[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
{}