without doing anything to it.
EX Correct Output: inputting "abababa" sentence; char as "a" --->outputting "bbb" inputting "xyxyxy" sentence; char "a" ---> outputting "xyxyxy"

sentence.indexOf(lookFor) > lookFor You're comparing the position of the character in a string to the character itself. That doesn't make any sense. — mkasberg
– mkasberg, Commented Oct 13, 2015 at 21:18
sentence += ... You'll never remove anything from sentence this way. It will only get longer. — mkasberg
– mkasberg, Commented Oct 13, 2015 at 21:19
Why don't you show us the whole function, with input parameters, return value, and samples of expected input/output? — mkasberg
– mkasberg, Commented Oct 13, 2015 at 21:19
what you need to do is print out each part of the code. print out sentence.indexOf(lookFor) before you use it. — ergonaut
– ergonaut, Commented Oct 13, 2015 at 21:21

Jürgen K. · Accepted Answer · 2015-10-13 21:21:33Z

4

You don't need while for a single string. Only if you read a text line after line. In your case something like

String a = "abababa";
a = a.replace("a","");

would give you the output "bbb"

answered Oct 13, 2015 at 21:21

Jürgen K.

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1 Comment

anlam456 Over a year ago

Thanks for the advice, but for this assignment, I have to use a while loop to solve this. I am also inputting several strings. Sorry for not making that clear.

Tea Curran · Accepted Answer · 2015-10-13 21:26:04Z

0

it probably isn't entering the loop at all.

sentence.indexOf(lookFor) is going to return the place of the character in the string.

lookFor is a char value. A value of 'a' has a numeric value of 97 so the while will only find things after the first 97 characters.

If your code ever entered the loop it would never return.

the substring command you are calling will take the found item to the end of the string.

+=, if it did what you think will append it to itself. so it will take 'ababab' and make it 'abababababab', forever. but luckily you can't use += on a string in java.

What you want is:

String something = "abababab";
something = something.replaceAll("a", "");

answered Oct 13, 2015 at 21:26

Tea Curran

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3 Comments

Jürgen K. Over a year ago

Actually your answer is a combination from the comments and my answer;)

Tom Over a year ago

It is always a good idea to avoid replaceAll if you're not using a (real) regular expression.

Tea Curran Over a year ago

@JürgenK. hah. when I started typing there were no comments or answers. When I finished there were a ton. Such an easy question that happens. I up-voted your answer. and Tom, yeah you're right but I figured an example with a replace would just generate a question about replacing a non-char value.

stack smasher · Accepted Answer · 2015-10-13 21:30:22Z

-1

If you just need to get rid of letters use the replace method that others have written, but if you want to use a while loop, based on what I've seen of your logic, this is how you'd do it.

while (sentence.indexOf(lookFor) == 0)
    sentence = sentence.substring(1);
while (sentence.indexOf(lookFor) > 0)
{
    sentence = sentence.substring(0, sentence.indexOf(lookFor)-1)+
               sentence.substring(sentence.indexOf(lookFor)+1);
}
return sentence;

edited Oct 13, 2015 at 21:30

answered Oct 13, 2015 at 21:25

stack smasher

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6 Comments

Jazzwave06 Over a year ago

This create 3 String object for each loop iteration, while trashing the old one. Your garbage collection will sky rocket if applied to a text.

stack smasher Over a year ago

There are obviously better ways accomplish OP's task, but based on what we've seen of his logic, this is probably what he was trying to do. Sorry but he never gave any restrictions on garbage collection

anlam456 Over a year ago

Thank you for this! This worked out for me, but I'm not understanding the bit where the substrings are added together.

Jazzwave06 Over a year ago

Ok so if someone ask you how to use a gun on is temple, you'll show him exactly how to do it? Op obviously has no clue about garbage collection. Teach him instead of giving him bad advices.

stack smasher Over a year ago

@anlam456 where you add the substrings is concatenation. sentence.substring(0, sentence.indexOf(lookFor)-1) gives you the substring of the entire string up to the letter you want to get rid of; sentence.substring(sentence.indexOf(lookFor)+1) gives you everything after the letter you want to get rid of

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