interfacedemo.java

这是java 2应用开发指南这本书上所有例子的源代码

//interfaceDemo.java
interface one{
        double A=30.0;
        void add(int n);
        void subtract(int n);
        double getValue();
        void setValue(int n);
}
class class1 implements one{
        double num=50.0;
        public void add(int n){
                num+=n;
        }
        public void subtract(int n){
                num-=n;
        }
        public void setValue(int n){
                num=1;
                for(int i=1;i<=n;i++){
                        num*=i;
                }
        }
        public double getValue(){
                return num;
        }
}
class class2 implements one{
        double num=20;
        public void add(int n){
                num+=(n+1)*n/2;
        }
        public void subtract(int n){
                num-=(n+1)*n/2;
        }
        public void setValue(int n){
                num=1;
                for(int i=1;i<=n;i++){
                        num*=i;
                }
        }
        public double getValue(){
                return num;
        }
}
public class interfaceDemo{
        public static void main(String args[]){
                double i;
                one aObj=new class1();
                i=aObj.getValue();
                System.out.println("The original value in class1 is:"+i);
                if(i<aObj.A){
                        aObj.add(30);
                        i=aObj.getValue();
                        System.out.println("After call add method is:"+i);
                }
                else{
                        aObj.subtract(30);
                        i=aObj.getValue();
                        System.out.println("After call subtract method is:"+i);
                }
                aObj=new class2();
                i=aObj.getValue();
                System.out.println("The original value in class2 is:"+i);
                if(i<aObj.A){
                        aObj.add(30);
                        i=aObj.getValue();
                        System.out.println("After call add method is:"+i);
                }
                else{
                        aObj.subtract(30);
                        i=aObj.getValue();
                        System.out.println("After call subtract method is: "+i);
                }

        }
}