Shape：
package?com.test;
public?interface?Shape?{
public?double?area();
public?double?perimeter();
}
Circle：?
package?com.test;
public?class?Circle?implements?Shape?{
double?r?=?5;
double?pi?=?3.14;
@Override
public?double?area()?{
return?pi*r*r;
}
@Override
public?double?perimeter()?{
return?2*pi*r;
}
}
Rectangle：
package?com.test;
public?class?Rectangle?implements?Shape?{
double?a?=?3;
double?b?=?4;
@Override
public?double?area()?{
return?a*b;
}
@Override
public?double?perimeter()?{
return?2*(a+b);
}
}
Triangle：?
package?com.test;
public?class?Triangle?implements?Shape?{
double?a?=?4;
@Override
public?double?area()?{
return?a*a;
}
@Override
public?double?perimeter()?{
return?4*a;
}
}
3.
shape：
package?com.test.abstr;
public?abstract?class?Shape?{
public?double?area(){
return?0.0;
}
public?double?perimeter(){
return?0.0;
}
}
Circle：?
package?com.test.abstr;
public?class?Circle?extends?Shape?{
double?r?=?5;
double?pi?=?3.14;
public?double?area(){
return?pi*r*r;
}
public?double?perimeter(){
return?2*pi*r;
}
}
Rectangle：?
package?com.test.abstr;
public?class?Rectangle?extends?Shape?{
double?a?=?3;
double?b?=?4;
public?double?area()?{
return?a*b;
}
public?double?perimeter()?{
return?2*(a+b);
}
}
Triangle：
package?com.test.abstr;
public?class?Triangle?extends?Shape?{
double?a?=?4;
public?double?area()?{
return?a*a;
}
public?double?perimeter()?{
return?4*a;
}
}
Test：
package?com.test.abstr;
public?class?Test?{
/**
?*?@param?args
?*/
public?static?void?main(String[]?args)?{
Shape?s1?=?new?Circle();
System.out.println(s1.area());
System.out.println(s1.perimeter());
Shape?s2?=?new?Rectangle();
System.out.println(s2.area());
System.out.println(s2.perimeter());
Shape?s3?=?new?Triangle();
System.out.println(s3.area());
System.out.println(s3.perimeter());
}
}
結果：
78.5
31.400000000000002
12.0
14.0
16.0
16.0
4.package?com.test.four;
public?class?Person?{
String?name;
public?void?pay(double?num){
System.out.println(name+"***花費"+num+"元");
}
}
package?com.test.four;
public?class?ShoppingCart?{
public?String?name;
public?double?price;
public?int?count;
}
package?com.test.four;
public?class?Checkstand?{
public?static?void?main(String[]?args)?{
double?count?=?0.0;
ShoppingCart?sc1?=?new?ShoppingCart();
sc1.name?=?"牙膏";
sc1.price?=?6.5;
sc1.count?=?1;
count?=?count?+?getCount(sc1);
ShoppingCart?sc2?=?new?ShoppingCart();
sc2.name?=?"香皂";
sc2.price?=?4.5;
sc2.count?=?1;
count?=?count?+?getCount(sc2);
ShoppingCart?sc3?=?new?ShoppingCart();
sc3.name?=?"洗衣粉";
sc3.price?=?16.5;
sc3.count?=?1;
count?=?count?+?getCount(sc3);
Person?person?=?new?Person();
person.name?=?"小花";
person.pay(count);
}
public?static?double?getCount(ShoppingCart?sc){
System.out.println(sc.name+"----"+sc.count+"件"+sc.price?*?sc.count+"元");
return?sc.price?*?sc.count;
}
}
結果：
牙膏 ----1件 ? 6.5元
香皂 ----1件 ? 4.5元
洗衣粉 ----1件 ? 16.5元
小花***花費27.5元
個人建議，如果是初學者還是自己多去思考，多去練習，如果以後想從事軟件開發方面的，更需要多練多看多想。