module, requires, and exports are reserved keywords in module declarations and cannot be used as regular identifiers anywhere in Java code.

goto and const are reserved keywords and cannot be used as identifiers, although they are not currently used in Java.

• boolean: Represents true/false values
  
  
• char: Single 16-bit Unicode character
  
  
• byte: 8-bit signed integer (-128 to 127)
  
  
• short: 16-bit signed integer (-32,768 to 32,767)
  
  
• int: 32-bit signed integer (-2³¹ to 2³¹-1)
  
  
• long: 64-bit signed integer (-2⁶³ to 2⁶³-1)
  
  
• float: 32-bit floating point
  
  
• double: 64-bit floating point
  
  

• void: Indicates that a method doesn't return any value
  
  
• var: Local variable type inference (cannot be used for class/instance fields, method parameters, or return types)
  
  
• enum: Defines a fixed set of constants
  
  
• class: Declares a class
  
  
• interface: Declares an interface
  
  

• public: Accessible from anywhere
  
  
• private: Accessible only within the same class
  
  
• protected: Accessible within package and subclasses
  
  

• extends: Class inheritance (single inheritance)
  
  
• implements: Interface implementation (multiple inheritance of type)
  
  
• abstract: Declares abstract classes/methods (cannot be instantiated)
  
  
• final: Prevents inheritance (classes), overriding (methods), or reassignment (variables)
  
  

• new: Creates new object instances
  
  
• this: Reference to current object instance
  
  
• super: Reference to parent class
  
  
• instanceof: Tests object type at runtime
  
  

• static: Belongs to class rather than instance (shared among all objects)
  
  
• native: Method implemented in platform-specific code (JNI)
  
  
• volatile: Ensures variable visibility across threads (prevents caching)
  
  
• transient: Excludes field from serialization
  
  
• synchronized: Thread-safe method/block execution
  
  
• strictfp: Ensures consistent floating-point calculations across platforms
  
  

• if: Conditional execution
  
  
• else: Alternative execution path
  
  
• switch: Multi-way branching
  
  
• case: Individual switch cases
  
  
• default: Default case in switch statements
  
  

• for: Counter-controlled loop (traditional and enhanced for-each)
  
  
• while: Condition-controlled loop (pre-test)
  
  
• do: Condition-controlled loop (post-test)
  
  

• continue: Skips current iteration, continues with next
  
  
• break: Exits loops or switch statements
  
  
• return: Exits method and optionally returns value
  
  

• try: Defines block that may throw exceptions
  
  
• catch: Handles specific exception types
  
  
• finally: Always executes regardless of exceptions
  
  
• throw: Explicitly throws an exception
  
  
• throws: Declares exceptions that method may throw
  
  

• import: Imports classes/packages for use
  
  
• package: Declares a package namespace
  
  

• assert: Runtime assertions for debugging (must be enabled with -ea flag)