runtime(java): Recognise string templates (#14150)

As this is encouraged in the referenced JEPs, "to visually
distinguish a string template from a string literal, and
a text block template from a text block", the default
colours for java\%[Debug]StrTempl are made distinct from
java\%[Debug]String.

According to §3.2 Lexical Translations (JLS, c. 1996 or any
more recent version), line terminators, white space, and
comments are discarded before tokens are accepted. Since
a template expression comprises a template processor, a dot,
and a template, it may be visually appealing to break up
its head across a few lines whenever its tail already spans
multiple lines.  Curiously, no allowance for it is made in
the distributed tests for OpenJDK 21; the proposed regexp
patterns take in consideration a line terminator and white
space after a dot.

References:
https://openjdk.org/jeps/430 (Preview)
https://openjdk.org/jeps/459 (Second Preview)
https://openjdk.org/jeps/465

Signed-off-by: Aliaksei Budavei <0x000c70@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

9 files changed, 165 insertions, 35 deletions

diff --git a/runtime/syntax/java.vim b/runtime/syntax/java.vim
index f6d2660277..c059de603c 100644
--- a/runtime/syntax/java.vim
+++ b/runtime/syntax/java.vim
@@ -2,7 +2,7 @@
 " Language:	Java
 " Maintainer:	Claudio Fleiner <claudio@fleiner.com>
 " URL:          https://github.com/fleiner/vim/blob/master/runtime/syntax/java.vim
-" Last Change:	2024 Mar 02
+" Last Change:	2024 Mar 06
 
 " Please check :help java.vim for comments on some of the options available.
 
@@ -187,8 +187,8 @@ if exists("java_comment_strings")
   syn match   javaCommentCharacter contained "'\\[^']\{1,6\}'" contains=javaSpecialChar
   syn match   javaCommentCharacter contained "'\\''" contains=javaSpecialChar
   syn match   javaCommentCharacter contained "'[^\\]'"
-  syn cluster javaCommentSpecial add=javaCommentString,javaCommentCharacter,javaNumber
-  syn cluster javaCommentSpecial2 add=javaComment2String,javaCommentCharacter,javaNumber
+  syn cluster javaCommentSpecial add=javaCommentString,javaCommentCharacter,javaNumber,javaStrTempl
+  syn cluster javaCommentSpecial2 add=javaComment2String,javaCommentCharacter,javaNumber,javaStrTempl
 endif
 
 syn region  javaComment		 start="/\*"  end="\*/" contains=@javaCommentSpecial,javaTodo,@Spell
@@ -234,6 +234,9 @@ syn match   javaSpecialChar	 contained "\\\%(u\x\x\x\x\|[0-3]\o\o\|\o\o\=\|[bstn
 syn region  javaString		start=+"+ end=+"+ end=+$+ contains=javaSpecialChar,javaSpecialError,@Spell
 syn region  javaString		start=+"""[ \t\x0c\r]*$+hs=e+1 end=+"""+he=s-1 contains=javaSpecialChar,javaSpecialError,javaTextBlockError,@Spell
 syn match   javaTextBlockError	+"""\s*"""+
+syn region  javaStrTemplEmbExp	 contained matchgroup=javaStrTempl start="\\{" end="}" contains=TOP
+syn region  javaStrTempl	 start=+\%(\.[[:space:]\n]*\)\@<="+ end=+"+ contains=javaStrTemplEmbExp,javaSpecialChar,javaSpecialError,@Spell
+syn region  javaStrTempl	 start=+\%(\.[[:space:]\n]*\)\@<="""[ \t\x0c\r]*$+hs=e+1 end=+"""+he=s-1 contains=javaStrTemplEmbExp,javaSpecialChar,javaSpecialError,javaTextBlockError,@Spell
 " The next line is commented out, it can cause a crash for a long line
 "syn match   javaStringError	  +"\%([^"\\]\|\\.\)*$+
 syn match   javaCharacter	 "'[^']*'" contains=javaSpecialChar,javaSpecialCharError
@@ -254,7 +257,7 @@ syn match   javaNumber		 "\<0[xX]\%(\x\%(_*\x\)*\.\=\|\%(\x\%(_*\x\)*\)\=\.\x\%(
 " Unicode characters
 syn match   javaSpecial "\\u\x\x\x\x"
 
-syn cluster javaTop add=javaString,javaCharacter,javaNumber,javaSpecial,javaStringError,javaTextBlockError
+syn cluster javaTop add=javaString,javaStrTempl,javaCharacter,javaNumber,javaSpecial,javaStringError,javaTextBlockError
 
 if exists("java_highlight_functions")
   if java_highlight_functions == "indent"
@@ -280,7 +283,12 @@ if exists("java_highlight_debug")
   syn match   javaDebugSpecial		contained "\\\%(u\x\x\x\x\|[0-3]\o\o\|\o\o\=\|[bstnfr"'\\]\)"
   syn region  javaDebugString		contained start=+"+  end=+"+  contains=javaDebugSpecial
   syn region  javaDebugString		contained start=+"""[ \t\x0c\r]*$+hs=e+1 end=+"""+he=s-1 contains=javaDebugSpecial,javaDebugTextBlockError
-" The next line is commented out, it can cause a crash for a long line
+  " The highlight groups of java{StrTempl,Debug{,Paren,StrTempl}}\,
+  " share one colour by default. Do not conflate unrelated parens.
