Java 8 has provided a new JavaScript engine i.e. 'Nashorn', to run JavaScript files in Java.
Nashorn provides 2 to 10 times better performance, as it directly compiles the code in memory and passes the bytecode to JVM.
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
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 :-
1. Compile the class using javac compiler as follows −
C:\JAVA>javac Java8Tester.java
2. 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
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