Project does not compile with Java 21 language level

[cushon]

Project does not compile with Java 21 language and API level.

The definition of namedGroups() clashes with a JDK API was added in JDK 20: https://bugs.openjdk.org/browse/JDK-8292872

Repro:

JAVA_HOME=<path to JDK 21> ant
...
    [javac] ./synoptic/src/synoptic/util/matching/NamedMatcher.java:107: error: namedGroups() in NamedMatcher cannot implement namedGroups() in MatchResult
    [javac]     public Map<String, String> namedGroups() {
    [javac]                                ^
    [javac]   return type Map<String,String> is not compatible with Map<String,Integer>
    [javac] ./synoptic/src/synoptic/util/matching/INamedMatchResult.java:15: error: namedGroups() in INamedMatchResult clashes with namedGroups() in MatchResult
    [javac]     Map<String, String> namedGroups();
    [javac]                         ^
    [javac]   return type Map<String,String> is not compatible with Map<String,Integer>

The repro requires updating the source version from 1.7 to 8, the latest javac versions to not support -source 1.7:

diff --git a/InvariMint/build.xml b/InvariMint/build.xml
index 6576fb28..2ab9b08b 100644
--- a/InvariMint/build.xml
+++ b/InvariMint/build.xml
@@ -18,8 +18,8 @@

        <property name="debuglevel" value="source,lines,vars"/>

-       <property name="target" value="1.7"/>
-    <property name="source" value="1.7"/>
+       <property name="target" value="8"/>
+    <property name="source" value="8"/>

     <!-- Where to find the generated synoptic classes. -->
     <path id="invarimint.classes.classpath">
diff --git a/csight/build.xml b/csight/build.xml
index 1548fb74..c80c4050 100644
--- a/csight/build.xml
+++ b/csight/build.xml
@@ -15,8 +15,8 @@
     <property name="csight.jarpath" value="${util.synoptic.libdir}/csight.jar"/>
     <property name="junit.output.dir" value="junit"/>
     <property name="debuglevel" value="source,lines,vars"/>
-    <property name="target" value="1.7"/>
-    <property name="source" value="1.7"/>
+    <property name="target" value="8"/>
+    <property name="source" value="8"/>

     <!-- Where to find the generated synoptic classes. -->
     <path id="csight.classes.classpath">
diff --git a/daikonizer/build.xml b/daikonizer/build.xml
index bc4269ec..7f23a34a 100644
--- a/daikonizer/build.xml
+++ b/daikonizer/build.xml
@@ -35,8 +35,8 @@
     </manifestclasspath>

     <property name="debuglevel" value="source,lines,vars"/>
-    <property name="target" value="1.7"/>
-    <property name="source" value="1.7"/>
+    <property name="target" value="8"/>
+    <property name="source" value="8"/>

     <!--=====================================================================-->
     <target name="clean">
diff --git a/synoptic/build.xml b/synoptic/build.xml
index a6731474..0612f10b 100644
--- a/synoptic/build.xml
+++ b/synoptic/build.xml
@@ -45,8 +45,8 @@
     </manifestclasspath>

     <property name="debuglevel" value="source,lines,vars"/>
-    <property name="target" value="1.7"/>
-    <property name="source" value="1.7"/>
+    <property name="target" value="8"/>
+    <property name="source" value="8"/>

     <!--=====================================================================-->
     <target name="clean">
diff --git a/synopticjung/build.xml b/synopticjung/build.xml
index 98942bb2..2a7c8e09 100644
--- a/synopticjung/build.xml
+++ b/synopticjung/build.xml
@@ -4,8 +4,8 @@
     <property environment="env"/>
     <property name="SYNOPTIC_LIB" value="../lib"/>
     <property name="debuglevel" value="source,lines,vars"/>
-    <property name="target" value="1.7"/>
-    <property name="source" value="1.7"/>
+    <property name="target" value="8"/>
+    <property name="source" value="8"/>

        <path id="SynopticJung.classpath">
         <pathelement location="bin"/>