+  syn region  javaDebugStrTemplEmbExp	contained matchgroup=javaDebugStrTempl start="\\{" end="}" contains=javaComment,javaLineComment,javaDebug\%(Paren\)\@!.*
+  syn region  javaDebugStrTempl		contained start=+\%(\.[[:space:]\n]*\)\@<="+ end=+"+ contains=javaDebugStrTemplEmbExp,javaDebugSpecial
+  syn region  javaDebugStrTempl		contained start=+\%(\.[[:space:]\n]*\)\@<="""[ \t\x0c\r]*$+hs=e+1 end=+"""+he=s-1 contains=javaDebugStrTemplEmbExp,javaDebugSpecial,javaDebugTextBlockError
+  " The next line is commented out, it can cause a crash for a long line
 " syn match   javaDebugStringError	contained +"\%([^"\\]\|\\.\)*$+
   syn match   javaDebugTextBlockError	contained +"""\s*"""+
   syn match   javaDebugCharacter	contained "'[^\\]'"
@@ -307,6 +315,7 @@ if exists("java_highlight_debug")
 
   hi def link javaDebug		 Debug
   hi def link javaDebugString		 DebugString
+  hi def link javaDebugStrTempl		 Macro
   hi def link javaDebugStringError	 javaError
   hi def link javaDebugTextBlockError	 javaDebugStringError
   hi def link javaDebugType		 DebugType
@@ -376,6 +385,7 @@ hi def link javaSpecial		Special
 hi def link javaSpecialError		Error
 hi def link javaSpecialCharError	Error
 hi def link javaString			String
+hi def link javaStrTempl		Macro
 hi def link javaCharacter		Character
 hi def link javaSpecialChar		SpecialChar
 hi def link javaNumber			Number
diff --git a/runtime/syntax/testdir/dumps/java_string_00.dump b/runtime/syntax/testdir/dumps/java_string_00.dump
index b973226f13..0d2f148f2d 100644
--- a/runtime/syntax/testdir/dumps/java_string_00.dump
+++ b/runtime/syntax/testdir/dumps/java_string_00.dump
@@ -1,4 +1,4 @@
->c+0#00e0003#ffffff0|l|a|s@1| +0#0000000&|S|t|r|i|n|g|T|e|s|t|s| @57
+>c+0#00e0003#ffffff0|l|a|s@1| +0#0000000&|S|t|r|i|n|g|T|e|s|t|s| @2|/+0#0000e05&@1| |J|D|K| |2|1|+| |(|-@1|e|n|a|b|l|e|-|p|r|e|v|i|e|w| |-@1|r|e|l|e|a|s|e| |2|1|)|.| +0#0000000&@11
 |{| @73
 @4|s+0#00e0003&|t|a|t|i|c| +0#0000000&|{| @62
 @8|S|t|r|i|n|g| |s|1| |=| |"+0#e000002&|A| |q|u|i|c|k| |b|r|o|w|n| |f|o|x| |j|u|m|p|s| |o|v|e|r| |t|h|e| |l|a|z|y| |d|o|g|"|;+0#0000000&| @10
diff --git a/runtime/syntax/testdir/dumps/java_string_01.dump b/runtime/syntax/testdir/dumps/java_string_01.dump
index d7035611a7..84b6494589 100644
--- a/runtime/syntax/testdir/dumps/java_string_01.dump
+++ b/runtime/syntax/testdir/dumps/java_string_01.dump
@@ -17,4 +17,4 @@
