For the Java Control API version that requires Java SE 11 or above, here are the classes and interfaces with brief descriptions:

[detail level 12345]

▼Pcom
▼Pgams	Provides package namespace for Java interface and examples to General Algebraic Model System (GAMS)
▼Papi	Provides a Java programming interface to the General Algebraic Model System (GAMS)
►CAbstractRunParameters	Abstract class for run parameters
CnewBuilder	Abstract builder of AbstractRunParameters
CGAMSCheckpoint	An instance of `GAMSCheckpoint` captures the state of a `GAMSJob` after the `GAMSJob.run` method has been carried out, and can be created via the call of `GAMSWorkspace.addCheckpoint methods`
CGAMSDatabase
CGAMSDatabaseDomainViolation	An instance of `GAMSDatabaseDomainViolation` stores a domain violation information for each symbol in a `GAMSDatabase` instance
CGAMSDatabaseIterator	An iterator of a `GAMSDatabase` over a collection of `GAMSSymbol`
CGAMSEngineConfiguration	Configuration that allows the execution of jobs on a specific GAMS Engine instance
►CGAMSEngineJob	GAMSEngineJob manages the execution of a GAMS program given by GAMS model source for GAMS Engine
CnewBuilder	A builder of GAMSEngineJob
►CGAMSEngineRunParameters	Run parameters for GAMSEngineJob
CnewBuilder	A builder of GAMSEngineRunParameters
CGAMSEquation	This is the representation of an equation symbol in GAMS
CGAMSEquationRecord	This is the representation of a single record of a `GAMSEquation` instance
CGAMSException	`GAMSException` contains the information described the cause of exception during the execution of GAMS Java API
CGAMSExecutionException	`GAMSExecutionException` contains the exit code unsuccessfully returned by GAMS process
►CGAMSGlobals	GAMSGlobals defines constants that are used by com.gams.api package
CArchType	GAMS enumerated type of architecture
CAttributeValue	Atttribute Values as enumerated integer
CDataType	GAMS Data Types
CDebugLevel	Define GAMS Debug Level of different values and string representations
CEquType	Equation SubType
CExitCodeMessage	The possible return codes of the GAMS compiler and execution system (cmexRC)
CModelStat	Model Solution Status
COSType	GAMS enumerated type of operating system
CSetType	Set SubType
CSolveStat	Solver termination condition
CSpecialValues	Special GAMS Values used by GAMS Java API
CSpecialValues_int	Special GAMS Value as enumerated integer
CUpdateAction	What field to update
CVarType	Variable SubType
CGAMSJob
►CGAMSModelInstance
CSymbolUpdateType	GAMS Symbol update type
CGAMSModelInstanceOpt	The `GAMSModelInstanceOpt` can be used to customize the `GAMSModelInstance`.solve() routine
CGAMSModifier	Instances of this class are input to `GAMSModelInstance.instantiate` method
►CGAMSOptions
CEAction	GAMS processing request
CEAppendExpand	Expand file append option
CEAppendOut	Output file append option
CEAsyncSolLst	Print solution listing when asynchronous solve (Grid or Threads) is used
CECaptureModelInstance	Switch to capture all model instances within a run
CECase	Output case option for LST file
CECharSet	Character set flag
CECheckErrorLevel	Check errorLevel automatically after executing external program
CEDFormat	Date format
CEDigit	Switch default for "$on/offDigit"
CEDumpOpt	Writes preprocessed input to the file input.dmp
CEDumpParms	GAMS parameter logging
CEECImplicitLoad	Allow implicit loading of symbols from embedded code or not
CEECLogLine	Show log line about embedded code initialization and execution or not
CEEmpty	Switch default for "$on/offEmpty"
CEErrMsg	Placing of compilation error messages
CEExecMode	Limits on external programs that are allowed to be executed
CEFDOpt	Options for finite differences
CEFileCase	Casing of file names and paths (put, gdx, ref, $include, etc.)
CEFiltered	Switch between filtered and domain-checked read from GDX
CEForceWork	Force GAMS to process a save file created with a newer GAMS version or with execution errors
CEFreeEmbeddedPython	Free external resources at the end of each embedded Python code blocks
CEgdxCompress	Compression of generated GDX file
CEgdxConvert	Version of GDX files generated (for backward compatibility)
CEgdxUels	Unload labels or UELs to GDX either squeezed or full
CEHoldFixed	Treat fixed variables as constants
CEHoldFixedAsync	Allow HoldFixed for models solved asynchronously as well
CEImplicitAssign	Switch default for "$on/offImplicitAssign"
CEInteractiveSolver	Allow solver to interact via command line input
CEIntVarUp	Set mode for default upper bounds on integer variables
CEKeep	Controls keeping or deletion of process directory and scratch files
CEListing	Switch default for "$on/offListing"
CELogLine	Amount of line tracing to the log file
CELstTitleLeftAligned	Write title of LST file all left aligned
CEMemoryManager	Allows to try an experimental memory manager
CEMIIMode	Model Instance Mode
CENoNewVarEqu	Triggers a compilation error when new equations or variable symbols are introduced
CEOn115	Generate errors for unknown unique element in an equation
CEPageContr	Output file page control option
CEPrefixLoadPath	Prepend GAMS system directory to library load path
CEPreviousWork	Indicator for writing workfile with previous workfile version
CEProcTreeMemMonitor	Monitor the memory used by the GAMS process tree
CEPutNR	Numeric round format for put files
CEReferenceLineNo	Controls the line numbers written to a reference file
CEReplace	Switch between merge and replace when reading from GDX into non-empty symbol
CERequestMarginals	Request marginals from the solver
CESavePoint	Save solver point in GDX file
CEShowOSMemory	Show the memory usage reported by the Operating System instead of the internal counting
CESolPrint	Solution report print option
CESolveLink	Solver link option
CESolveOpt	Multiple solve management
CEStepSum	Summary of computing resources used by job steps
CEstrictSingleton	Error if assignment to singleton set has multiple elements
CEStringChk	String substitution options
CESuffixAlgebraVars	Switch default for "$on/offSuffixAlgebraVars"
CESuffixDLVars	Switch default for "$on/offSuffixDLVars"
CESuppress	Compiler listing option
CESys10	Changes rpower to ipower when the exponent is constant and within 1e-12 of an integer
CESys11	Dynamic resorting if indices in assignment/data statements are not in natural order
CESysOut	Solver Status file reporting option
CETFormat	Time format
CETraceOpt	Trace file format option
CEZeroResRep	Report underflow as a warning when abs(results) LE ZeroRes and result set to zero
CGAMSParameter	This is the representation of a parameter symbol in GAMS
CGAMSParameterRecord	This is the representation of a single record of a `GAMSParameter` instance
►CGAMSRunParameters	Run parameters for GAMSJob
CnewBuilder	A builder of GAMSRunParameters
CGAMSSet	This is the representation of a set symbol in GAMS
CGAMSSetRecord	This is the representation of a single record of a `GAMSSet` instance
CGAMSSymbol	This is the representation of a symbol in GAMS
CGAMSSymbolDomainViolation	An instance of `GAMSSymbolDomainViolation` stores a domain violation information for a `GAMSSymbol` instance
CGAMSSymbolIterator	An iterator of a GAMSymbol over a collection of GAMSSymbolRecord
CGAMSSymbolRecord	This is the representation of a single record of a `GAMSSymbol` instance
CGAMSVariable	This is the representation of a variable symbol in GAMS
CGAMSVariableRecord	This is the representation of a single record of a `GAMSVariable` instance
CGAMSWorkspace
CGAMSWorkspaceInfo
CResourceType	The ResourceType defines all resource types