Add another nashorn sample of dynamically invoking java code at runtime

src/com/winterbe/java8/Nashorn7.java

+package com.winterbe.java8;
+
+import javax.script.Invocable;
+import javax.script.ScriptEngine;
+import javax.script.ScriptEngineManager;
+import javax.script.ScriptException;
+
+/**
+ * @author Benjamin Winterberg
+ */
+public class Nashorn7 {
+
+    public static class Person {
+        private String name;
+
+        public String getName() {
+            return name;
+        }
+
+        public void setName(String name) {
+            this.name = name;
+        }
+
+        public int getLengthOfName() {
+            return name.length();
+        }
+    }
+
+    public static void main(String[] args) throws ScriptException, NoSuchMethodException {
+        ScriptEngine engine = new ScriptEngineManager().getEngineByName("nashorn");
+        engine.eval("function foo(predicate, obj) { return !!(eval(predicate)); };");
+
+        Invocable invocable = (Invocable) engine;
+
+        Person person = new Person();
+        person.setName("Hans");
+
+        String predicate = "obj.getLengthOfName() >= 4";
+        Object result = invocable.invokeFunction("foo", predicate, person);
+        System.out.println(result);
+    }
+
+}