Java `this` Keyword: Distinguish Variables, Quick Mastery
In Java, the `this` keyword refers to a reference of the current object, and its core functions are to resolve variable conflicts, reuse constructor methods, and simplify object operations. 1. **Resolving Variable Conflicts**: When a method's local variable has the same name as a member variable, use `this.` to explicitly access the member variable (e.g., `this.name`), avoiding the local variable from overriding the member variable. 2. **Calling Other Constructors**: Use `this(parameters)` to call another constructor of the same class on the first line of a constructor, avoiding code duplication (only one call is allowed per constructor). 3. **Implementing Method Chaining**: Return `this` within a method (e.g., in setter methods like `setName()`), enabling chained calls (e.g., `obj.setName().setAge().show()`). **Note**: `this` cannot be used in static methods (no object context exists), and `this` is an immutable reference. Proper use of `this` can make code more concise and structured.
Read MoreJava Inheritance Syntax: How Subclasses Inherit from Parent Classes and Understanding the Inheritance Relationship Simply
This article explains Java inheritance, with the core being subclasses reusing parent class attributes and methods while extending them, implemented via the `extends` keyword. The parent class defines common characteristics (attributes/methods), and subclasses can add unique functionalities after inheritance, satisfying the "is - a" relationship (the subclass is a type of the parent class). Subclasses can inherit non - `private` attributes/methods from the parent class; `private` members need to be accessed through the parent class's `public` methods. Subclasses can override the parent class's methods (keeping the signature unchanged) and use `super` to call the parent class's members or constructors (with `super()` in the constructor needing to be placed on the first line). The advantages of inheritance include code reuse, strong scalability, and clear structure. Attention should be paid to the single inheritance restriction, the access rules for `private` members, and the method overriding rules.
Read MoreJava Classes and Objects: From Definition to Instantiation, the Basics of Object-Oriented Programming
The core of Object-Oriented Programming (OOP) is to abstract real-world entities into "classes" (object templates containing attributes and methods), and then simulate operations through "objects". A class like `Person` includes attributes such as `name` and `age`, and a method like `sayHello`. Objects are created using the `new` keyword (e.g., `Person person = new Person()`), and members are accessed using the `.` operator (for assignment or method calls). Constructor methods can initialize attributes (e.g., `Person(String name, int age)`). It is important to follow naming conventions (class names start with a capital letter, members with lowercase), default values, object independence, and encapsulation (member variables are recommended to be `private` and accessed via `getter/setter` methods). Mastering classes and objects is fundamental for subsequent learning of encapsulation, inheritance, and polymorphism.
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