See Programmer's Guide to Text Blocks for more information about this language feature.
This is a preview feature, which is a feature whose design, specification, and implementation are complete, but is not permanent, which means that the feature may exist in a different form or not at all in future JDK releases. To compile and run code that contains preview features, you must specify additional command-line options. See Preview Features.
For background information about text blocks, see JEP 368.