我对java中的一个简单三角形计算程序有问题

主要方法：

import java.util.Scanner;

public class TriangeRunner
{
    // private instance variables
    private static double a, b, c;
    public static void main(String[] args)
    {
        // Instantiated an object from the class calcArea
        calcArea test = new calcArea();
        // Instantiated a Scanner object for user input.
        Scanner keyboard = new Scanner(System.in);
        System.out.print("Enter side A ::");
        a = keyboard.nextDouble();
        System.out.print("Enter side B ::");
        b = keyboard.nextDouble();
        System.out.print("Enter side C ::");
        c = keyboard.nextDouble();
        // Taking the referenced object test and calling 3 classes within 
        // within calcArea. (calcArea, setNums, toString)
        test.calcArea(a, b, c);
        test.setNums(a, b, c);
        test.toString();
    }
}

public class calcArea
{
    private double sa, sb, sc, s, area, perimeter;
    public void setNums(double a, double b, double c)
    {
        this.sa = a;
        this.sb = b;
        this.sc = c;
    }

    public void calcArea(double a, double b, double c)
    {
        perimeter = a + b + c;
        s = perimeter / 2;
        area = Math.sqrt((s * (s-sa) * (s-sb) * (s-sc)));
    }
    public String toString()
    {
        return ("The sides" + sa + ", " + sb + ", " + sc + " create the perimeter which is then divided by two which yields " + s + " which is then fed into herons formula: Math.sqrt(side * (side-sidea) * (side-sideb) * (side-sidec)) which produces an area of" + area);
    }
}

外部类：

import java.util.Scanner;

public class TriangeRunner
{
    // private instance variables
    private static double a, b, c;
    public static void main(String[] args)
    {
        // Instantiated an object from the class calcArea
        calcArea test = new calcArea();
        // Instantiated a Scanner object for user input.
        Scanner keyboard = new Scanner(System.in);
        System.out.print("Enter side A ::");
        a = keyboard.nextDouble();
        System.out.print("Enter side B ::");
        b = keyboard.nextDouble();
        System.out.print("Enter side C ::");
        c = keyboard.nextDouble();
        // Taking the referenced object test and calling 3 classes within 
        // within calcArea. (calcArea, setNums, toString)
        test.calcArea(a, b, c);
        test.setNums(a, b, c);
        test.toString();
    }
}

public class calcArea
{
    private double sa, sb, sc, s, area, perimeter;
    public void setNums(double a, double b, double c)
    {
        this.sa = a;
        this.sb = b;
        this.sc = c;
    }

    public void calcArea(double a, double b, double c)
    {
        perimeter = a + b + c;
        s = perimeter / 2;
        area = Math.sqrt((s * (s-sa) * (s-sb) * (s-sc)));
    }
    public String toString()
    {
        return ("The sides" + sa + ", " + sb + ", " + sc + " create the perimeter which is then divided by two which yields " + s + " which is then fed into herons formula: Math.sqrt(side * (side-sidea) * (side-sideb) * (side-sidec)) which produces an area of" + area);
    }
}

我对这个项目的关注是

创建一个计算三角形面积的简单程序，并

为了练习

没有错误，因此我认为我的错误在我的

toString

方法或

setNums

方法中

当我运行程序时，它会提示我输入边，然后就什么都没有了。我用BlueJ做这件事，因为我用Intellij做我的课堂作业，而且在其中添加类会很复杂

如果您需要进一步的澄清，请告诉我。

首先，请查看，因为您的类名以小写字母开头，这不是公认的做法。其他人读起来会感到困惑，特别是因为您有一个方法

public void calcArea（double a，double b，double c）

，它看起来像一个构造函数，但实际上不是

此外，您在这里似乎混合了不同的实施策略，因为您有：

    test.calcArea(a, b, c);
    test.setNums(a, b, c);

它在通过

setNums

设置变量之前计算面积，同时在

calcArea

类中，您不会利用这些变量：

private double sa，sb，sc

当您计算面积时，而是要求它们作为方法

calcArea

的参数

下面是我将对您的代码进行的一些改进的示例：

import java.util.Scanner;

public class Stuff
{
    // private instance variables
    private static double a, b, c;
    public static void main(String[] args)
    {
        // Instantiated an object from the class calcArea
        CalcArea test = new CalcArea();
        // Instantiated a Scanner object for user input.
        Scanner keyboard = new Scanner(System.in);
        System.out.print("Enter side A ::");
        a = keyboard.nextDouble();
        System.out.print("Enter side B ::");
        b = keyboard.nextDouble();
        System.out.print("Enter side C ::");
        c = keyboard.nextDouble();
        // Taking the referenced object test and calling 3 classes within 
        // within calcArea. (calcArea, setNums, toString)
        test.setNums(a, b, c);
        test.calcArea();
        System.out.println(test.toString());
        keyboard.close(); //don't forget to close resources.
    }
}


public class CalcArea
{
    private double sideA, sideB, sideC, s, area, perimeter;
    public void setNums(double sideA, double sideB, double sideC)
    {
        this.sideA = sideA;
        this.sideB = sideB;
        this.sideC = sideC;
    }

    public void calcArea()
    {
        perimeter = sideA + sideB + sideC;
        s = perimeter / 2;
        area = Math.sqrt((s * (s-sideA) * (s-sideB) * (s-sideC)));
    }
    public String toString()
    {
        return ("The sides" + sideA + ", " + sideB + ", " + sideC + " create the perimeter which is then divided by two which yields " + s + " which is then fed into herons formula: Math.sqrt(side * (side-sidea) * (side-sideb) * (side-sidec)) which produces an area of " + area);
    }
}

请注意，我是如何先设置类成员变量，然后计算面积，然后打印结果的：

        test.setNums(a, b, c);
        test.calcArea();
        System.out.println(test.toString());

还要注意类名

CalcArea

现在是如何以大写字母开头的，并且在读取方法

public void CalcArea（）

时，它就不那么容易混淆了

---

查看

public void calcArea（）

如何不接受任何参数，而是使用前面的

setNums

方法设置的值。

您似乎不了解构造函数是如何工作的。你应该写

calcrea test=newcalcrea（a，b，c）。您必须打印字符串。字符串和数字不会自动打印到屏幕上，否则您的程序将输出大量的废话，从而使屏幕计时。您没有打印它，而是希望它显示在您的控制台上。try:
System.out.println（test.toString（））
另外，看看OOP的一些例子。@Gendarme这是因为
Calcrea（double，double，double）
不是用来作为构造函数的，但由于类名不遵循Java标准命名，它看起来像一个构造函数。@D.B.你说得对。我读得太快了。我理解了类命名约定，我也看到了我在使用test.setNums（）和test.calcrea（）时的错误。我和它们混在一起，决定不使用它们。我认为我的toString方法返回可以很好地打印，但是现在我看到它打印toString方法更好。我不太确定“我认为我的toString方法返回可以很好地打印”是什么意思，因为在一个页面上调用
返回
和调用
println
方法之间有很大的区别。简单地返回一个值并不会导致它被打印出来。我理解，我的理解来自于知道System.out.print本质上会从一个方法返回值。