Extract substring from a string

Question

what is the best way to extract a substring from a string in android?

Answer 1

The best way to get substring in Android is using (as @user2503849 said) TextUtlis.substring(CharSequence, int, int) method. I can explain why. If you will take a look at the String.substring(int, int) method from android.jar (newest API 22), you will see:

public String substring(int start) {
    if (start == 0) {
        return this;
    }
    if (start >= 0 && start <= count) {
        return new String(offset + start, count - start, value);
    }
    throw indexAndLength(start);
}

Ok, than... How do you think the private constructor String(int, int, char[]) looks like?

String(int offset, int charCount, char[] chars) {
    this.value = chars;
    this.offset = offset;
    this.count = charCount;
}

As we can see it keeps reference to the "old" value char[] array. So, the GC can not free it.

In the newest Java it was fixed:

String(int offset, int charCount, char[] chars) {
    this.value = Arrays.copyOfRange(chars, offset, offset + charCount);
    this.offset = offset;
    this.count = charCount;
}

Arrays.copyOfRange(...) uses native array copying inside.

That's it :)

Best regards!