创建不同对象的实例列表并使用这些对象 [英] Creating instance list of different objects and using these objects

问题描述

Java 代码:

import java.util.ArrayList;
import java.util.List;

class apple{
int price;

public void myFunction(int iPrice)
{
    price=iPrice;
}
}

class orange{
int price;

public void myFunction(int iPrice)
{
    price=iPrice;
}
}

public class main {

public static void main(String[] args) {
    List <Object> list= new ArrayList<>();

    //create 3 apple object to list
    list.add( new apple() );
    list.add( new apple() );
    list.add( new orange() );

    list.get(0). /* "get(0)." this isn't using apple object and my function */

}
}

推荐答案

list.get(0) 方法返回一个 Object 引用，因此你必须向下转型它到 apple.有点像这样:

The method list.get(0) returns an Object reference, therefore you have to downcast cast it to apple. Somewhat like this:

apple a = (apple)list.get(0); 

然后调用函数.

注意:Java 中的类名最好使用大写字母，例如 Apple、Orange

Note: It is a good practice that class names in Java be in capital letters like Apple, Orange

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