 @8|/+0#0000e05&@1| |T|h|e|r|e| |a|r|e| |S|P|A|C|E|,| |F@1|,| |H|T|,| |C|R|,| |a|n|d| |L|F| |a|f|t|e|r| |"@2|.| +0#0000000&@17
 @8|S|t|r|i|n|g| |e|m|p|t|y| |=| |"@2| |^+0#0000e05&|L| +0#0000000&@2|^+0#0000e05&|M| +0#0000000&@40
 | +0#e000002&@11|"+0#0000000&@2|;| @58
-@57|1|9|,|3|-|9| @7|5|2|%| 
+@57|1|9|,|3|-|9| @7|1|5|%| 
diff --git a/runtime/syntax/testdir/dumps/java_string_02.dump b/runtime/syntax/testdir/dumps/java_string_02.dump
index e0b0ae08e3..ef6549f55a 100644
--- a/runtime/syntax/testdir/dumps/java_string_02.dump
+++ b/runtime/syntax/testdir/dumps/java_string_02.dump
@@ -9,12 +9,12 @@
 | +0#e000002&@7|"@1|\+0#e000e06&|"|"+0#e000002&@1|\+0#e000e06&|u|0@1|5|c|\|u|0@1|2@1| +0#0000000&@48
 | +0#e000002&@7|"@1|\+0#e000e06&|"|"+0#e000002&@1|\+0#e000e06&|"|"+0#e000002&| +0#0000000&@57
 | +0#e000002&@7|"@1|\+0#e000e06&|"|"+0#e000002&@1|\+0#e000e06&|"|"+0#e000002&|\+0#e000e06&|"|"+0#0000000&@2|)|;| @50
-@4|}| @69
-|}| @73
-|~+0#4040ff13&| @73
-|~| @73
-|~| @73
-|~| @73
-|~| @73
-|~| @73
-| +0#0000000&@56|3|7|,|3|-|9| @7|B|o|t| 
+@75
+@8|S|y|s|t|e|m|.|o|u|t|.|p|r|i|n|t|l|n|(|S|T|R|.|"@2| @40
+| +0#e000e06&@7|"| +0#0000000&@65
+| +0#e000e06&@7|\|{|"+0#e000002&|\+0#e000e06&|"|\|"|"+0#e000002&|}+0#e000e06&| +0#0000000&@57
+| +0#e000e06&@7|\|{|"+0#e000002&|\+0#e000e06&|"|\|"|"+0#e000002&|}+0#e000e06&|\|{|"+0#e000002&|\+0#e000e06&|u|0@1|5|c|\|u|0@1|2@1|"+0#e000002&|}+0#e000e06&| +0#0000000&@40
+| +0#e000e06&@7|\|{|"+0#e000002&|\+0#e000e06&|"|\|"|"+0#e000002&|}+0#e000e06&|\|{|"+0#e000002&|\+0#e000e06&|u|0@1|5|c|\|u|0@1|2@1|"+0#e000002&|}+0#e000e06&|"| +0#0000000&@39
+| +0#e000e06&@7|\|{|"+0#e000002&|\+0#e000e06&|"|\|"|"+0#e000002&|}+0#e000e06&|\|"|\|{|"+0#e000002&|\+0#e000e06&|u|0@1|5|c|\|u|0@1|2@1|\|u|0@1|5|c|\|u|0@1|2@1|"+0#e000002&|}+0#e000e06&| +0#0000000&@26
+| +0#e000e06&@7|\|{|"+0#e000002&|\+0#e000e06&|"|\|"|"+0#e000002&|}+0#e000e06&|\|"|\|{|"+0#e000002&|\+0#e000e06&|"|\|"|"+0#e000002&|}+0#e000e06&|\|{|"+0#e000002&|\+0#e000e06&|u|0@1|5|c|\|u|0@1|2@1|"+0#e000002&|}+0#e000e06&| +0#0000000&@29
+@57|3|7|,|3|-|9| @7|3|6|%| 
diff --git a/runtime/syntax/testdir/dumps/java_string_03.dump b/runtime/syntax/testdir/dumps/java_string_03.dump
new file mode 100644
index 0000000000..9e88372b28
--- /dev/null
+++ b/runtime/syntax/testdir/dumps/java_string_03.dump
@@ -0,0 +1,20 @@
