def action(user, password)

ScriptEngineManager m = new ScriptEngineManager();
ScriptEngine jruby = m.getEngineByName("jruby");

// Load script.rb resource.
ClassLoader classloader = Thread.currentThread().getContextClassLoader();
InputStream is = classloader.getResourceAsStream("script.rb");
BufferedReader reader = new BufferedReader(new InputStreamReader(is));
jruby.eval(reader);

jruby.put("user", "TestUser");
jruby.put("password", "xyz!"); // I'd like to pass "xyz!" as a char array.

// Call the script.
String result = (String)jruby.eval("action($user, $password)");

char[] password = { 'x', 'y', 'z', '!' };
jruby.put("password", password);
...

pwd = ['x', 'y', 'z', '!'].to_s
// use pwd inside the script ...

pwd = ['x', 'y', 'z', '!'].to_s
pwd = pwd.force_encoding("UTF-8")
// use pwd inside the script ...