Scripting in Java Tutorial - Scripting in Java Output

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Nashorn provides has three functions to output text to the standard output:

• print() function
• printf() function
• echo() function

The echo() function is the same as the print() function and it works only in scripting mode.

print() function

The print() function is a varargs function. We can pass any number of arguments to it.

print() function converts its arguments to string and prints them separating them by a space.

print() function prints a new line at the each output.

The following two calls to the print() function returns the same value.

print("Hello", "World!"); // Prints Hello World!
print("Hello World!");    // Prints Hello World!

Full source code

import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
/*  ww w  . j a  va  2s  .  c om*/
public class Main {
  public static void main(String[] args) throws Exception{
    ScriptEngineManager manager = new ScriptEngineManager();
    ScriptEngine engine = manager.getEngineByName("JavaScript");
    String script = "print('Hello', 'World!');";
    engine.eval(script);
    script = "print('Hello World!');";
    engine.eval(script);
  }
}

The code above generates the following result.

printf() function

printf() function uses printf-style to format printing.

It is the same as using the Java method System.out.printf():

import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
//w w w .j  ava 2s  .  c  o  m
public class Main {
  public static void main(String[] args) throws Exception{
    ScriptEngineManager manager = new ScriptEngineManager();
    ScriptEngine engine = manager.getEngineByName("JavaScript");
    String script = "printf('%d + %d = %d', 1, 2, 1 + 2);";
    engine.eval(script);
  }
}

The code above generates the following result.

Output script execution result

The following code shows how to write output of a script execution to a file named jsoutput.txt.

import java.io.File;
import java.io.FileWriter;
/*  w ww  . ja v  a2 s . c om*/
import javax.script.ScriptContext;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;

public class Main {
  public static void main(String[] args) throws Exception {
    ScriptEngineManager manager = new ScriptEngineManager();
    ScriptEngine engine = manager.getEngineByName("JavaScript");

    File outputFile = new File("jsoutput.txt");
    System.out.println("Script output will be written to "
        + outputFile.getAbsolutePath());

    FileWriter writer = new FileWriter(outputFile);
    ScriptContext defaultCtx = engine.getContext();
    defaultCtx.setWriter(writer);
    String script = "print('Hello custom output writer')";
    engine.eval(script);
    writer.close();

  }
}

The code above generates the following result.

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