接口的声明与使用

computable.java

public interface computable {int MAX=100;int f(int x);}

china.java

public class china implements computable{int number;public int f(int x){int sum=0;for(int i=1;i<=x;i++){sum=sum+i;}return sum;}}

Japan.java

public class Japan implements computable{int number;public int f(int x){return 66+x;}}

test.java

public class test {public static void main(String args[]){china zhang;Japan henlu;zhang=new china();henlu=new Japan();zhang.number=991898+computable.MAX;henlu.number=941448+computable.MAX;    System.out.println("number:"+zhang.number+"求和"+zhang.f(100));    System.out.println("number:"+henlu.number+"求和"+henlu.f(100));}}