Fix statistics in RocksJava sample

[sagar0]

I observed while doing a make jtest that the java sample was broken, due to the changes in #2551 .

Test Plan:
Before the fix:

cd rocksdb/java
make sample
javac -Xlint:deprecation -Xlint:unchecked -cp target/classes -d samples/target/classes samples/src/main/java/RocksDBSample.java
samples/src/main/java/RocksDBSample.java:44: error: cannot find symbol
            .createStatistics()
            ^
  symbol:   method createStatistics()
  location: class Options
samples/src/main/java/RocksDBSample.java:54: error: cannot find symbol
      final Statistics stats = options.statisticsPtr();
                                      ^
  symbol:   method statisticsPtr()
  location: variable options of type Options
samples/src/main/java/RocksDBSample.java:207: warning: [deprecation] remove(byte[]) in RocksDB has been deprecated
        db.remove(testKey);
          ^
2 errors
1 warning
make[1]: *** [sample] Error 1

After the fix:
No errors on doing a make jtest or make sample

[adamretter]

Looks good. However Statistics is a RocksObject and so should ideally be manually closed, along with ReadOptions. Probably best to put them in a try-with-resources

[sagar0]

But both Statistics and ReadOptions are already in try-with-resources here.

[adamretter]

Sorry you are of course correct. I did not see it initially in the GitHub diff view. Sorry.

[adamretter]

Just needs a try-with-resources

[adamretter]

Looks good.

[facebook-github-bot]

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