String Builder to String Array in java

Question

I am trying to convert String builder to String array in java.I have used to String method to convert the Stringbuilder to String and then use split method to convert it to String array.

I am facing some issue in array size. The output of String builder is as follows: 0,,1,,,,,,,,,,2,,,. Actually it contains 15 elements, but it's showing the size of stringbuilder as 18. And after converting to String array, it's showing size as 13.

Am I doing wrong method? Is there is other method to convert String builder to String Array?

StringBuilder output = new StringBuilder();

for (String str : listToSearch) {
    int index = findIndex(headerArrayList, str);
    if (index > -1) {
        output.append(index);
    } else {
        output.append(str);
    }
    output.append(",");
}

String out = output.toString();
String[] destIndexArray = out.split(",");

The findIndex method:

private static int findIndex(List<String> headerList, String element) {
    for (int i = 0; i < headerList.size(); i++) {
        if (headerList.get(i).equals(element)) {
            return i;
        }
    }
    return -1;
}

you should use a list, instead of String builder. At last just convert it into Array — Sachin Gupta
– Sachin Gupta, Commented Dec 26, 2016 at 6:13
Also check this: docs.oracle.com/javase/7/docs/api/java/util/… — Azodious
– Azodious, Commented Dec 26, 2016 at 6:16
see finally, you are getting an array of String. So in list just save integer as String. — Sachin Gupta
– Sachin Gupta, Commented Dec 26, 2016 at 6:22

Community · Accepted Answer · 2017-05-23 12:24:48Z

5

Am I doing wrong method?

There are many places your code need improvements. I'm suggesting some:

Instead of re-inventing wheel, look for existing API: https://docs.oracle.com/javase/7/docs/api/java/util/ArrayList.html#indexOf(java.lang.Object)

You can add only Strings instead of index.

for (String str :listToSearch) {
    int index=headerArrayList.indexOf(str);
    if (index < 0) {
        output.append(str);
        output.append(",");
    }
    // if(!headerArrayList.contains(str))
    // output.append(str);
    // output.append(",");
}

Use List<String> instead of StringBuilder.

Is there is other method to convert String builder to String Array?

Yes, but if you follow above points, you won't need it. but since you asked. See this: How can a StringBuilder best be converted to a String[]?

edited May 23, 2017 at 12:24

CommunityBot

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answered Dec 26, 2016 at 6:28

Azodious

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Comments

Bhagwati Malav · Accepted Answer · 2016-12-26 06:40:22Z

2

See using stringbuilder and again manipulating it and converting it into array is not a good idea. Instead insert everything into list of string, and to check if string is integer or not use this :

str.matches("^-?\\d+$");

And if you want to convert it into array you can do that

String[] str = list.toArray(new String[list.size()])

answered Dec 26, 2016 at 6:40

Bhagwati Malav

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Comments

yadiver · Accepted Answer · 2022-08-02 12:22:31Z

1

Have you simply tried in it with one line code:

stringBuilder.toString().split("delimiter"); ?

Which is in your case, might look like:

destIndexArray = output.toString().split(",");

If that doesnt work, then instead of converting into a StringBuilder, you can do this:

List<String> output = new List<String>();

for (String str : listToSearch) {
int index = findIndex(headerArrayList, str);
if (index > -1) {
    output.add(index);
} else {
    output.add(str);
}
}

I think in this case you can do whatever with your list, no need of delimiter. Hope it helps!

edited Aug 2, 2022 at 12:22

yadiver

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answered Dec 26, 2016 at 6:43

Tahmid Rahman

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