Question

我目前正在尝试完成这个Java编程实践项目而且陷入困境......我不确定我的问题是什么，所以我能得到一些帮助吗？

以下是完整的代码：

package AreaElseIf;

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

public class AreaElseIf {

    public static void main(String[] args) {

        final double PI = 3.14;
        Scanner input = new Scanner(System.in);

        System.out.println("This program uses an else/if statement.");

        System.out.println("1 = circle, 2 = square, 3 = rectangle, 4 = triangle.");
        int object = input.nextInt();

        if (input = 1) {
            System.out.println("Enter circle's radius: ");
            double radius = input.nextDouble();
            double cArea = radius * radius * PI;
            System.out.println("The area of a circle with the radius of " + radius + " is " + cArea + ".");
        } 
        else if (input = 2) {
            System.out.println("Enter length of square's sides: ");
            double sSide = input.nextDouble();
            double sArea = sSide * sSide;
            System.out.println("The area of a square with a side length of " + sSide + " is " + sArea + ".");
        } 
        else if (input = 3) {
            System.out.println("Enter length of rectangle's base: ");
            double base = input.nextDouble();
            System.out.println("Enter length of rectangle's height: ");
            double height = input.nextDouble();
            double rArea = base * height;
            System.out.println("The area of a rectangle with a base length of " + base + " and a height of " + height + " is " + rArea + ".");
        }
        else if (input = 4) {
            System.out.println("Enter traingle's side length: ");
            double tSide = input.nextDouble();
            double tArea = tSide * tSide * tSide;
            System.out.println("The area of a triangle with a side length of " + tSide + " is " +  tArea + ".");
        }
        else {
        System.out.println("Error: Please enter a number between 1-4 only.");       
        }

    }//end main
}//end class

程序的目的是要求用户输入1到4之间的数字，并将每个数字分配给一个形状。如果单击该形状的数字，它会向您询问几个问题，以便计算所述形状的面积。这个程序的重点是使用else / if来完成它。

我得到的错误只是“（输入= 1,2,3,4 ......）”的行 input =＃都是带下划线的红色。

错误的措辞如下： “类型不匹配。无法从int转换为扫描仪” “类型不匹配。无法从扫描仪转换为布尔值”

我不明白这些意思是什么，并希望得到一些帮助。

Answer 1

问题的第一部分是您在每个if / else语句中使用了赋值运算符=。要测试相等性，请使用==运算符，因为它返回bool（如果相等则为true，否则为false）。

问题的后半部分是你根据你的int值测试你的扫描仪，你应该在那里测试扫描仪的结果（在你的情况下看起来像object检索用户的int）。 / p>

最终你的if应该是这样的：

if(object == 1) { ...

Answer 2

而不是做

if (input = 1)

你需要做

if (object == 1)

在您的代码中，input是Scanner对象，您正在尝试为其分配（=）整数。相反，您希望比较从扫描仪获得的整数输入（object），并将其（==）与整数值进行比较。

Answer 3

问题在这里if (input = 1)

首先你尝试将输入设置为1，而不是比较值，其次输入是扫描仪而不是整数

要修复它，请更改为if (object == 1)，它将起作用object是您从扫描仪读取的整数，==是比较。

另外，您可以使用switch / case语句对您的简单问题进行排序，但这是不同的故事

Answer 4

    if (input == 1) {
        System.out.println("Enter circle's radius: ");
        double radius = input.nextDouble();
        double cArea = radius * radius * PI;
        System.out.println("The area of a circle with the radius of " + radius + " is " + cArea + ".");
    } 
    else if (input == 2) {
        System.out.println("Enter length of square's sides: ");
        double sSide = input.nextDouble();
        double sArea = sSide * sSide;
        System.out.println("The area of a square with a side length of " + sSide + " is " + sArea + ".");
    } 
    else if (input == 3) {
        System.out.println("Enter length of rectangle's base: ");
        double base = input.nextDouble();
        System.out.println("Enter length of rectangle's height: ");
        double height = input.nextDouble();
        double rArea = base * height;
        System.out.println("The area of a rectangle with a base length of " + base + " and a height of " + height + " is " + rArea + ".");
    }
    else if (input == 4) {
        System.out.println("Enter traingle's side length: ");
        double tSide = input.nextDouble();
        double tArea = tSide * tSide * tSide;
        System.out.println("The area of a triangle with a side length of " + tSide + " is " +  tArea + ".");
    }
    else {
    System.out.println("Error: Please enter a number between 1-4 only.");       
    }

Answer 5

Java中的等式比较器是==，而不是=。您要检查的int变量名为object，而不是input

替换

if (input =

带

if (object ==

Answer 6

基本上你有

Scanner input = new Scanner(System.in);
int object = input.nextInt();
if (input = 1) {

1 /你无法测试int的输入。 object 是一个int

2 /用＆＃39; ==＆＃39;进行测试。不是＆＃39; =＆＃39;这是一种矫揉造作

if (object == 1) {

应解决您的问题

Answer 7

对于整数使用＆＃34; ==＆＃34; if（输入== 1）{..这里..} ＆＃34; =＆＃34;是一个分配运营商， ==对所有变量的行为相同：它测试这些变量的值是否相等。在Object obj的情况下，obj是对对象的引用。由于==测试两个对象引用是否具有相同的值，因此测试它们是否引用相同的对象（即引用是否相等）。对于您的应用程序，我建议您使用switch语句http://docs.oracle.com/javase/tutorial/java/nutsandbolts/switch.html

干杯，伊德里斯。

Answer 8

已经有很多答案可以指导您进行更改

if(input = 1)

到

if (object == 1)

我想建议另一个解决方案： switch（）语句。为什么？ Switch（）针对两个以上的分支进行了优化，通常更容易阅读（在我看来）。使用switch（）的代码如下所示：

package AreaElseIf;

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

public class AreaElseIf {

public static void main(String[] args) {

    final double PI = 3.14;
    Scanner input = new Scanner(System.in);

    System.out.println("This program uses an else/if statement.");

    System.out.println("1 = circle, 2 = square, 3 = rectangle, 4 = triangle.");
    switch( input.nextInt())
    {
        case 1:
            System.out.println("Enter circle's radius: ");
            double radius = input.nextDouble();
            double cArea = radius * radius * PI;
            System.out.println("The area of a circle with the radius of " + radius + " is " + cArea + ".");
            break;

        case 2:
            System.out.println("Enter length of square's sides: ");
            double sSide = input.nextDouble();
            double sArea = sSide * sSide;
            System.out.println("The area of a square with a side length of " + sSide + " is " + sArea + ".");
            break;        

        case 3:
            System.out.println("Enter length of rectangle's base: ");
            double base = input.nextDouble();
            System.out.println("Enter length of rectangle's height: ");
            double height = input.nextDouble();
            double rArea = base * height;
            System.out.println("The area of a rectangle with a base length of " + base + " and a height of " + height + " is " + rArea + ".");
            break;

        case 4: 
            System.out.println("Enter traingle's side length: ");
            double tSide = input.nextDouble();
            double tArea = tSide * tSide * tSide;
            System.out.println("The area of a triangle with a side length of " + tSide + " is " +  tArea + ".");
            break;

        default:
             System.out.println("Error: Please enter a number between 1-4 only.");       
    }
}//end main

请注意，在此代码中，您不需要（int object）变量。

Answer 9

尝试在if语句中将input更改为object。和=到==

需要帮助 - Java Else / If Statement

9 个答案: