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533The Object Class and toString's Default Behavior
534Why toString Matters: Debugging and Logging
535Overriding toString: Basic Syntax
536Formatting toString Output: Best Practices
537toString for Complex Objects: Nested References
538StringBuilder for Efficient toString Implementations
539IDE-Generated toString Methods
540toString in Collections and Arrays
541The equals Method: Reference vs Logical Equality
542Overriding equals: The Five Requirements
543Implementing equals: The Step-by-Step Recipe
544The hashCode Method: What It Returns
545The equals-hashCode Contract: Core Requirement
546Why hashCode Matters for Hash-Based Collections
547Implementing hashCode: Combining Field Hash Codes
548Objects.equals and Objects.hash Utility Methods
549Common equals and hashCode Mistakes
550equals and hashCode with Inheritance
551The Cantor Principle: Why the Contract Is Not Bidirectional
552IDE Generation and Records: Automatic Implementation
553The HashMap Contract: equals and hashCode Must Agree
554How HashMap Uses hashCode for Bucket Selection
555Duplicate Keys with Broken hashCode: The Problem
556The Lookup Failure: Finding Keys That Exist
557Demonstrating the Bug: A Step-by-Step Example
558HashSet Breakage: The Same Root Cause
559The equals-hashCode Contract in Detail
560Fixing the Bug: Implementing Both Methods Correctly
561The Cloneable Interface and Object.clone
562Default clone Behavior: Shallow Copying
563Implementing clone: Overriding and CloneNotSupportedException
564Shallow Copy Problem: Shared References
565Deep Copying: Cloning Referenced Objects
566Deep Copy Example: Arrays and Collections
567Clone and Inheritance: Calling super.clone
568When Not to Use clone: Alternatives
569Final Fields and clone: The Conflict
570Clone Best Practices and Common Pitfalls
571The getClass Method: Runtime Type Information
572Using getClass for Type Comparison
573Class Objects and Reflection Entry Point
574The finalize Method: Legacy Cleanup Mechanism
575Problems with finalize: Unpredictability and Performance
576Modern Alternatives to finalize
577Deprecation of finalize in Java 9+

533The Object Class and toString's Default Behavior
534Why toString Matters: Debugging and Logging
535Overriding toString: Basic Syntax
536Formatting toString Output: Best Practices
537toString for Complex Objects: Nested References
538StringBuilder for Efficient toString Implementations
539IDE-Generated toString Methods
540toString in Collections and Arrays
541The equals Method: Reference vs Logical Equality
542Overriding equals: The Five Requirements
543Implementing equals: The Step-by-Step Recipe
544The hashCode Method: What It Returns
545The equals-hashCode Contract: Core Requirement
546Why hashCode Matters for Hash-Based Collections
547Implementing hashCode: Combining Field Hash Codes
548Objects.equals and Objects.hash Utility Methods
549Common equals and hashCode Mistakes
550equals and hashCode with Inheritance
551The Cantor Principle: Why the Contract Is Not Bidirectional
552IDE Generation and Records: Automatic Implementation
553The HashMap Contract: equals and hashCode Must Agree
554How HashMap Uses hashCode for Bucket Selection
555Duplicate Keys with Broken hashCode: The Problem
556The Lookup Failure: Finding Keys That Exist
557Demonstrating the Bug: A Step-by-Step Example
558HashSet Breakage: The Same Root Cause
559The equals-hashCode Contract in Detail
560Fixing the Bug: Implementing Both Methods Correctly
561The Cloneable Interface and Object.clone
562Default clone Behavior: Shallow Copying
563Implementing clone: Overriding and CloneNotSupportedException
564Shallow Copy Problem: Shared References
565Deep Copying: Cloning Referenced Objects
566Deep Copy Example: Arrays and Collections
567Clone and Inheritance: Calling super.clone
568When Not to Use clone: Alternatives
569Final Fields and clone: The Conflict
570Clone Best Practices and Common Pitfalls
571The getClass Method: Runtime Type Information
572Using getClass for Type Comparison
573Class Objects and Reflection Entry Point
574The finalize Method: Legacy Cleanup Mechanism
575Problems with finalize: Unpredictability and Performance
576Modern Alternatives to finalize
577Deprecation of finalize in Java 9+

Lesson 550 of 2,870·13. The Object Class and Common MethodsPro lesson

equals and hashCode with Inheritance

Understand why equals is dangerous to override in hierarchies and how getClass vs instanceof affects the symmetry requirement.

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