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With Java 8, Nashorn, a much improved javascript engine is introduced, to replace the existing Rhino. Nashorn provides 2 to 10 times better performance, as it directly compiles the code in memory and passes the bytecode to JVM. Nashorn uses invoke dynamics feature, introduced in Java 7 to improve performance.

jjs

For Nashorn engine, JAVA 8 introduces a new command line tool, jjs, to execute javascript codes at console.

Interpreting js File

Create and save the file sample.js in c:\> JAVA folder.

sample.js

print('Hello World!');

Open console and use the following command.

C:\JAVA>jjs sample.js

It will produce the following output:

Hello World!

jjs in Interactive Mode

Open the console and use the following command.

C:\JAVA>jjs
jjs> print("Hello, World!")
Hello, World!
jjs> quit()
>>

Pass Arguments

Open the console and use the following command.

C:\JAVA> jjs -- a b c
jjs> print('letters: ' +arguments.join(", "))
letters: a, b, c
jjs>

Calling JavaScript from Java

Using ScriptEngineManager, JavaScript code can be called and interpreted in Java.

Example

Create the following Java program using any editor of your choice in, say, C:\> JAVA.

Java8Tester.java

 Live Demo

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 = "Mahesh"; Integer result = null; try { nashorn.eval("print('" + name + "')"); result = (Integer) nashorn.eval("10 + 2"); } catch(ScriptException e) { System.out.println("Error executing script: "+ e.getMessage()); } System.out.println(result.toString()); } }

Verify the Result

Compile the class using javac compiler as follows −

C:\JAVA>javac Java8Tester.java

Now run the Java8Tester as follows −

C:\JAVA>java Java8Tester

It should produce the following result −

Mahesh
12

Calling Java from JavaScript

The following example explains how to import and use Java classes in java script.

Create and save sample.js in c:\> JAVA folder.

sample.js

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);

Open the console and use the following command.

C:\JAVA>jjs sample.js

It should produce the following output −

78952000000000000003.20
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