Question

我正在研究java中的平均值，中位数。我创建了一个程序，但我无法在其上正确实现继承。在我的代码中，对于每个继承的类对象，它的请求输入。

我希望输入只需要一次，然后使用继承均值和模式进行计算。请建议。

import java.io.*;
import java.util.*;



class A
{

    int a[];
    int no;


    A()
    {

        System.out.println("Number of elements for an array : ");
        Scanner in1 = new Scanner(System.in);
        no = in1.nextInt();

        a = new int[no];

        for(int i=0; i<no; i++)
        {
            System.out.println("Enter elements : ");
            Scanner in2 = new Scanner(System.in);
            a[i] = in2.nextInt();           

        }
    }

    void sort()
    {
        int tmp;
        for(int i=0; i<no-1; i++)
        {
            for(int j=i+1; j<no; j++)
            {
                System.out.println("a[i] : " + a[i] + " a[i+1] : " + a[i+1]);
                if (a[i]>a[j])
                {
                    tmp = a[i];
                    a[i] = a[j];
                    a[j] = tmp;     
                }
            }   
        }
    }


    void display()
    {
        System.out.println();
        for(int i=0; i<no; i++)
        {
            System.out.println(a[i]);
        }
    }


}


class B extends A
{

    int tot = 0; 
    float mean;


    void get_mean()
    {
        System.out.println("no : " + no);
        for(int i=0; i<no; i++)
        {
            tot += a[i];
        }
        System.out.println("tot : " + tot);
        mean = (float) tot/no;
        System.out.println("mean : " + mean);
    }

} 


class C extends A
{

    void median()
    {
        float median;
        if(no%2==0)
        {
            int middle = no/2;
            median = (float)((a[middle] + a[middle/2])/2);
        }
        else
        {
            median = a[(no/2)];
        }
        System.out.println("median : " + median);   
    }

} 


class test
{
       public static void main (String arg[]) throws IOException
       {



        B obj1 = new B();
        obj1.get_mean();

        C obj2 = new C();
        obj2.sort();
        obj2.median();


       }
}

Answer 1

继承为您提供通用API和公共基本类型而不是数据。

添加复制构造函数，该构造函数接受“A”参数，然后从传递的“A”对象复制属性。像这样：

package com.example;

import java.io.IOException;
import java.util.Scanner;

class A {

    int a[];
    int no;

    A() {
    }

    void init() {

        System.out.println("Number of elements for an array : ");
        Scanner in1 = new Scanner(System.in);
        no = in1.nextInt();

        a = new int[no];

        for (int i = 0; i < no; i++) {
            System.out.println("Enter elements : ");
            Scanner in2 = new Scanner(System.in);
            a[i] = in2.nextInt();

        }
    }

    void sort() {
        int tmp;
        for (int i = 0; i < no - 1; i++) {
            for (int j = i + 1; j < no; j++) {
                System.out.println("a[i] : " + a[i] + " a[i+1] : " + a[i + 1]);
                if (a[i] > a[j]) {
                    tmp = a[i];
                    a[i] = a[j];
                    a[j] = tmp;
                }
            }
        }
    }

    void display() {
        System.out.println();
        for (int i = 0; i < no; i++) {
            System.out.println(a[i]);
        }
    }

}

class B extends A {

    B(A obj) {
        no = obj.no;
        a = new int[obj.a.length];
        System.arraycopy( obj.a, 0, a, 0, obj.a.length );
    }

    int tot = 0;
    float mean;

    void get_mean() {
        System.out.println("no : " + no);
        for (int i = 0; i < no; i++) {
            tot += a[i];
        }
        System.out.println("tot : " + tot);
        mean = (float) tot / no;
        System.out.println("mean : " + mean);
    }

}

class C extends A {

    C(A obj) {
        no = obj.no;
        a = new int[obj.a.length];
        System.arraycopy( obj.a, 0, a, 0, obj.a.length );
    }

    void median() {
        float median;
        if (no % 2 == 0) {
            int middle = no / 2;
            median = ((a[middle] + a[middle / 2]) / 2);
        } else {
            median = a[(no / 2)];
        }
        System.out.println("median : " + median);
    }

}

public class Test {

    public static void main(String arg[]) throws IOException {

        A objA = new A();
        objA.init();

        B obj1 = new B(objA);
        obj1.get_mean();

        C obj2 = new C(objA);
        obj2.sort();
        obj2.median();

    }
}

但更好的方法是使用组合而不是继承。让你的A类收集数据然后将这个“数据”对象注入B，C。 B和C不需要是“IS-A”对象。它们应该是“HAS-A”对象。

平均值和中位数的继承示例

1 个答案: