[java/en] Fix minor typo

[ds2643]

This commit fixes a very minor typo in the java (English) tutorial.

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• [X] Pull request title is prepended with [language/lang-code] (example [python/fr-fr] or [java/en])
• [X] Pull request touches only one file (or a set of logically related files with similar changes made)
• [X] Content changes are aimed at intermediate to experienced programmers (this is a poor format for explaining fundamental programming concepts)
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  • [X] Yes, I have double-checked quotes and field names!