Convert range of a Character[] to String

Question

I have the array : ['a','b','c','d']

I want to take a certain range of the array, say [0,2] and make this a string. The result would be "abc".

This solution actually works :

private static String convertPartArrayToString(char[] array, int startIndex, int endIndex) {
    char[] dest = new char[endIndex - startIndex + 1];
    System.arraycopy( array, startIndex, dest, 0, endIndex - startIndex + 1 );
    return new String(dest);
}

But isn't there a way to make this faster than to copy the array?

Possible duplicate of [Grab a segment of an array in Java without creating a new array on heap](http://stackoverflow.com/questions/1100371/grab-a-segment-of-an-array-in-java-without-creating-a-new-array-on-heap) — maraca, Nov 19 '15 at 15:11
Possible duplicate of http://stackoverflow.com/questions/5283444/convert-array-of-strings-into-a-string-in-java — Aragorn, Nov 19 '15 at 15:13
Given the fact that `String` is immutable you have to copy the (part of) the array — Manos Nikolaidis, Nov 19 '15 at 15:14
you can just use something like `return new String(array).substring(startIndex,endIndex);` — alias_boubou, Nov 19 '15 at 15:16
@alias_boubou That would copy the whole array and then copy only the subset required. :) — Michael Lloyd Lee mlk, Nov 19 '15 at 15:19

score 2 · Accepted Answer · edited Nov 19 '15 at 17:01

2

String has a constructor that takes an array of char, a start and count.

The array will still be (defensively) copied as otherwise mutable state will escape and you will no longer have an immutable String.

edited Nov 19 '15 at 17:01

Jordi Castilla

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answered Nov 19 '15 at 15:16

Michael Lloyd Lee mlk

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The reason I didn't use that is because I didn't know it existed! :p – IEatBagels Nov 19 '15 at 15:19
1

Word of warning - The ctor (and the methods suggested by Jordi Castilla use an offset and a count, not a "to-from" as you use in your example. Not a large problem, but one to be aware off. You will always have a defensive copy as otherwise the state will escape and the string will no longer be mutable. It comes down to which reads better. I'd use the ctor as I'm constructing a string. But that me. – Michael Lloyd Lee mlk Nov 19 '15 at 15:27

Jordi Castilla · Answer 2 · 2015-11-19T15:26:19.187

1

You have plenty of JAVA built in methods, in this case you are using System API, wich is not really usual in this cases, instead of this you can use:

`Arrays API`:

private static String convertPartArrayToString(char[] array, int from, int to) {  
    return Arrays.toString(Arrays.copyRange(array, from, to);
}

`String API`

copyValueOf(char[], int, int)

private static String convertPartArrayToString(char[] array, int from, int to) {  
    return String.copyValueOf(array, from, to - from);
}

edited Nov 19 '15 at 15:26

answered Nov 19 '15 at 15:12

Jordi Castilla

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@mlk you are of course correct. And there is actually a shorter version `String.valueOf(array, from, count)` – Manos Nikolaidis Nov 19 '15 at 15:29

Convert range of a Character[] to String

2 Answers2

Arrays API:

String API

`Arrays API`:

`String API`