方法重載和重寫(xiě)的核心區(qū)別在於：重載是在同一類中通過(guò)不同參數(shù)列表實(shí)現(xiàn)同名方法，而重寫(xiě)是子類重新定義父類的方法。具體來(lái)說(shuō)：1. 方法重載要求方法名相同但參數(shù)不同（數(shù)量、類型或順序），用於提升代碼可讀性和靈活性，如Calculator類中的add方法；2. 方法重寫(xiě)要求方法名、參數(shù)及返回類型完全一致，用於實(shí)現(xiàn)運(yùn)行時(shí)多態(tài)，如Dog類重寫(xiě)Animal的sound方法；3. 重載屬於編譯時(shí)多態(tài)，而重寫(xiě)屬於運(yùn)行時(shí)多態(tài)；4. 重載可用於靜態(tài)方法，而重寫(xiě)僅適用於實(shí)例方法。

Method overloading and overriding are two core concepts in Java related to polymorphism, but they serve different purposes and work in different ways.

What's the main difference?

Overloading happens when multiple methods in the same class share the same name but have different parameters (either in number, type, or order).
Overriding occurs when a subclass provides a specific implementation of a method that is already defined in its superclass.

Now let's break down each one with practical examples and use cases.

Method Overloading – Same name, different parameters

Overloading lets you define multiple methods with the same name but different input parameters. It helps make code cleaner and more readable by allowing flexibility in how a method can be called.

When do you use it?

You'll see this often in utility classes or APIs where a function should behave differently depending on what inputs are given.

For example:

 class Calculator {
    int add(int a, int b) {
        return ab;
    }

    double add(double a, double b) {
        return ab;
    }

    int add(int a, int b, int c) {
        return abc;
    }
}

Here, add is overloaded:

• One version takes two integers.
• Another takes two doubles.
• And another takes three integers.

Key points:

• Must change the method signature (number, type, or order of parameters).
• Return type alone doesn't matter — you can't overload just by changing return type.
• Access modifiers or exceptions don't affect overloading either.

Method Overriding – Subclass redefines behavior

Overriding allows a subclass to provide a new implementation for a method inherited from a superclass. This is key for runtime polymorphism in Java.

How does it work?

Let's say we have a base class Animal and a subclass Dog .

 class Animal {
    void sound() {
        System.out.println("Animal makes a sound");
    }
}

class Dog extends Animal {
    @Override
    void sound() {
        System.out.println("Dog barks");
    }
}

When you call sound() on an object of type Dog , the overridden version runs instead of the one in Animal .

Important rules:

• The method name, return type, and parameters must match exactly .
• The access level can't be more restrictive than the overridden method (eg, can't go from protected to private ).
• Static methods can't be overridden — they can only be hidden.
• Constructors cannot be overridden either.

A common place you'll see this is in GUI event handling or when working with frameworks like Spring or Android, where you're expected to override certain methods to customize behavior.

A few easy things to remember

• Overloading is compile-time polymorphism; overriding is runtime.
• Overloading is within the same class; overriding happens between parent and child classes.
• You can overload any method (including static ones), but you can only override instance methods.
• Use @Override annotation when overriding — it helps catch mistakes early.

So if you're writing Java code and wondering whether to overload or override, think:
Are you working inside the same class and varying input? → Use overloading.
Are you customizing a method from a parent class? → Use overriding.

基本上就這些.

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