Java 11 Shebang example - Run As Shell Program

1. Introduction

In this tutorial, You'll be learning today how to run the java program as shell script files (shebang) from java terminal from Unix or mac os. Even you can run from docker as well. Copy the files to docker and make sure you have OpenJDK 11 installed and run with java 11 single source files command.

At the present time, You might have seen a lack of knowledge on shell programming or a bit difficult to maintain the scripts for back end jobs.

Now, Java 11 comes up with the new concept to execute the java files as shell script files like batch-job.sh file. Inside batch-job.sh file, you can write all your java code and it is completely understandable at runtime by the operating system.

2. Java 11 Shebang files - Run as Shell Programs

First, In general, you see in the shell script files that start with the shebang declaration as below.

#!/bin/sh

And next the script files can be executed as below.

$./start.sh

Finally, These types of files are called shebang files.

Now, you can run the java single source files with the shebang approach.

Add the following as the first line in the script file.

#!/usr/local/bin/java --source 11

Furthermore that statement you can add your normal program that can be run as .sh file.

Let us write a simple hello world program with a shebang.

#!/usr/local/bin/java --source 11
public class batchjob {
    public static void main(String[] args) {
        System.out.println("Hello World");
    }
}

Run from command prompt or terminal.

$ java batch-job.sh  1 3

Hello World

3. Java 11 Shebang Program to the sum of n numbers

As shown above, this is based on shebang style programs to find sum of n numbers.

#!/usr/local/bin/java --source 11
import java.util.stream.IntStream;


public class sum {
    public static void main(String[] args) {

       IntStream intStream =IntStream.range(1, 5);

        int output = intStream.sum();
        System.out.println("Sum of first 5 numbers = "+output);

    }
}

Output:

$ java batch-job.sh  1 3

Sum of first 5 numbers = 10

4. Shebang with --source 11 Options

If the file is saved as without .java extension then when you run the program as a script then you must be using --source option to tell the java that you are running shebang script.

Even though you have explicitly declared shebang in the file, it will be ignored by java it is considered as a normal java file without .java file extension.

Especially these are relevant while executing the files.

java --source 11 batch-job.sh  1 3

5. Java 11 Shebang - Source Option to the sum of numbers From Command Line Arguments

Java 11 single source files work well with command-line arguments also.

#!/usr/local/bin/java --source 11
import java.util.Arrays;
import java.util.stream.IntStream;
import java.util.stream.Stream;

public class sum {
    public static void main(String[] args) {

        Stream<String> stream = Arrays.stream(args);

        int sum = stream.mapToInt(Integer::parseInt).sum();
        System.out.println("Total sum : "+sum);
    }
}

Output:

 

$ java --source 11 batch-job.sh  1 3



Total sum : 4

$ java --source 11 batch-job.sh  1 3 5

Total sum : 9

$ java --source 11 batch-job.sh  1 3 5 7

Total sum : 16

6. Conclusion

In this article, You've seen how to run a java program as a shell script in java 11 (shebang files).

All the code is shown in this article is over GitHub.

You can download the project directly and can run in your local without any errors.

View on GitHub 

Download 

If you have any queries please post in the comment section.