How to pass multiple integers from Bash shell script to Java System.in?

I need to pass two integer numbers from Bash shell script to my Java program.

Here is my Java code.

import java.util.Scanner;

public class ConsoleApp {
  public static void main(String[] args) {
    int x = getInt();
    int y = getInt();
    System.out.println("x = " + x);
    System.out.println("y = " + y);
  }

  private static int getInt() {
    Scanner s = new Scanner(System.in);
    return s.nextInt();
  }
}

Here it's the Bash script and the name of script is run.sh.

#!/usr/bin/env bash

declare -r AppName=ConsoleApp

function compile() {
  javac $AppName.java
}

function execute() {
  echo 1 2 | java $AppName
}

compile; execute;

$ chmod a+x run.sh
$ ./run.sh

After I execute, it occurs the following error message.

Exception in thread "main" java.util.NoSuchElementException
        at java.base/java.util.Scanner.throwFor(Scanner.java:937)
        at java.base/java.util.Scanner.next(Scanner.java:1594)
        at java.base/java.util.Scanner.nextInt(Scanner.java:2258)
        at java.base/java.util.Scanner.nextInt(Scanner.java:2212)
        at ConsoleApp.getInt(ConsoleApp.java:13)
        at ConsoleApp.main(ConsoleApp.java:6)

For now, I know it can read the first integer number x but can't read the second integer number y.

You have to use the same scanner for both numbers:

  Scanner s = new Scanner(System.in);
  int x = s.nextInt();
  int y = s.nextInt();
  System.out.println("x = " + x);
  System.out.println("y = " + y);

Otherwise the first scanner will consume more data from System.in than the first number and store the remaining data in an internal buffer for further processing. If you then switch to another scanner that data is lost and the new scanner will read from System.in again but there is nothing more left.

Alternatively, it may be easier to pass the two numbers as command line arguments via the args argument.

Create a single Scanner.

import java.util.Scanner;

public class ConsoleApp {
  public static void main(String[] args) {
    Scanner s = new Scanner(System.in);
    int x = getInt(s);
    int y = getInt(s);
    System.out.println("x = " + x);
    System.out.println("y = " + y);
  }

  private static int getInt(Scanner s) {
    return s.nextInt();
  }
}

Use a heredoc in your Bash script.

#!/usr/bin/env bash

declare -r AppName=ConsoleApp

function compile() {
  javac $AppName.java
}

function execute() {
  java $AppName <<EOF
1 2
EOF
}

compile; execute;