RFR: 8266625: The method DiagnosticSource#findLine returns wrong results when using the boundary values

[Guoxiong Li]

Hi all,

Currently, when the file object has N characters, the method `DiagnosticSource#findLine(N)` returns true, which is a wrong result. Becase the position is zero-based, the max index is `N-1`.

The methods `getLineNumber`, `getColumnNumber` and `getLine`, which use `findLine` internally, would also return wrong results when using the boundary values.

This patch mainly fixes `DiagnosticSource#findLine(N)` by using the following code.


-            return bp <= bufLen;
+            return bp < bufLen;


A corresponding test `DiagnosticSourceTest.java` is added. Then, the usages of  `getLineNumber`, `getColumnNumber` and `getLine` need to revised. And two existing tests need to be adjusted.

Thank you for taking the time to review.

Best Regards,
--- Guoxiong

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Commit messages:
 - 8266625: The method DiagnosticSource#findLine returns wrong results when using the boundary values

Changes: https://git.openjdk.java.net/jdk/pull/3899/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3899&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8266625
  Stats: 124 lines in 8 files changed: 117 ins; 0 del; 7 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3899.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3899/head:pull/3899

PR: https://git.openjdk.java.net/jdk/pull/3899