+| +0#e000e06#ffffff0@7|\|{|"+0#e000002&|\+0#e000e06&|"|\|"|"+0#e000002&|}+0#e000e06&|\|"|\|{|"+0#e000002&|\+0#e000e06&|"|\|"|"+0#e000002&|}+0#e000e06&|\|{|"+0#e000002&|\+0#e000e06&|u|0@1|5|c|\|u|0@1|2@1|"+0#e000002&|}+0#e000e06&| +0#0000000&@29
+| +0#e000e06&@7|\|{|"+0#e000002&|\+0#e000e06&|"|\|"|"+0#e000002&|}+0#e000e06&|\|"|\|{|"+0#e000002&|\+0#e000e06&|"|\|"|"+0#e000002&|}+0#e000e06&|\|"@1| +0#0000000&@43
+| +0#e000e06&@7|\|{|"+0#e000002&|\+0#e000e06&|"|\|"|"+0#e000002&|}+0#e000e06&|\|"|\|{|"+0#e000002&|\+0#e000e06&|"|\|"|"+0#e000002&|}+0#e000e06&|\|"@1|\|"|"+0#0000000&@2|)|;| @5|/+0#0000e05&@1| |J|D|K| |2|1|+|.| +0#0000000&@19
+@75
+@8|S|t|r|i|n|g| |w|o@1|f| |=| |"+0#e000002&|W|o@1|f|"|,+0#0000000&| |d|o|g| |=| |"+0#e000002&|d|o|g|"|,+0#0000000&| |f|o|x| |=| |"+0#e000002&|f|o|x|"|;+0#0000000&| @19
+> @74
+@8|S|t|r|i|n|g| |s|6| |=| |S|T|R| @51
+@12|.|"+0#e000e06&|A| |q|u|i|c|k| |b|r|o|w|n| |\|{|f+0#0000000&|o|x|}+0#e000e06&| |j|u|m|p|s| |o|v|e|r| |t|h|e| |l|a|z|y| |\|{|d+0#0000000&|o|g|}+0#e000e06&|"|;+0#0000000&| @11
+@8|S|t|r|i|n|g| |s|7| |=| |S|T|R|.|p|r|o|c|e|s@1|(|S|t|r|i|n|g|T|e|m|p|l|a|t|e|.|R|A|W| @24
+@12|.|"+0#e000e06&|\|"|\|{|w+0#0000000&|o@1|f|}+0#e000e06&|\|s|!|\|"@1|)+0#0000000&|;| @43
+@8|S|t|r|i|n|g| |s|8| |=| |S|T|R|.|"@2| @47
+| +0#e000e06&@11|A|\|s|\| +0#0000000&@58
+| +0#e000e06&@11|q|u|i|c|k| |\| +0#0000000&@55
+| +0#e000e06&@11|b|r|o|w|n|\|s|\| +0#0000000&@54
+| +0#e000e06&@11|\|{|f+0#0000000&|o|x|}+0#e000e06&| |\| +0#0000000&@54
+| +0#e000e06&@11|j|u|m|p|s|\|s|\| +0#0000000&@54
+| +0#e000e06&@11|o|v|e|r| |\| +0#0000000&@56
+| +0#e000e06&@11|t|h|e|\|s|\| +0#0000000&@56
+| +0#e000e06&@11|l|a|z|y| |\| +0#0000000&@56
+@57|5@1|,|0|-|1| @7|5|7|%| 
diff --git a/runtime/syntax/testdir/dumps/java_string_04.dump b/runtime/syntax/testdir/dumps/java_string_04.dump
new file mode 100644
index 0000000000..4336a92b2d
--- /dev/null
+++ b/runtime/syntax/testdir/dumps/java_string_04.dump
@@ -0,0 +1,20 @@
+| +0#e000e06#ffffff0@11|l|a|z|y| |\| +0#0000000&@56
+| +0#e000e06&@11|\|{|d+0#0000000&|o|g|}+0#e000e06&|"+0#0000000&@2|;| @52
+@8|S|t|r|i|n|g| |s|9| |=| |S|T|R|.|p|r|o|c|e|s@1|(|S|t|r|i|n|g|T|e|m|p|l|a|t|e|.|R|A|W| @24
+@12|.| @61
+@12|"@2| @59
+| +0#e000e06&@11>"|\|{|w+0#0000000&|o@1|f|}+0#e000e06&|\|s|!|\|"|"+0#0000000&@2|)|;| @44
+@8|S|t|r|i|n|g| |s|1|0| |=| |j|a|v|a|.|u|t|i|l|.|F|o|r|m|a|t|P|r|o|c|e|s@1|o|r|.|F|M|T| @24
+@12|.| |"+0#e000e06&|%|-|1|4|s|\|{|"+0#e000002&|A|\+0#e000e06&|s|"+0#e000002&| +0#0000000&|+| |S|T|R| |.| |"+0#e000e06&|q|u|i|c|k|"| +0#0000000&|+| |"+0#e000002&|b|r|o|w|n|"|}+0#e000e06&|%|s|\|{|f+0#0000000&|o|x|}+0#e000e06&| |"| +0#0000000&@10
