Byte arrays and general group parameters

For any groups that do not meet the definition of a Java-compatible array type, the COBOL compiler assumes that you want to treat the group as a flat array of bytes in Java (byte[]) and that the Java code will extract data from the byte array or write data to the byte array in a way that matches the layout of the data in COBOL. For details about Java-compatible array types, see the Table: Java-compatible array COBOL types in the Enterprise COBOL for z/OS® Language Reference.

For example, consider the following COBOL group:

01 g1.
  03 g1-data1 pic s9(9) comp-5 value 12.
  03 g1-data2 pic s9(18) comp-5 value 15.

This group will be identified by the compiler as corresponding to an array of bytes in Java. If g1 is used as a parameter in a COBOL program with the JAVA-CALLABLE directive, then it is assumed that the incoming data from Java is in a byte array (byte[]) and it is the Java program's responsibility to set up the array correctly.

Meanwhile, if the COBOL program passes g1 as an argument in a CALL to a static Java method, the corresponding Java method must receive the group as an array of bytes.

Here is an example of a static Java method that can be called from COBOL and can receive group argument g1 as a byte array and access the two subordinate data items of g1:

import java.nio.*;

public class TestApp
{
  public static void myMethod(byte[] g1)
  {
    ByteBuffer bb = ByteBuffer.wrap(g1, 0, 12);
    System.out.println("data1 = " + bb.getInt(0));
    System.out.println("data2 = " + bb.getLong(4));
  }
}