Example 1 - COBOL Calling Java Static Method

This example demonstrates a native COBOL program executing a Java static method.

When the COBOL program is run, it passes the Java program a string array that is processed by Java, and also makes a call to Java where the Java program returns an array which the COBOL program processes.

Important: For UNIX platforms, ensure that the current working folder and the folder containing libjvm.so is available on the LD_LIBRARY_PATH (or LIBPATH on AIX) environment variable.

Create the following Java file (Demo1.java):

import java.math.BigDecimal;
import java.util.Arrays;

public class Demo1
   {
    public static void static1(String[] d)
    {
        System.out.println("---Output from Java Demo1.static1 method---");
        for (int i = 0; i < d.length; i++)
        {
            System.out.println(d[i]);
        }
        Arrays.sort(d);
    }
    /* select colours from array */
    public static String[] static2(int[] s)
    {
        System.out.println("---Output from Java Demo1.static2 method---");
        for (int i: s)
            System.out.println(i);
        String[] rainbow = {"Red", "Orange", "Yellow", "Green", "Blue", "Indigo", "Violet"};
        String[] ret = {rainbow[s[0]], rainbow[s[1]], rainbow[s[2]], rainbow[s[3]], rainbow[s[4]]};
        return ret;
    }
}

Ensure that the current working folder is on the CLASSPATH (UNIX/Linux platforms only).
Compile Demo1.java:
```
javac Demo1.java
```
This produces a Demo1.class file in the current folder.

In the same folder, create the following COBOL file (demo1.cbl):

      $set sourceformat(variable) nsymbol(national)
       78 MAX_OCC value 5.
       01 i pic xxxx comp-5.
       01 grp2.
          03 nat1 pic n(10) national occurs MAX_OCC
                 value n"Red" n"Green" n"Blue" n"Orange" n"Indigo".
       01 grp3.
         03 utf1 pic u(10) occurs MAX_OCC.
       01 grp4.
         03 num2 pic xxxx comp-5 occurs MAX_OCC
                  value 1 2 4 5 6. 
       procedure division.
      *> Sort COBOL array
        call "java.Demo1.static1" using grp2
        display "---Output from COBOL---"
        perform varying i from 1 by 1 until i > 5
            display nat1(i)
        end-perform
      *> Select colours of the rainbow from input array
      *> Careful Java has 0 based array indexes
         call "java.Demo1.static2" using grp4 returning grp3
         display "---Output from COBOL---"
         perform varying i from 1 by 1 until i > 5
            display utf1(i)
         end-perform.

Compile and link the COBOL file:
Windows:
```
cobol demo1.cbl; 
cbllink demo1.obj
```
UNIX:
```
cob -x demo1.cbl  
```
This produces the final COBOL executable file, demo1.exe (Windows) or demo1 (UNIX).
Run the executable file:
Windows:
```
demo1.exe
```
UNIX:
```
./demo1
```
The program output, showing output from both the COBOL program and Java program, should look like this:
```
---Output from Java Demo1.static1 method---
Red
Green
Blue
Orange
Indigo
---Output from COBOL---
Blue
Green
Indigo
Orange
Red
---Output from Java Demo1.static2 method---
1
2
4
5
6
---Output from COBOL---
Orange
Yellow
Blue
Indigo
Violet
```
The code and the output shows the COBOL code executing the static1 method, processing some COBOL operations, then executing the static2 method, and processing some more COBOL operations.