+@12|+| |j|a|v|a|.|u|t|i|l|.|F|o|r|m|a|t|P|r|o|c|e|s@1|o|r|.|F|M|T| @31
+@12|.| |"+0#e000e06&|%|-|2|0|s|\|{|"+0#e000002&|j|u|m|p|s|\+0#e000e06&|s|o+0#e000002&|v|e|r| |t|h|e|\+0#e000e06&|s|"+0#e000002&| +0#0000000&@33
+@20|+| |S|T|R| |.| |"+0#e000e06&|l|a|z|y|"|}|%|s|\|{|d+0#0000000&|o|g|}+0#e000e06&|"|;+0#0000000&| @29
+@8|S|t|r|i|n|g| |s|1@1| |=| |S|T|R|.|"@2| @46
+| +0#e000e06&@11|\|"|\|{| +0#0000000&@11|/+0#0000e05&@1| |A| |n|e|s|t|e|d| |c|o|m@1|e|n|t|.| +0#0000000&@26
+@8|(|n+0#af5f00255&|e|w| +0#0000000&|j|a|v|a|.|u|t|i|l|.|f|u|n|c|t|i|o|n|.|F|u|n|c|t|i|o|n|<|S|t|r|i|n|g|,| |S|t|r|i|n|g|>|(|)| |{| @14
+@12|p+0#00e0003&|u|b|l|i|c| +0#0000000&|S|t|r|i|n|g| |a|p@1|l|y|(|S|t|r|i|n|g| |b|a|y|)| |{| |r+0#af5f00255&|e|t|u|r|n| +0#0000000&|b|a|y|;| |}|;| @14
+@8|}|)|.|a|p@1|l|y|(|w|o@1|f|)| @52
+@12|}+0#e000e06&|\|s|!|\|"|"+0#0000000&@2|;| @52
+@8|S|t|r|i|n|g| |s|1|2| |=| |j|a|v|a|.|u|t|i|l|.|F|o|r|m|a|t|P|r|o|c|e|s@1|o|r|.|F|M|T| @24
+@12|.|"@2| @58
+@57|7|3|,|4|-|1|3| @6|7|8|%| 
diff --git a/runtime/syntax/testdir/dumps/java_string_05.dump b/runtime/syntax/testdir/dumps/java_string_05.dump
new file mode 100644
index 0000000000..47804a9393
--- /dev/null
+++ b/runtime/syntax/testdir/dumps/java_string_05.dump
@@ -0,0 +1,20 @@
+| +0&#ffffff0@11|.|"@2| @58
+| +0#e000e06&@11|%|-|1|4|s|\|{|S+0#0000000&|T|R|.|"@2| @48
+| +0#e000e06&@15|A|\|s|\| +0#0000000&@54
+| +0#e000e06&@15|\|{| +0#0000000&|"+0#e000002&|q|u|i|c|k|"| +0#0000000&|}+0#e000e06&| |\| +0#0000000&@44
+| +0#e000e06&@15|b|r|o|w|n|"+0#0000000&@2|}+0#e000e06&|\| +0#0000000&@48
+| +0#e000e06&@11>%|s|\|{| +0#0000000&|f|o|x| |}+0#e000e06&| |\| +0#0000000&@50
+| +0#e000e06&@11|%|-|2|0|s|\|{|S+0#0000000&|T|R|.|"@2| @48
+| +0#e000e06&@15|j|u|m|p|s|\|s|\| +0#0000000&@50
+| +0#e000e06&@15|o|v|e|r| |\| +0#0000000&@52
+| +0#e000e06&@15|t|h|e|\|s|\| +0#0000000&@52
+| +0#e000e06&@15|\|{| +0#0000000&|"+0#e000002&|l|a|z|y|"| +0#0000000&|}+0#e000e06&| |"+0#0000000&@2|}+0#e000e06&|\| +0#0000000&@41
+| +0#e000e06&@11|%|s|\|{| +0#0000000&|d|o|g| |}+0#e000e06&|"+0#0000000&@2|;| @48
+@8|S|t|r|i|n|g| |s|1|3| |=| |S|T|R| @50
+@12|.|"+0#e000e06&|\|"|\|{| +0#0000000&@9|/+0#0000e05&|*| |A| |n|e|s|t|e|d| |c|o|m@1|e|n|t|.| |*|/| +0#0000000&@23
+@8|(@1|j|a|v|a|.|u|t|i|l|.|f|u|n|c|t|i|o|n|.|F|u|n|c|t|i|o|n|<|S|t|r|i|n|g|,| |S|t|r|i|n|g|>|)| |b|a|y| |-|>| |b|a|y|)| @8
