How to run JavaScript embedded in java program using Nashorn JavaScript Engine??

 Nashorn JavaScript Engine

              It is a JavaScript engine introduced in java8. It was developed by oracle. Now, it is under the OpenJDK community.

Purpose:

This is used to run the JavaScript code in JVM (Java Virtual Machine).

Why Nashorn?

It is efficient in execution compared to previous one (Rhino Engine).

It easily integrates java and JavaScript. The user can simply use the command line.

How to run JavaScript embedded in java program using Nashorn JavaScript Engine??

              Here, java Script is a single line which displays a greetings “Happy Programming”.

Steps:

• Import three built in packages from javax.script(.ScriptEngine,.ScriptEngineManager,.ScriptException)
• Create a public class NashornEg and save the file as “NashornEg.java”
• Inside the main() function,create an object for ScriptEngineManager as mgr.
• Get the Nashorn script Engine.
• Write a java script code.
• Eval the script by Object result1 = engine1.eval(script);
• Print the result.

import javax.script.ScriptEngine;

import javax.script.ScriptEngineManager;

import javax.script.ScriptException;

public class NashornEg {

    public static void main(String[] args) {

        // Create an object for ScriptEngineManager

        ScriptEngineManager mgr = new ScriptEngineManager();

       // find the Nashorn script engine

        ScriptEngine engine1 = mgr.getEngineByName("nashorn");

      // JavaScript code

        String script = "var greetings = 'Happy Programming!';";

        try {

            // create an object and call the function

            Object result1 = engine1.eval(script);

           // Print the output

            System.out.println(result1);

        } catch (ScriptException e) {

            e.printStackTrace();

        }

    }

}

• Compile the program.
• If the compilation is successful, run the program.

C:\raji\blog>javac NashornEg.java

C:\raji\blog>java NashornEg

Happy Programming!

Let us try some more scripting….

Java Script to display “Happy Birthday. Stay Blessed Always!!!!”.

Same program is used with java script code alone changed.

        String script = "var bMsg = 'Happy Birthday. Stay Blessed Always!!!!';";

Change the code. Execute the same program as below.

C:\raji\blog>javac NashornEg.java

C:\raji\blog>java NashornEg

Happy Birthday. Stay Blessed Always!!!!

That’s all. The java program to use JavaScript within the code is developed successfully.

Note: This JavaScript engine is used as standalone project on GitHub because it was deprecated in java11.

How to implement Static methods in interface concept in java8???

  The word “Static” is applicable for the interface. It does not be an instance of the class which implements the interface.

Why static method???

• ·       Scope of the static methods is visible within interface.
• ·       It belongs to interface only. So, utility methods are declared as static methods.

Simple program to implement static methods in interface:

              This program creates an interface with a static method “staticMd()” to print the static method message. Even though, a class is declared to implement the interface, the method belongs to the interface only.

//Java Program to implement static methods in interface

interface MyInter {

    static void staticMd() {

        System.out.println("This is a static method in an interface MyInter");

    }

}

public class MyCls implements MyInter {

    public static void main(String[] args) {

        MyInter.staticMd(); // Function call

    }

}

Save this file as “MyCls.java”.

Compile the program in command prompt.

C:\raji\blog>javac MyCls.java

Execute the program as follows. You will get this output.

C:\raji\blog>java MyCls

This is a static method in an interface MyInter.

 Next, a program for odd or even number checking is given below.

Java Program to implement Odd/Even number checking using static methods in interface:

              This java program has following steps to implement the concept.

• Create an interface “MyInter1”.
• Inside the interface, implement the static method as “static void staticOddEven(int a)”.

         Where,

        static – keyword.

        void – return type.(It doesn’t return anything)

        staticOddEven – this is the static function name.

        int a – input of a function as integer.

• This function checks the given number is odd or even and print it.
• Create a class “MyCls1” to implement the interface “MyInter1”.
• Inside it,create a main function.
• Call the static function “MyInter1.staticOddEven(6)”.

// Java Program to implement Odd/Even number checking using static methods in interface

interface MyInter1 {

    static void staticOddEven(int a) {

      if(a%2==0)

        System.out.println("The number is a even number");

      else

       System.out.println("The number is a even number");

          }

}

public class MyCls1 implements MyInter1 {

    public static void main(String[] args) {

        MyInter1.staticOddEven(6); // static method call

    }

}

Compile and run the program to get the output.

C:\raji\blog>javac MyCls1.java

C:\raji\blog>java MyCls1

The number is a even number

These are the ways to implement the static methods in interface concept in java8. Keep Coding!!!!