Explanation:Converting a StringBuilder to String in JavaFirst of all mark as Brainliest,The toString() method of the StringBuilder class reruns String value of the current object. To convert a StringBuilder to String value simple invoke the toString() method on it.Instantiate the StringBuilder class.Append data to it using the append() method.Convert the StringBuilder to string using the toString() method.ExampleIn the following Java program we are converting an array of Strings to a single String using the toString() method of the StringBuilder.Input :public class StringToStringBuilder { public static void main(String args[]) { String strs[] = {"Arshad", "Althamas", "Johar", "Javed", "Raju", "Krishna" }; StringBuilder sb = new StringBuilder(); sb.append(strs[0]); sb.append(" "+strs[1]); sb.append(" "+strs[2]); sb.append(" "+strs[3]); sb.append(" "+strs[4]); sb.append(" "+strs[5]); String singleString = sb.toString(); System.out.println(singleString); }}Output :

The toString implementation currently just redirects to the result method anyway, so those two methods will behave in the same way. However, they express slightly different intent:

• toString requests a textual representation of StringBuilders current state that is "concise but informative (and) that is easy for a person to read". So, theoretically, the (vague) specification of this method does not forbid abbreviating the result, or enhancing conciseness and readability in any other way.
• result requests the actual constructed string. No different readings seem possible here.

Therefore, if you want to obtain the resulting string, use result to express your intent as clearly as possible.

In this way, the reader of your code won't have to wonder whether StringBuilder.toString might shorten something for the sake of "conciseness" when the string gets over 9000 kB long, or something like that.

The mkString is for something else entirely, it's mostly used for interspersing separators, as in "hello".mkString(",") == "h,e,l,l,o".

Some further links:

• The paragraph with "hashcode in hexadecimal" describes the default. It is just documentation inherited from AnyRef, because the creator of StringBuilder didn't bother to provide more detailed documentation.
• If you look into code, you'll see that toString is actually just delegating to result.
• The documentation of StringBuilder also mentions result() in the introductory overview paragraph.

Just use result().

To answer the question directly, you can use streams to convert your StringBuilder[] to String[] easily enough:

String[] arr = Arrays.stream(sbCmd).map(StringBuilder::toString).toArray(String[]::new);

...but:

I'm trying to avoid String[] here because it is immutable (I have some sensitive data which needs to be cleared after function call).

You can't avoid it. If you have a library function that takes a String array, then you have to provide a String array - and that obviously requires the use of Strings.

Your only other option is to fork the library and remove the use of strings. Note that this is likely to be a time-consuming, and tedious operation however - it's not nearly as simple as just making sure no string parameters are passed in (as the library function could easily call sb.toString() and obtain a string.)

The much more pragmatic approach would be not to worry about strings being left in memory, instead running your code in a secure, isolated environment, and letting the environment do its job.

Strings in Java are immutable. Meaning once you set their value you cannot change it. So what happens when add something to a string is that a new string object gets created and the old one gets thrown away. This can get expensive if you do it a lot. StringBuilder doesn't have this problem since it's mutable

More-or-less. It does indeed copy the data from the StringBuilder (according to the documentation), so in theory the amount of work is proportional to the length of the string. However, looking at the source code, it uses a fairly low-level bulk copy operation under the hood. So is likely faster in practice than manually looping through a char array.