Interoperable data types for OO COBOL and Java

A subset of COBOL data types can be used for interoperation between OO COBOL and Java™.

Note: This section provides information about COBOL/Java data type compatibility for OO COBOL programs. For information about COBOL/Java data type compatibility for non-OO COBOL/Java interoperability, see Mapping between COBOL and Java data types for non-OO COBOL/Java interoperability.

You can specify the interoperable data types as arguments in COBOL INVOKE statements and as the RETURNING item in COBOL INVOKE statements. Similarly, you can pass these types as arguments from a Java method invocation expression and receive them as parameters in the USING phrase or as the RETURNING item in the PROCEDURE DIVISION header of a COBOL method.

The following table lists the primitive Java types and the COBOL data types that are supported for interoperation and the correspondence between them.

Table 1. Interoperable Java and COBOL data types
Java data type COBOL data type
boolean1 Conditional variable and two condition-names of the form: 
level-number  data-name        PIC X.
88            data-name-false  VALUE X'00'.
88            data-name-true   VALUE X'01' THROUGH X'FF'.
byte Single-byte alphanumeric, PIC X or PIC A
short USAGE BINARY, COMP, COMP-4, or COMP-5, with a PICTURE clause of the form S9(n), where 1 <= n <= 4
int USAGE BINARY, COMP, COMP-4, or COMP-5, with a PICTURE clause of the form S9(n), where 5 <= n <= 9
long USAGE BINARY, COMP, COMP-4, or COMP-5, with a PICTURE clause of the form S9(n), where 10 <= n <= 18
float2 USAGE COMP-1
double2 USAGE COMP-2
char
Single-character national: PIC N USAGE NATIONAL
(an elementary data item of category national)
class types
(object references)
 USAGE OBJECT REFERENCE class-name
  1. Enterprise COBOL interprets a PIC X argument or parameter as the Java boolean type only when the PIC X data item is followed by exactly two condition-names of the form shown. In all other cases, a PIC X argument or parameter is interpreted as the Java byte type.
  2. Java floating-point data is represented in IEEE binary floating-point, while Enterprise COBOL uses the IBM® hexadecimal floating-point representation. The representations are automatically converted as necessary when Java methods are invoked from COBOL and when COBOL methods are invoked from Java.

In addition to the primitive types, Java Strings and arrays of Java primitive types can interoperate with COBOL. This requires specialized mechanisms provided by the COBOL runtime system and the Java Native Interface (JNI).

In a Java program, to pass array data to COBOL or to receive array data from COBOL, you declare the array types using the usual Java syntax. In the COBOL program, you declare the array as an object reference that contains an instance of one of the special classes provided for array support. Conversion between the Java and COBOL types is automatic at the time of method invocation.

In a Java program, to pass String data to COBOL or to receive String data from COBOL, you declare the array types using the usual Java syntax. In the COBOL program, you declare the String as an object reference that contains an instance of the special jstring class. Conversion between the Java and COBOL types is automatic at the time of method invocation. The following table lists the Java array and String data types and the corresponding special COBOL data types.

Table 2. Interoperable COBOL and Java array and String data types
Java data type COBOL data type
boolean[ ] object reference jboooleanArray
byte[ ] object reference jbyteArray
short[ ] object reference jshortArray
int[ ] object reference jintArray
long[ ] object reference jlongArray
char[ ] object reference jcharArray
Object[ ] object reference jobjectArray
String object reference jstring

The following java array types are not currently supported:

Java data type COBOL data type
float[ ] object reference jfloatArray
double[ ] object reference jdoubleArray

You must code an entry in the repository paragraph for each special class that you want to use, just as you do for other classes. For example, to use jstring, code the following entry:


Configuration Section.
Repository.
    Class jstring is "jstring".

Alternatively, for the String type, the COBOL repository entry can specify an external class name of java.lang.String:


Repository.
    Class jstring is "java.lang.String".

Callable services are provided by the Java Native Interface (JNI) for manipulating the COBOL objects of these types in COBOL. For example, callable services can be used to set COBOL alphanumeric or national data into a jstring object or to extract data from a jstring object. For details on use of JNI callable services for these and other purposes, see Accessing JNI services in the Enterprise COBOL Programming Guide.

For details on repository entries for class definitions, see REPOSITORY paragraph. For examples, see External class-names and Java packages in the Enterprise COBOL Programming Guide.