java - Java中接口和类之间的契约

Question

这在 Java 中究竟意味着什么？

接口定义了实现类的契约

Answer 1

这意味着通过实现接口，类同意实现接口指定的所有功能。

Answer 2

In interface you simply declare the members(say methods). For example

public Interface Product{

protected void getProduct();
protected void getProductId();
}

Whereas in a class you can implement the above interface and can define these methods...

public class ProductClass implements Product{

protected void getProduct()
{
    System.out.println("Product is: ");
}
protected void getProductId()
{
    System.out.println("Product Id is: ");
}
}

So you can see the methods declared in interface are defined in the class. Basically, you can say that interface just provides the blueprint but class actually does the whole work.