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javainterfaceabstract-class
Hawii Hawii
Hawii Hawii

Reputation: 157

Java multiple interfaces implementation

the setting is like this.
I have multiple interfaces (i.e. A,B,C) and I have classes (Z and Y) to implements them
X implements A,B{} and Y implements A,C{} and Z implements B,C{}

Some functions in interface A,B,C have the same definition and I don't want to retype them in each class, how should I do?
I did google it, and notice that one solution is to use a handy keyword default in the interface. But what if I am prohibited from using this keyword, like the code is compatible with version prior than Java8?

Is there a better way to handle this problem?

Upvotes: 1

Views: 847

Answers (2)

Saurabh Oza
Saurabh Oza

Reputation: 179

Then you should go with abstract class and provide some default implementation for the common methods in different interfaces as below.

interface A {
    void m1();
    void common();
}

interface B {
    void m2();
    void common();
}

abstract class ABClass implements A, B {

    public void common() {
    System.out.println("Default");
}

Class X extends ABClass {
}

Upvotes: 1

GAdams
GAdams

Reputation: 266

Instead of gaining these methods through inheritance and having to extend mutliple classes to get your definitions in, you could favor composition and take a class that implements the method you want to reuse as a parameter. Keeping it as a private final member variable, you can call this common method in a generic way.

Upvotes: 1

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