Only in JPype1-1.4.1: JPype1-java8compat.patch
--- JPype1-1.4.1/native/build.xml	2020-07-17 00:34:07.000000000 +0200
+++ JPype1-1.4.1/native/build.xml	2023-06-12 11:24:36.344297754 +0200
@@ -1,7 +1,7 @@
 <project default="all" name="JPype - Native">
 
 	<!-- JAVA_VERSION must match the oldest supported Java version -->
-	<property name="JAVA_VERSION" value="1.8" />
+	<property name="JAVA_VERSION" value="8" />
 
 	<!-- src can't be "java" as it breaks nose tests -->
 	<property name="src" location="java"/>
@@ -16,6 +16,7 @@
 		<javac destdir="${build}/classes"
 			source="${JAVA_VERSION}"
 			target="${JAVA_VERSION}"
+			release="${JAVA_VERSION}"
 			excludes="**/JPypeClassLoader.java"
 			>
 			<src path="${src}"/>
@@ -23,6 +24,7 @@
 		<javac destdir="${build}/lib"
 			source="${JAVA_VERSION}"
 			target="${JAVA_VERSION}"
+			release="${JAVA_VERSION}"
 			includes="**/JPypeClassLoader.java"
 			>
 			<src path="${src}"/>
--- JPype1-1.4.1/test/build.xml	2020-07-17 00:34:07.000000000 +0200
+++ JPype1-1.4.1/test/build.xml	2023-06-12 12:47:52.223097870 +0200
@@ -20,8 +20,6 @@
 
 	<target name="compile-9" if="build-9">
 		<javac destdir="${build}"
-			source="${version}"
-			target="${version}"
 			>
 			<compilerarg value="--add-exports"/>
 			<compilerarg value="java.base/jdk.internal.reflect=ALL-UNNAMED"/>
@@ -34,8 +32,9 @@
 
 	<target name="compile-8" if="build-8">
 		<javac destdir="${build}"
-			source="${version}"
-			target="${version}"
+			source="8"
+			target="8"
+			release="8"
 			>
 			<src>
 				<pathelement location="${src}/java8"/>
@@ -47,8 +46,9 @@
 	<target name="compile-main">
 		<mkdir dir="${build}"/>
 		<javac destdir="${build}"
-			source="${version}"
-			target="${version}"
+			source="8"
+			target="8"
+			release="8"
 			debug="true"
 			debuglevel="lines,vars,source"
 			>