Java 8 Tutorial
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Java 8 - Nashorn JavaScript
Java 8 - Nashorn JavaScript
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 pne 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>
Calpng 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.ScriptEngineManager;
import javax.script.ScriptEngine;
import javax.script.ScriptException;
pubpc class Java8Tester {
pubpc 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
Calpng 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)).spanide(
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 −
78952000000000000003.20Advertisements