RFR: 8170389: java.text.DigitList.getDouble() : Controversy between javadoc and code

[Justin Lu]

Problem: Outdated doc does not match code. Claimed to throw exception and compared to Long method.
Fix: Update doc to match code, compared to Double.parseDouble() accordingly.

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Commit messages:
 - Update java doc to reflect code

Changes: https://git.openjdk.org/jdk/pull/10567/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10567&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8170389
  Stats: 2 lines in 1 file changed: 0 ins; 1 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/10567.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10567/head:pull/10567

PR: https://git.openjdk.org/jdk/pull/10567