CODEWITHSUNDEEP
java
jciecka
jciecka

Reputation: 15

StringIndexOutOfBoundsException error from stringbuilder within a while loop

The assignment is to, for example, remove char 'a' from the String "I am Sam am I Sam", this is a bit code I have so far:

public String removeLetters() {
    String cleaned=sentence;
    StringBuilder builder = new StringBuilder(cleaned);

    while(cleaned.indexOf(lookFor) != -1) {
        builder.deleteCharAt(cleaned.indexOf(lookFor));
    }
    return builder.toString();
}

This method returns fine when there's no while loop (though it only removes one char), but when I run it with the while loop I get the OutOfBounds error.

Upvotes: 1

Views: 1397

Answers (5)

sdanzig
sdanzig

Reputation: 4500

Have to remove from the builder, not the source string. Also, you initially had an infinite loop, attempting to modify the builder string, but only checking the source string, which wouldn't change. This compiled and ran fine:

public String removeLetters()
{
    String lookFor = "a";
    String original="I am Sam am I Sam";
    StringBuilder builder = new StringBuilder(original);
    while(builder.indexOf(lookFor) != -1) {
        builder.deleteCharAt(builder.indexOf(lookFor));
    }
    return builder.toString();
}

Upvotes: 0

Prabhakaran Ramaswamy
Prabhakaran Ramaswamy

Reputation: 26094

try this one.

cleaned.replaceAll(lookFor,"");

Upvotes: 0

Mureinik
Mureinik

Reputation: 310993

The condition in the while loop is the index in the cleaned StringBuilder, but then you're using the same index to delete characters from builder - after the first character has been deleted, they no longer match.

In short:

public String removeLetters() {
    String cleaned=sentence;
    StringBuilder builder = new StringBuilder(cleaned);

    while(builder.indexOf(lookFor) != -1) {
        builder.deleteCharAt(builder.indexOf(lookFor));
    }

    return builder.toString();
}

Upvotes: 0

Rohit Jain
Rohit Jain

Reputation: 213193

You can directly do this using String#replace method:

String cleaned = "I am Sam am I Sam";
cleaned = cleaned.replace("a", "");
System.out.println(cleaned);   // I m Sm m I Sm

Upvotes: 1

Piovezan
Piovezan

Reputation: 3223

Change this:

while(cleaned.indexOf(lookFor) != -1) {
    builder.deleteCharAt(cleaned.indexOf(lookFor));
}

with this:

while(builder.indexOf(Character.toString(lookFor)) != -1) {
    builder.deleteCharAt(builder.indexOf(Character.toString(lookFor)));
}

Upvotes: 1

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