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This article is about the difference between override and overload in Java. The editor thinks it is very practical, so share it with you as a reference and follow the editor to have a look.

Java::override vs overload

Java grammar is so delicate that it attracts countless heroes to bend over.

(1) override:

Class Parent {

Object func (Number n) {

...

}

}

Class Child extends Parent {

Object func (Number n) {

...

}

}

This is so-called override.

The meaning of override is commonly known as "polymorphism".

Child.func and Parent.func can be seen as occupying the same Entry in the virtual function pointer table. That is, Child.func covers Parent.func.

Parent vtable

Entry 1:Parent.func

Child vtable

Entry 1:Child func

Override is the program run-time dynamic decision which method to call, so it is called: polymorphism.

(2) overload

Class Child {

Object func (Number n) {

...

}

Object func (String s) {

...

}

}

This is so-called overload.

Note: two func methods have the same name, but the parameters are different, so they are completely different methods. These two func methods occupy two different Entry in the virtual function pointer table.

Vtable

Void func (Number)

Void func (String)

Attention:

When overload compiles, it decides which method to call. The compiler generates JVM instructions with different calling function addresses (different Entry) according to different parameter types.

How to translate BTW:overload into overload? I really don't understand. Overload means overload in English. I strongly doubt that the word "overload" is a coined word, like Alpine White. It can only be understood, but it cannot be put into words.

(3)

Class Parent {

Object func (Number n) {

...

}

}

Class Child extends Parent {

Object func (String s) {

...

}

}

This is also overload.

Parent vtable

Entry 1:void func (Number n) of parent

Child vtable

Entry 1:void func (Number n) of parent

Entry 2:void func (String s) of child

(4)

Class Parent {

Object func (Number n) {

...

}

}

Class Child extends Parent {

Object func (Number n) {

...

}

Object func (String s) {

...

}

}

This example code has both override and overload.

Parent vtable

Entry 1:void func (Number n) of parent

Child vtable

Entry 1:void func (Number n) of child

Entry 2:void func (String s) of child

= > Conclusion:

A:Strongly advise to avoid using "overload".

B:Strongly advise to use different method names.

For instance:

Objcet funcNumber (Number n) {

...

}

Object funcString (String s) {

...

}

End.

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