當調用方法時，掃描儀輸入不起作用

Question

我對此比較陌生，任何幫助都會很棒。對於我的作業，我應該製作一個Triangle和一個TriangleTester類，它使用掃描儀控制值，以找出三角形的邊長，角度，周長等。我不是要求你做我的作業，但也許指向我在正確的方向。這只是一小部分，但它使我無法繼續。

我想不通的是如何讓變量我遇到方法輸入移動（如果是有道理的

這裏是我的三角代碼：

import java.math.*; 
import java.util.Scanner; 

public class Triangle 
{ 
private double A, B, C, D, h; 
public double x1, x2, x3, y1, y2, y3; 
public double lengthA, lengthB, lengthC; 
private double angleA, angleB, angleC; 
private double calcPerimeter, calcArea, getHeight; 

//Create new Triangle 
public Triangle(){ 
} 

//to get length of a (AB) use A = (x1, y1) & B = (x2,y2) 
public double getLengthC(){ 
double distance = Math.sqrt((Math.pow((x1-x2),2))+(Math.pow((y1-y2),2))); 
return distance; 
} 
} 

這裏是我的TriangleTester代碼：

import java.util.Scanner; 

public class TriangleTester 
{ 
public static void main(String[]args) 
{ 
Triangle triangle1 = new Triangle(); 

Scanner scan = new Scanner(System.in); 
System.out.println("Enter x1 for point A"); 
double x1 = scan.nextDouble(); 
System.out.println("Enter y1 for point A"); 
double y1 = scan.nextDouble(); 
System.out.println("Enter x2 for point A"); 
double x2 = scan.nextDouble(); 
System.out.println("Enter y2 for point A"); 
double y2 = scan.nextDouble(); 
System.out.println("Enter x3 for point A"); 
double x3 = scan.nextDouble(); 
System.out.println("Enter y3 for point A"); 
double y3 = scan.nextDouble(); 
System.out.println("Set up a Triangle with coordinates " +"("+x1+","+y1+")"+ ","+ "("+x2+","+y2+")" +","+ "("+x3+","+y3+")"); 

System.out.println("Length of side c " + triangle1.getLengthC()); 
} 
} 

出於測試目的，我想輸入的值：

0 
0 
4 
0 
3 
3 

並將c的長度計算爲4.我看到，當我在TriangleTester類中使用變量時，變量可以工作，但是當我從我的Triangle類調用某個方法時，這些值不起作用。

從我在哪裏，我覺得我有操縱三角形類，以便從掃描儀輸入我的移動到該區域....或者我可能是錯的

public Triangle(){} //I would have to add something here maybe? 

Answer 1

呀你」再右吧。由於您在TriangleTester中獲得用戶輸入，因此您需要將它們傳遞給Triangle類。

public Triangle(double x1, double x2, double x3, double y1, double y2, double y3) { 
    this.x1 = x1; 
    this.x2 = x2; 
    this.x3 = x3; 
    this.y1 = y1; 
    this.y2 = y2; 
    this.y3 = y3; 
} 

而且從用戶得到的值這樣之後創建Triangle對象：

Triangle triangle1 = new Triangle(x1, x2, x3, y1, y2, y3); 
System.out.println("Length of side c " + triangle1.getLengthC()); 

注：這是一個推薦的做法，使你的類的所有實例變量作爲private，並提供適當的獲取者和設置者他們。

Answer 2

問題不是在Scanner。你永遠不會填寫你的Triangle triangle1變量中的字段，所以所有的字段都有它們的默認值，即0.0。

只需從變量中填寫您的字段即可。例如：

triangle1.x1 = x1; 
//and on... 

但是，這是一個不好的做法，倒不如宣佈領域private，並使用setter方法作業，或具有接受必要的字段的構造函數。

class Triangle { 
    private double x1, x2, x3, y1, y2, y3; 
    public double getX1() { 
     return this.x1; 
    } 
    public void setX1(double x1) { 
     this.x1 = x1; 
    } 
    //other fields, getters and setters... 
} 

//... 
//in your TriangleTester#main method 
triangle1.setX1(x1); 
//same for other fields... 

Answer 3

試試這個

import java.util.Scanner; 

公共類MainClass {

public static void main(String[] args) { 


    Scanner scan = new Scanner(System.in); 
    System.out.println("Enter x1 for point A"); 
    double x1 = scan.nextDouble(); 
    System.out.println("Enter y1 for point A"); 
    double y1 = scan.nextDouble(); 
    System.out.println("Enter x2 for point A"); 
    double x2 = scan.nextDouble(); 
    System.out.println("Enter y2 for point A"); 
    double y2 = scan.nextDouble(); 
    System.out.println("Enter x3 for point A"); 
    double x3 = scan.nextDouble(); 
    System.out.println("Enter y3 for point A"); 
    double y3 = scan.nextDouble(); 
    System.out.println("Set up a Triangle with coordinates " +"("+x1+","+y1+")"+ ","+ "("+x2+","+y2+")" +","+ "("+x3+","+y3+")"); 

    Triangle triangle1 = new Triangle(x1,x2,y1,y2,x3,y3); 
    System.out.println("Length of side c " + triangle1.getLengthC()); 

} 

}

和

import java.math.*; 
import java.util.Scanner; 

public class Triangle 
{ 
private double A, B, C, D, h; 
public double x1, x2, x3, y1, y2, y3; 
public double lengthA, lengthB, lengthC; 
private double angleA, angleB, angleC; 
private double calcPerimeter, calcArea, getHeight; 

//Create new Triangle 
public Triangle(double x1,double x2,double y1,double y2,double x3, double y3){ 
    this.x1=x1; 
    this.y1=y1; 
    this.x2=x2; 
    this.y2=y2; 
    this.x3=x3; 
    this.y3=y3; 
} 

//to get length of a (AB) use A = (x1, y1) & B = (x2,y2) 
public double getLengthC(){ 
double distance = Math.sqrt((Math.pow((x1-x2),2))+(Math.pow((y1-y2),2))); 
System.out.println(distance); 
return distance; 
} 
} 

Answer 4

您還沒有設置您的triangle與你已經從Scanner

這種閱讀是可以做到的構造的一部分值的值：

public Triangle (double x1, double x2, double x3, double y1, double y2, double y3) { 
    this.x1 = x1; 
    this.x2 = x2; 
    this.x3 = x3; 
    this.y1 = y1; 
    this.y2 = y2; 
    this.y3 = y3; 
} 

或者您也可以設置setter方法Traingle類

void setX1 (double x1) 
{ 
    this.x1 = x1; 
} 

etc.