RFR: 8298033: Character.codePointAt(char[], int, int) doesn't do JavaDoc-specified check

[Sergey Tsypanov]

I found out that this code

public class Main {
    public static void main(String[] args) {
        String s = "Hello world!";
        char[] chars = s.toCharArray();
        int point = Character.codePointAt(chars, -1, 1);
    }
}

throws `ArrayIndexOutOfBoundsException` instead of JavaDoc-specified `IndexOutOfBoundsException`: 

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: Index -1 out of bounds for length 12
	at java.base/java.lang.Character.codePointAtImpl(Character.java:9254)
	at java.base/java.lang.Character.codePointAt(Character.java:9249)
	at org.example.Main.main(Main.java:7)

and the method doesn't check whether `index` parameter is negative:

public static int codePointAt(char[] a, int index, int limit) {
    if (index >= limit || limit < 0 || limit > a.length) {
        throw new IndexOutOfBoundsException();
    }
    return codePointAtImpl(a, index, limit);
}

I suggest to check the `index` parameter explicitly instead of relying on AIOOBE thrown from accessing the array with negative index.

-------------

Commit messages:
 - 8298033: Character.codePointAt(char[], int, int) doesn't do JavaDoc-specified check

Changes: https://git.openjdk.org/jdk/pull/11480/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11480&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8298033
  Stats: 2 lines in 1 file changed: 0 ins; 1 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/11480.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11480/head:pull/11480

PR: https://git.openjdk.org/jdk/pull/11480