From c376b8ffa5b4ccabf9f5d75fe8a69b715af065de Mon Sep 17 00:00:00 2001
From: Axel Kohlmeyer <akohlmey@gmail.com>
Date: Sun, 18 Oct 2020 01:49:19 -0400
Subject: [PATCH] add java interface

---
 swig/CMakeLists.txt      |  9 +++++++++
 swig/run_java_example.sh | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 43 insertions(+)
 create mode 100755 swig/run_java_example.sh

diff --git a/swig/CMakeLists.txt b/swig/CMakeLists.txt
index 18c6ac3195..cadafba076 100644
--- a/swig/CMakeLists.txt
+++ b/swig/CMakeLists.txt
@@ -16,11 +16,20 @@ endif()
 find_package(SWIG REQUIRED)
 include(${SWIG_USE_FILE})
 
+option(BUILD_SWIG_JAVA "Build Java JNI wrapper with SWIG" OFF)
 option(BUILD_SWIG_LUA "Build Lua wrapper with SWIG" OFF)
 option(BUILD_SWIG_PERL5 "Build Perl5 wrapper with SWIG" OFF)
 option(BUILD_SWIG_PYTHON "Build Python wrapper with SWIG" OFF)
 option(BUILD_SWIG_TCL "Build Tcl wrapper with SWIG" OFF)
 
+if(BUILD_SWIG_JAVA)
+  set_property(SOURCE lammps.i PROPERTY SWIG_MODULE_NAME javalammps)
+  swig_add_library(javalammps TYPE MODULE LANGUAGE java SOURCES lammps.i)
+  find_package(JNI REQUIRED)
+  target_include_directories(javalammps PRIVATE ${JNI_INCLUDE_DIRS})
+  swig_link_libraries(javalammps PRIVATE lammps ${JNI_LIBRARIES})
+endif()
+
 if(BUILD_SWIG_PYTHON)
   set_property(SOURCE lammps.i PROPERTY SWIG_MODULE_NAME pylammps)
   swig_add_library(pylammps TYPE MODULE LANGUAGE python SOURCES lammps.i)
diff --git a/swig/run_java_example.sh b/swig/run_java_example.sh
new file mode 100755
index 0000000000..09975049dd
--- /dev/null
+++ b/swig/run_java_example.sh
@@ -0,0 +1,34 @@
+#!/bin/sh
+
+cat > example.java <<EOF
+public class example {
+  static {
+    System.loadLibrary("javalammps");
+  }
+
+  public static void main(String argv[]) {
+    SWIGTYPE_p_void lmp = javalammps.lammps_open_no_mpi(0, null, null);
+    int ver = javalammps.lammps_version(lmp);
+
+    javalammps.lammps_command(lmp, "units real");
+    javalammps.lammps_command(lmp, "lattice fcc 2.5");
+    javalammps.lammps_command(lmp, "region box block -5 5 -5 5 -5 5");
+    javalammps.lammps_command(lmp, "create_box 1 box");
+    javalammps.lammps_command(lmp, "create_atoms 1 box");
+
+    System.out.print("LAMMPS version ");
+    System.out.println(ver);
+    System.out.print("Number of created atoms: ");
+    System.out.println(javalammps.lammps_get_natoms(lmp));
+    javalammps.lammps_close(lmp);
+  }
+}
+EOF
+
+CLASSPATH=$PWD:${CLASSPATH-${PWD}}
+LD_LIBRARY_PATH=$PWD:${LD_LIBARARY_PATH-${PWD}}
+
+export CLASSPATH LD_LIBRARY_PATH
+
+javac *.java
+java example