[可见度] interface 接口名称 [extends 其他的接口名] {

        // 声明变量

        // 抽象方法

}

import java.lang.*;

//引入包

public interface NameOfInterface

{

   //任何类型 final, static 字段

   //抽象方法

}

interface Animal {

   public void eat();

   public void travel();

}

public class MammalInt implements Animal{

   public void eat(){

      System.out.println("Mammal eats");

   }

   public void travel(){

      System.out.println("Mammal travels");

   } 

   public int noOfLegs(){

      return 0;

   }

   public static void main(String args[]){

      MammalInt m = new MammalInt();

      m.eat();

      m.travel();

   }

}

public interface Sports

{

   public void setHomeTeam(String name);

   public void setVisitingTeam(String name);

}

// 文件名: Football.java

public interface Football extends Sports

{

   public void homeTeamScored(int points);

   public void visitingTeamScored(int points);

   public void endOfQuarter(int quarter);

}

// 文件名: Hockey.java

public interface Hockey extends Sports

{

   public void homeGoalScored();

   public void visitingGoalScored();

   public void endOfPeriod(int period);

   public void overtimePeriod(int ot);

}

public interface Hockey extends Sports, Event

package java.util;

public interface EventListener

{}