沒有實例化
package?math;
public?class?all?{
public?abstract?class?shape?{
public?abstract??void?area();
public?abstract??void?perimeter();?
}
public?abstract?class?circle?extends?shape?{
double?r?=?2.2;
????public?void?area(){
?System.out.println("circle?area?is?"+3.14*r*r);
????}
????public?void?perimeter(){
???? System.out.println("circle?perimete?is?"+2*r*3.14);
????}
}
public?abstract?class?rectangle?extends?shape?{
double?a=1.0;
double?b=1.0;
public?void?area(){
System.out.println("rectangle?ares?is"+a*b);
}
public?void?perimeter(){
System.out.println("recrangle?perimeter?is?"+2*(a+b));
}
}
public?static?void?main(String[]?args)?{
//?TODO?Auto-generated?method?stub
????shape?area1?=?new?circle();//這里顯示錯誤，Cannot?instantiate?the?type?circle
area1.perimeter();
????????area1.area();
????shape?area2?=?new?rectangle();//這里顯示錯誤，Cannot?instantiate?the?type?rectangle
area2.perimeter();
area2.area();
}
}問一下這個情況該怎么解決。找不到解決方法，謝謝
2016-12-18
子類不能加abstract修飾符
2016-12-01
public?abstract?class?shape?{
????????public?abstract??void?area();
????????public?abstract??void?perimeter();?
????}
?????
????public?abstract?class?circle?extends?shape?{
????????double?r?=?2.2;
????????public?void?area(){
?????????System.out.println("circle?area?is?"+3.14*r*r);
????????}
????????public?void?perimeter(){
????????????System.out.println("circle?perimete?is?"+2*r*3.14);
????????}
?????????
????}
?
????public?abstract?class?rectangle?extends?shape?{
????????double?a=1.0;
????????double?b=1.0;
????????public?void?area(){
????????????System.out.println("rectangle?ares?is"+a*b);
????????}
????????public?void?perimeter(){
????????????System.out.println("recrangle?perimeter?is?"+2*(a+b));
????????}
?
????}
?
public class test{
public?static?void?main(String[]?args)?{
????????//?TODO?Auto-generated?method?stub
????????shape?area1?=?new?circle();//這里顯示錯誤，Cannot?instantiate?the?type?circle
?
????????area1.perimeter();
????????????area1.area();
????????shape?area2?=?new?rectangle();//這里顯示錯誤，Cannot?instantiate?the?type?rectangle
????????area2.perimeter();
????????area2.area();
?
????}
}