Java 8 Nashorn JavaScript

Java 8 New Features

Nashorn is a javascript engine.

Nashorn JavaScript Engine in Java 15 is no longer available.

This has already been disabled in Java 11 is marked as:

@deprecated (forRemoval = true)

From JDK 1.8 Nashorn has replaced Rhino (JDK 1.6Starting from1.7, JDK 5.1 ) as the embedded JavaScript engine of Java. Nashorn fully supports ECMAScript 292 specification and some extensions. It uses a JSR 7 The invokedynamic introduced in the new language features included in JDK

Compared with the previous Rhino implementation, this brings 2 to 　10times performance improvement.

jjs

jjs is a command-line tool based on the Nashorn engine. It accepts some JavaScript source code as parameters and executes these source codes.

For example, we create a sample.js file with the following content:

print('Hello World!');

Open the console and enter the following command:

$ jjs sample.js

The output result of the above program is:

Hello World!

jjs Interactive Programming

Open the console and enter the following command:

$ jjs
jjs> print("Hello, World!")
Hello, World!
jjs> quit()
>>

Passing parameters

Open the console and enter the following command:

$ jjs　--　a b c
jjs> print('Letters: ')　+arguments.join(", "))
Letters: a, b, c
jjs>

Calling JavaScript in Java

Using ScriptEngineManager, JavaScript code can be executed in Java, as shown in the following example:

import javax.script.ScriptEngineManager;
import javax.script.ScriptEngine;
import javax.script.ScriptException;
　
public class Java8Tester {
　　　public static void main(String args[]){
　　　
　　　　　　ScriptEngineManager scriptEngineManager = new ScriptEngineManager();
　　　　　　ScriptEngine nashorn = scriptEngineManager.getEngineByName("nashorn");
　　　　　　　　
　　　　　　String name = "w3codebox";
　　　　　　Integer result = null;
　　　　　　
　　　　　　try {
　　　　　　　　　nashorn.eval("print('"　+　name　+　")");
　　　　　　　　　result = (Integer) nashorn.eval("10　+　2");
　　　　　　　　　
　　　　　　catch(ScriptException e){
　　　　　　　　　System.out.println("Execution script error: ");+　e.getMessage());
　　　　　　}
　　　　　　
　　　　　　System.out.println(result.toString());
　　　}
}

Execute the above script, and the output result is:

$ javac Java8Tester.java　
$ java Java8Tester
w3codebox
12

Calling Java in JavaScript

The following example demonstrates how to reference Java classes in JavaScript:

var BigDecimal = Java.type('java.math.BigDecimal');
function calculate(amount, percentage) {
　　　var result = new BigDecimal(amount).multiply(
　　　new BigDecimal(percentage)).divide(new BigDecimal("100"),　2, BigDecimal.ROUND_HALF_EVEN);
　　　
　　　return result.toPlainString();
}
var result = calculate(568000000000000000023,13.9);
print(result);

We use the jjs command to execute the above script, and the output is as follows:

$ jjs sample.js
78952000000000002017.94

Java 8 New Features