1. Interface Definition Language
In Java we cannot separate a class’s definition from its implementations as we can in C++
Header files
Implementation files
CORBA allows the separation of definition and implementation
CORBA uses IDL for defining interfaces between clients and servers
ORB Vendors provide specific IDL compilers for supported languages
create target language stubs and skeletonsfor building CORBA clients and servers
C, C++, Smalltalk, Java, COBOL …

2. IDL/Java type mapping
due to differences in heritage IDL and Java types don’t have a 1 to 1 mapping:
long Java int
short Java short
float Java float
double Java double
char Java char
boolean Java boolean
octet java byte
string java.lang.String
any Special type consisting of any of the above

3. an IDL interface ex. interface Cooler { int getHotWaterLevel();
int getWarnWaterLevel();
int getColdWaterLevel();
exception NoMoreWaterException { };
int getHotWater() throws NoMoreWaterException;
int getWarmWater() throws NoMoreWaterException;
int getColdWater() throws NoMoreWaterException; }

4. Compiling the IDL
Compiling the IDL using the javatoidl compiler will produce six classes:
CoolerRef
CoolerHolder
CoolerOperations
CoolerStub
CoolerServant
CoolerSkeleton