+@28|.|a|p@1|l|y|(|w|o@1|f|)| @34
+@12|}+0#e000e06&|\|s|!|\|"@1|;+0#0000000&| @54
+@4|}| @69
+|}| @73
+@57|9|1|,|4|-|1|3| @6|B|o|t| 
diff --git a/runtime/syntax/testdir/dumps/java_string_99.dump b/runtime/syntax/testdir/dumps/java_string_99.dump
index f147db8095..a401ad664c 100644
--- a/runtime/syntax/testdir/dumps/java_string_99.dump
+++ b/runtime/syntax/testdir/dumps/java_string_99.dump
@@ -1,20 +1,20 @@
-| +0#e000002#ffffff0@11|t|h|e|\+0#e000e06&@1|s+0#e000002&|\+0#e000e06&@1| +0#0000000&@54
-| +0#e000002&@11|l|a|z|y| |\+0#e000e06&@1| +0#0000000&@55
-| +0#e000002&@11|d|o|g|\+0#e000e06&|"|"+0#e000002&@1|;|"+0#0000000&@2|;| @50
-@75
-@8|/+0#0000e05&@1| |T|h|e|r|e| |a|r|e| |S|P|A|C|E|,| |F@1|,| |H|T|,| |C|R|,| |a|n|d| |L|F| |a|f|t|e|r| |"@2|.| +0#0000000&@17
-@8|S|t|r|i|n|g| |e|m|p|t|y| |=| |"@2| |^+0#0000e05&|L| +0#0000000&@2|^+0#0000e05&|M| +0#0000000&@40
-| +0#e000002&@11|"+0#0000000&@2|;| @58
-@75
-@8|S|y|s|t|e|m|.|o|u|t|.|p|r|i|n|t|l|n|(|"@2| @44
-| +0#e000002&@7|"| +0#0000000&@65
-| +0#e000002&@7|"@1| +0#0000000&@64
-| +0#e000002&@7|"@1|\+0#e000e06&|u|0@1|5|c|"+0#e000002&| +0#0000000&@57
-| +0#e000002&@7|"@1|\+0#e000e06&|u|0@1|5|c|"+0#e000002&@1| +0#0000000&@56
-| +0#e000002&@7|"@1|\+0#e000e06&|"|\|u|0@1|2@1|\|u|0@1|2@1| +0#0000000&@50
-| +0#e000002&@7|"@1|\+0#e000e06&|"|"+0#e000002&@1|\+0#e000e06&|u|0@1|5|c|\|u|0@1|2@1| +0#0000000&@48
-| +0#e000002&@7|"@1|\+0#e000e06&|"|"+0#e000002&@1|\+0#e000e06&|"|"+0#e000002&| +0#0000000&@57
-| +0#e000002&@7|"@1|\+0#e000e06&|"|"+0#e000002&@1|\+0#e000e06&|"|"+0#e000002&|\+0#e000e06&|"|"+0#0000000&@2|)|;| @50
+| +0&#ffffff0@11|.|"@2| @58
+| +0#e000e06&@11|%|-|1|4|s|\|{|S+0#0000000&|T|R|.|"@2| @48
+| +0#e000e06&@15|A|\|s|\| +0#0000000&@54
+| +0#e000e06&@15|\|{| +0#0000000&|"+0#e000002&|q|u|i|c|k|"| +0#0000000&|}+0#e000e06&| |\| +0#0000000&@44
+| +0#e000e06&@15|b|r|o|w|n|"+0#0000000&@2|}+0#e000e06&|\| +0#0000000&@48
+| +0#e000e06&@11|%|s|\|{| +0#0000000&|f|o|x| |}+0#e000e06&| |\| +0#0000000&@50
+| +0#e000e06&@11|%|-|2|0|s|\|{|S+0#0000000&|T|R|.|"@2| @48
+| +0#e000e06&@15|j|u|m|p|s|\|s|\| +0#0000000&@50
+| +0#e000e06&@15|o|v|e|r| |\| +0#0000000&@52
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+| +0#e000e06&@11|%|s|\|{| +0#0000000&|d|o|g| |}+0#e000e06&|"+0#0000000&@2|;| @48
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+@12|.|"+0#e000e06&|\|"|\|{| +0#0000000&@9|/+0#0000e05&|*| |A| |n|e|s|t|e|d| |c|o|m@1|e|n|t|.| |*|/| +0#0000000&@23
