java-mapping

name	java-mapping
description	Mappings from COBOL constructs to Java equivalents. Covers data type mappings, control flow mappings, file I/O patterns, and Spring Boot architecture recommendations. Use when migration-advisor is producing Java blueprints for COBOL programs.

COBOL → Java Mapping Reference

Data Type Mappings

COBOL PIC	Java Type	Notes
PIC 9(1-4)	int	Small integers
PIC 9(5-9)	long	Larger integers
PIC 9(10+)	BigInteger	Very large integers
PIC 9(n)V9(m)	BigDecimal	Always use BigDecimal for money
PIC S9(n)V9(m)	BigDecimal	Signed decimal
PIC X(n)	String	Use .trim() when reading COBOL data
PIC A(n)	String	Alphabetic — still String in Java
01-level group	POJO / Java Record	Field-per-child mapping
88-level condition	boolean / enum constant	if (ws.customerActive)
OCCURS n TIMES	T[] or List	Prefer List for mutability
OCCURS DEPENDING ON	List (dynamic)	Size from the depending-on field

Control Flow Mappings

COBOL Construct	Java Equivalent
PERFORM para-name	privateMethod() call
PERFORM para VARYING x FROM 1 BY 1 UNTIL x > n	for (int x = 1; x <= n; x++)
PERFORM para UNTIL condition	while (!condition) { method(); }
EVALUATE TRUE WHEN cond1	if/else if chain or switch expression
EVALUATE var WHEN val1	switch(var) { case val1: }
GOTO (simple)	Extract to loop or if/else
GOTO (complex)	State machine pattern
ALTER	Manual refactor required — no mapping
STOP RUN	return; (from main method)

File I/O Mappings

COBOL Pattern	Java/Spring Pattern
OPEN INPUT file	repository.findAll() or FileReader
READ file AT END	Iterator hasNext() check
WRITE record	repository.save(entity)
CLOSE file	(handled by Spring / try-with-resources)
Sequential file processing	Spring Batch ItemReader/ItemWriter
VSAM KSDS (keyed)	Spring Data JPA with @Id

Program Type → Spring Boot Architecture

COBOL Program Type	Spring Component	Pattern
Batch program (file in/out)	@Configuration + ItemProcessor	Spring Batch Job
Subroutine (LINKAGE SECTION)	@Service	Injected service bean
CICS transaction	@RestController	REST endpoint
Report generator	@Service + @Component	Service + template
DB2 embedded SQL	@Repository + JPA	Spring Data JPA

Copybook → Shared Domain Object

Each copybook becomes a shared Java class in a common or domain module:

// COBOL: CUSTOMER-RECORD copybook
// Java:
public record CustomerRecord(
    long customerId,      // PIC 9(8)
    String customerName,  // PIC X(40) — trim() on construction
    BigDecimal balance,   // PIC S9(9)V99
    boolean isActive      // 88 CUSTOMER-ACTIVE VALUE 'Y'
) {}

For full type mapping tables: read TYPE-MAPPING.md

For structural pattern mappings: read PATTERN-MAPPING.md