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Java

855What Are Generics and Why They Matter
856Declaring a Generic Class with a Single Type Parameter
857Type Parameters: Naming Conventions (T, E, K, V)
858Instantiating Generic Classes with Type Arguments
859Diamond Operator: Type Inference in Constructors
860Multiple Type Parameters in a Single Class
861Type Parameters in Fields, Methods, and Constructors
862Type Parameter Scope: Class-Level vs Method-Level
863Generic Constructors and Constructor Invocations
864Restrictions: Cannot Instantiate Type Parameters with new T()
865What Are Generic Methods?
866Declaring Generic Methods: Type Parameter Syntax
867Type Inference in Generic Method Calls
868Multiple Type Parameters in Methods
869Generic Methods in Non-Generic Classes
870Generic Static Methods: Utility Method Patterns
871Explicit Type Arguments: The Diamond Before the Method
872Generic Constructors
873Common Pitfalls: Type Parameter Shadowing
874Creating Instances of Generic Classes
875The Diamond Operator (<>)
876Type Arguments Cannot Be Primitives
877Generic Array Creation Restrictions
878Static Context and Type Parameters
879Nested Generic Types
880Constructor Type Inference
881Parameterized Types as Type Arguments
882What Are Raw Types?
883Raw Type Syntax and Declaration
884Type Safety Loss with Raw Types
885Compiler Warnings: Unchecked Operations
886Interoperating with Pre-Generics Code
887Raw Types vs Unbounded Wildcards
888Heap Pollution from Raw Types
889Migrating Legacy Code to Generics
890When Raw Types Are Unavoidable
891What Is Type Erasure?
892Why Type Erasure Exists
893Type Parameters Become Object
894Bounded Type Parameters Become Their Bound
895Bridge Methods for Type Safety
896No Generic Type Information at Runtime
897Cannot Create Generic Arrays
898Type Tokens and Reification Workarounds
899Heap Pollution from Raw Types
900ArrayList<E> as the Canonical Generic Collection
901Creating ArrayList with Type Arguments
902Type Safety: Compile-Time vs Runtime
903Adding and Retrieving Elements Without Casting
904Autoboxing with Generic Collections
905The Diamond Operator: Type Inference
906Generic Collection Methods: forEach and Enhanced for
907LinkedList<E> and Other Generic List Implementations
908HashSet<E> and HashMap<K,V>: Multiple Type Parameters
909Collections of Collections: Nested Generics

Java

855What Are Generics and Why They Matter
856Declaring a Generic Class with a Single Type Parameter
857Type Parameters: Naming Conventions (T, E, K, V)
858Instantiating Generic Classes with Type Arguments
859Diamond Operator: Type Inference in Constructors
860Multiple Type Parameters in a Single Class
861Type Parameters in Fields, Methods, and Constructors
862Type Parameter Scope: Class-Level vs Method-Level
863Generic Constructors and Constructor Invocations
864Restrictions: Cannot Instantiate Type Parameters with new T()
865What Are Generic Methods?
866Declaring Generic Methods: Type Parameter Syntax
867Type Inference in Generic Method Calls
868Multiple Type Parameters in Methods
869Generic Methods in Non-Generic Classes
870Generic Static Methods: Utility Method Patterns
871Explicit Type Arguments: The Diamond Before the Method
872Generic Constructors
873Common Pitfalls: Type Parameter Shadowing
874Creating Instances of Generic Classes
875The Diamond Operator (<>)
876Type Arguments Cannot Be Primitives
877Generic Array Creation Restrictions
878Static Context and Type Parameters
879Nested Generic Types
880Constructor Type Inference
881Parameterized Types as Type Arguments
882What Are Raw Types?
883Raw Type Syntax and Declaration
884Type Safety Loss with Raw Types
885Compiler Warnings: Unchecked Operations
886Interoperating with Pre-Generics Code
887Raw Types vs Unbounded Wildcards
888Heap Pollution from Raw Types
889Migrating Legacy Code to Generics
890When Raw Types Are Unavoidable
891What Is Type Erasure?
892Why Type Erasure Exists
893Type Parameters Become Object
894Bounded Type Parameters Become Their Bound
895Bridge Methods for Type Safety
896No Generic Type Information at Runtime
897Cannot Create Generic Arrays
898Type Tokens and Reification Workarounds
899Heap Pollution from Raw Types
900ArrayList<E> as the Canonical Generic Collection
901Creating ArrayList with Type Arguments
902Type Safety: Compile-Time vs Runtime
903Adding and Retrieving Elements Without Casting
904Autoboxing with Generic Collections
905The Diamond Operator: Type Inference
906Generic Collection Methods: forEach and Enhanced for
907LinkedList<E> and Other Generic List Implementations
908HashSet<E> and HashMap<K,V>: Multiple Type Parameters
909Collections of Collections: Nested Generics

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Lesson 864 of 2,870·21. Generics FundamentalsPro lesson

Restrictions: Cannot Instantiate Type Parameters with new T()

Learn why new T() is illegal due to type erasure and how to work around it.

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