接口和扩展

Question

在如何使用以下代码或什至可能时遇到问题。 我是新来的。 我有以下内容：

variables.java

public interface variables extends library{
     public int func1(String a, String b);
     public int func2(String a, String b); 
}

CallVariables.java

public CallVariables extends variables{
    String hi = "Hi";
    String by = "Bye";
    //Then here somehow call my variables.java and be able to use it...
}

ma​​in.java

// Now, here I want to be able to actually call the first or either the second .java class.
// Is this possible? If yes, then how? 

我想知道这是否可能，如果可以，请提供示例。

Answer 1

通过指定关键字“interface”来声明接口。例如：

interface MyInterface
{
   /* All the methods are public abstract by default
    * As you see they have no body
    */
   public void method1();
   public void method2();
}

Java 接口示例

这就是类实现接口的方式。它必须提供接口中声明的所有方法的主体，或者可以说类必须实现接口的所有方法。

一个类实现了接口，但一个接口扩展了另一个接口。

interface MyInterface
{
   /* compiler will treat them as: 
    * public abstract void method1();
    * public abstract void method2();
    */
   public void method1();
   public void method2();
}
class Demo implements MyInterface
{
   /* This class must have to implement both the abstract methods
    * else you will get compilation error
    */
   public void method1()
   {
    System.out.println("implementation of method1");
   }
   public void method2()
   {
    System.out.println("implementation of method2");
   }
   public static void main(String arg[])
   {
    MyInterface obj = new Demo();
    obj.method1();
   }
}

输出：

implementation of method1

我希望这可以更清楚地说明类如何与接口一起使用。

Answer 2

请遵循接口和类的命名约定。 类可以实现接口，接口可以扩展另一个接口，类可以扩展一个类。 这可能会对您有所帮助：

interface Library{}
//First variables.java:
     interface Variables extends Library{
         public int func1(String a, String b);
         public int func2(String a, String b); 
    }

//Second call Variables.java
     class CallVariables implements Variables{
         String hi = "Hi";
         String by = "Bye";
         //Then here somehow call my variables.java and be able to use it...
        @Override
        public int func1(String a, String b) {
            // TODO Auto-generated method stub
            System.out.println("func1 says :"+hi);
            return 1;
        }
        @Override
        public int func2(String a, String b) {
            // TODO Auto-generated method stub
            System.out.println("func2 says :"+by);
            return 2;
        }
     }
//Third main.java
     //Now, here I want to be able to actually call the first or either the second .java class. 
    // Is this possible? If yes, then how? 
     public class Main{
        public static void main(String[] args) {
            Variables variables = new CallVariables();
            variables.func1("a", "b");
            variables.func2("c", "d");
        }
     }