+@8|(@1|j|a|v|a|.|u|t|i|l|.|f|u|n|c|t|i|o|n|.|F|u|n|c|t|i|o|n|<|S|t|r|i|n|g|,| |S|t|r|i|n|g|>|)| |b|a|y| |-|>| |b|a|y|)| @8
+@28|.|a|p@1|l|y|(|w|o@1|f|)| @34
+@12|}+0#e000e06&|\|s|!|\|"@1|;+0#0000000&| @54
 @4|}| @69
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-@57|4@1|,|1| @9|B|o|t| 
+@57|1|0|4|,|1| @8|B|o|t| 
diff --git a/runtime/syntax/testdir/input/java_string.java b/runtime/syntax/testdir/input/java_string.java
index 51c30b9da8..43a7a050ca 100644
--- a/runtime/syntax/testdir/input/java_string.java
+++ b/runtime/syntax/testdir/input/java_string.java
@@ -1,4 +1,4 @@
-class StringTests
+class StringTests	// JDK 21+ (--enable-preview --release 21).
 {
 	static {
 		String s1 = "A quick brown fox jumps over the lazy dog";
@@ -40,5 +40,65 @@ class StringTests
 		""\"""\u005c\u0022
 		""\"""\""
 		""\"""\""\"""");
+
+		System.out.println(STR."""
+		"
+		\{"\"\""}
+		\{"\"\""}\{"\u005c\u0022"}
+		\{"\"\""}\{"\u005c\u0022"}"
+		\{"\"\""}\"\{"\u005c\u0022\u005c\u0022"}
+		\{"\"\""}\"\{"\"\""}\{"\u005c\u0022"}
+		\{"\"\""}\"\{"\"\""}\""
+		\{"\"\""}\"\{"\"\""}\""\"""");		// JDK 21+.
+
+		String woof = "Woof", dog = "dog", fox = "fox";
+
+		String s6 = STR
+			."A quick brown \{fox} jumps over the lazy \{dog}";
+		String s7 = STR.process(StringTemplate.RAW
+			."\"\{woof}\s!\"");
+		String s8 = STR."""
+			A\s\
+			quick \
+			brown\s\
+			\{fox} \
+			jumps\s\
+			over \
+			the\s\
+			lazy \
+			\{dog}""";
+		String s9 = STR.process(StringTemplate.RAW
+			.
+			"""
+			"\{woof}\s!\"""");
+		String s10 = java.util.FormatProcessor.FMT
+			. "%-14s\{"A\s" + STR . "quick" + "brown"}%s\{fox} "
+			+ java.util.FormatProcessor.FMT
+			. "%-20s\{"jumps\sover the\s"
+					+ STR . "lazy"}%s\{dog}";
+		String s11 = STR."""
+			\"\{			// A nested comment.
+		(new java.util.function.Function<String, String>() {
+			public String apply(String bay) { return bay; };
+		}).apply(woof)
+			}\s!\"""";
+		String s12 = java.util.FormatProcessor.FMT
+			."""
+			%-14s\{STR."""
+				A\s\
+				\{ "quick" } \
+				brown"""}\
+			%s\{ fox } \
+			%-20s\{STR."""
+				jumps\s\
+				over \
+				the\s\
+				\{ "lazy" } """}\
+			%s\{ dog }""";
+		String s13 = STR
+			."\"\{			/* A nested comment. */
+		((java.util.function.Function<String, String>) bay -> bay)
+							.apply(woof)
+			}\s!\"";
 	}
 }