simple example of jjs - utility to invoke the Nashorn engine, which is a Java 8 implementation of es5/6 which can utility Java classes

filerev.js

/* 
   filerev.js

   demo of jjs, takes stdin or list of files and takes entirety of buffer
   or list of files, reads them into memory and prints them in reverse order.

   awful code, purely to demonstrate the interaction between js and Java in the
   Nashorn platform.

   example 1:

      $ jjs ./filerev.js -- file1.txt file2.txt file3.txt
      

   example 2:

      $ cat file.txt | jjs filerev.js

*/

function MultipleFileReader(files) {
    this.files = files;
    this.currentFileIndex = 0;
    this.currentFile = this.openNext();
}

MultipleFileReader.prototype.openNext = function() {
    if ( this.currentFileIndex < this.files.length) {
	return new java.io.BufferedReader(
	    new java.io.FileReader(this.files[this.currentFileIndex++])
	);
    } else {
	return null;
    }    
}

MultipleFileReader.prototype.readLine = function() {
    if (this.currentFile == null || this.currentFileIndex > this.files.length) {
	return null;
    }

    var line = this.currentFile.readLine();

    if ( line != null && line.length > 0 ) {
	return line;
    } else {
	this.currentFile = this.openNext();
	if ( this.currentFile != null ) {
	    return this.readLine();
	}
	else {
	    return null;
	}
    }
}

function getInputReader(args) {
    if (args.length > 0 ) {
	return new MultipleFileReader(args);
    }

    return new java.io.BufferedReader(
	new java.io.InputStreamReader(java.lang.System.in)
    );
v}

var input = getInputReader(arguments);

var allLines = new java.util.ArrayList();

var line = input.readLine();

while ( line != null && line.length != 0 ) {
    allLines.add(line);
    line = input.readLine();
}

java.util.Collections.reverse(allLines);

allLines.forEach(function(e, i, a) {
    print(e);
});