not able to execute R script from java program?

I have a Rscript in a String variable and I want to execute it from Java program and pass some variable to it. If I execute that R script standalone, it works fine. I have converted that R script to one line by escaping it everything by using Python program as shown below:

import json

jsonstr = json.dumps({"script": """\
#!/usr/bin/Rscript

# read the data file
library('jsonlite')
library('rpart')

args <- as.list(Sys.getenv(c(
                        "path",
                        "client_users")))

if (args[["path"]]==""){
    args[["path"]] <- "."
}

# other stuff here
# other stuff here

"""})

print jsonstr

I use the printed string out and store it in String variable and then I am executing with below code and it doesn't work at all. I am passing path and client_users variable to above R script.

public static void main(String[] args) throws IOException, InterruptedException {

    // this is your script in a string
    // String script = "#!/bin/bash\n\necho \"Hello World\"\n\n readonly PARAM1=$param1\n echo $PARAM1\n\nreadonly PARAM2=$param2\n echo $PARAM2\n\n";
    String script = "above R Script here";

    List<String> commandList = new ArrayList<>();
    commandList.add("/bin/bash");

    ProcessBuilder builder = new ProcessBuilder(commandList);
    builder.environment().put("path", "/home/david");
    builder.environment().put("client_users", "1000");
    builder.redirectErrorStream(true);
    Process shell = builder.start();

    // Send your script to the input of the shell, something
    // like doing cat script.sh | bash in the terminal
    try(OutputStream commands = shell.getOutputStream()) {
        commands.write(script.getBytes());
    }

    // read the outcome
    try(BufferedReader reader = new BufferedReader(new InputStreamReader(shell.getInputStream()))) {
        String line;
        while((line = reader.readLine()) != null) {
            System.out.println(line);
        }
    }

    // check the exit code
    int exitCode = shell.waitFor();
    System.out.println("EXIT CODE: " + exitCode);
}

Above code works fine with bash shell script. Is there anything I need to do special for R script? I will be using same code for bash script and R scripts as well.

And this is the error I am getting:

/bin/bash: line 7: -: No such file or directory /bin/bash: line 10: syntax error near unexpected token `'jsonlite'' /bin/bash: line 10: `library('jsonlite')' 

And if I remove commandList.add("/bin/bash"); and add commandList.add("/bin/Rscript"); then I see below error:

Cannot run program "/bin/Rscript": error=2, No such file or directory

Update:-

Instead of using my above script, I decided to use simple print hell script in r to see whether I can execute it through Java or not.

// this will print hello
String script = "#!/usr/bin/env Rscript\nsayHello <- function(){\n   print('hello')\n}\n\nsayHello()\n";

When I execute this script with commandList.add("/bin/bash");, I get this error:

/bin/bash: line 2: syntax error near unexpected token `('
/bin/bash: line 2: `sayHello <- function(){'

But if I execute with this commandList.add("/bin/sh");, I get this error:

/bin/sh: 2: Syntax error: "(" unexpected