Question

我正在努力了解构造函数和方法的工作原理。我几乎有这些概念，只是我不知道如何设置它们。我特别不知道如何在ArrayLists中使用它们。

我正在尝试计算并打印矩形区域，评论的部分是我不知道如何设置的。

import java.util.ArrayList;
class RectangleStats
{
// Private instance variables
// length is an ArrayList which will contain integer values, width is an array which will contain integer
// values, and area is an array which will contain decimal values.

//code goes here for instance variables goes here


// The constructor for the RectangleStats class takes an ArrayList and an array as parameters for
// length and width, respectively.

// code for constructor goes here

// The calcRectangleArea() method calculates the area of rectangles using the length and
// the width assigned to the private instance variables and assigns the results to the area array of type
// double. This method does not return anything.

// code for the calcRectangleArea() method goes here

// The printArea() method prints the values assigned to the area array using the most appropriate
// type of loop. This method does not return anything.

// code for the printArea() method goes here
}

// The RectangleStatsTesterClass assigns the length of two rectangles to an ArrayList and assigns the
// width of two rectangles to an array. The calcRectangleArea() and printArea() methods are invoked to
// calculate and print the area of the two rectangles.
public class RectangleStatsTesterClass2
{
public static void main(String[] args)
{
ArrayList intLength = new ArrayList();
intLength.add(7);
intLength.add(5);
int [ ] intWidth = {3, 4};

RectangleStats rectStats = new RectangleStats(intLength, intWidth);
rectStats.calcRectanglePerimeter();
rectStats.printArea();
}
}

Answer 1

试试这样：

import java.util.ArrayList;
import java.util.List;
class RectangleStats
{

    private List<Integer> length;

    private int[ ] width;

    double areas[];

    RectangleStats(List<Integer> length, int[] width){
        this.length = length;
        this.width = width;
        this.areas = new double[this.width.length];
    }

    private void calcRectangleArea(){
        for(int i=0; i<width.length; i++){
            areas[i] = length.get(i) * width[i];
        }
    }

    public void printArea(){
        calcRectangleArea();
        for(int i=0; i<areas.length; i++){
            System.out.println("Area " + i + " : " + areas[i]);
        }
    }

    public void calcRectanglePerimeter(){
        for(int i=0; i<width.length; i++){
            System.out.println("Parameter for "+ i +"th Rectangle : " + (2 * (length.get(i) + width[i])));
        }
    }
}

public class RectangleStatsTesterClass2
{
    public static void main(String[] args)
    {
        ArrayList<Integer> intLength = new ArrayList<Integer>();
        intLength.add(7);
        intLength.add(5);
        int [ ] intWidth = {3, 4};

        RectangleStats rectStats = new RectangleStats(intLength, intWidth);
        rectStats.calcRectanglePerimeter();
        rectStats.printArea();
    }
}

如何使用ArrayList设置构造函数和方法？

1 个答案: