Summary
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Text blocks were proposed by JEP 355 in early 2019 as a follow-on to explorations begun in JEP 326 (Raw String Literals), which was targeted to JDK 12 but later withdrawn. JEP 355 was targeted to JDK 13 in June 2019 as a preview feature. Feedback on JDK 13 suggested that the feature should be previewed again, with the addition of two new escape sequences, so the successor JEP 368 was targeted to JDK 14 in November 2019. Feedback on JDK 14 suggests that the Text Blocks feature is now ready to be made final and permanent.

Problem
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The preview status of Text Blocks prevents usage in standard Java.

Solution
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Remove the preview status requirement from Text Blocks.

Specification
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See attachment below for spec updates.

As a consequence of becoming a standard feature, messages emitted by `javac` for using a preview feature, etc. no longer occur.