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我遇到让TestPolygon.java正常运行的问题。 “//构造函数创建四个多边形，其任何值不等于defualt值或相互之间的Polygon [] P_array = {new Polygon（10,5.0,1.0,3.0），new Polygon（6,3,2） ，5），新的Polygon（4,11,4,3），新的Polygon（5,12,6,7）};“我的代码行不断回来，每个新语句都说错误”没有合适的构造函数找到多边形（int，double，double，double）。附图。

/* File: Polygon.java
* Author: Darren Pirtle Jr.
* Date: November 16, 2016
* Purpose: Design a Java class
* named Polygon
*/

import java.lang.Math;

public class Polygon {
 private int numSides;
 private double sideLength;
 private double xCoord;
 private double yCoord;
 private double apothem;
 private double perimeter;

 //Constructor that creates a Polygon using the defaults
 public Polygon(){
     numSides = 4;
     sideLength = 10.0;
     xCoord = 0.0;
     yCoord = 0.0;
     apothem = 5.0;
}
 //Constructor that uses the specified numbers
 public Polygon(int s,double sL,double x,double y,double a, double p){
     setNumSides(s);
     setSideLength(sL);
     setXCoord(x);
     setYCoord(y);
     setApothem(a);
}

 // A getArea() method that returns a double value for the area of the polygon
 public double getArea() {
 return .5*apothem*perimeter;
}

 // Getter and setter for all data fields
 public int setNumSides(int s){
      numSides = s;
      return numSides;
}
 public double setSideLength(double sL){
      sideLength = sL;
      return sideLength;
}
 public double setXCoord(double x){
      xCoord = x;
      return xCoord;
}
 public double setYCoord(double y){
      yCoord = y;
      return yCoord;
}
 public double setApothem(double a){
      apothem = a;
      return apothem;
}
 public double setPerimeter(double p){
       perimeter = p;
       return perimeter;
}
 public int getNumSides() {
 return numSides; 
 }
 public double getSideLength() { 
 return sideLength; 
 }
 public double getXCoord() { 
 return xCoord; 
 }
 public double getYCoord() {
 return yCoord; 
 }
 public double getApothem() {
 return apothem;
 }
 public double getPerimeter() {
 return perimeter;
 }

 //A toString() that displays the values in string format
 public String toString(){
      return "("+numSides+", "+String.format("%.1f",sideLength)+", "+String.format("%.1f",xCoord)+", "+String.format("%.1f",yCoord)+")";
 }
}

/* File: Polygon.java
* Author: Darren Pirtle Jr.
* Date: November 16, 2016
* Purpose: Design a Java class
* named Polygon
*/

//Import necessary packages
import java.util.Scanner;
import java.text.DecimalFormat;
import java.lang.Math;

class TestPolygon{
    public static void main(String[] args){

    //Constructor that creates one polygon with no argument
    Polygon P = new Polygon();

    //Constructor that creates four polygons with any value that are not equal to the defualt value or to each other
    Polygon[] P_array = {new Polygon(10,5.0,1.0,3.0), new Polygon(6,3,2,5), new Polygon(4,11,4,3), new Polygon(5,12,6,7)};

    //Constructor that calls all methods and displays results
    System.out.println("toString() results: "+P);
    System.out.println("getNumSides() results: "+ P.getNumSides());
    System.out.println("getSideLength() results: "+ P.getSideLength());
    System.out.println("getXCoord() results: "+ P.getXCoord());
    System.out.println("getYCoord() results: "+ P.getYCoord());
    System.out.println("getPerimeter() results: "+ P.getPerimeter());
    System.out.println("setNumSides(4) results: "+ P.setNumSides(4));
    System.out.println("setSideLength(3.0) results: "+ P.setSideLength(3.0));
    System.out.println("setXCoord(2.0) results: "+ P.setXCoord(2));
    System.out.println("setYCoord(2.0) results: "+ P.setYCoord(2));
    for(int i=0; i<P_array.length; i++)
    {
    System.out.println("toString() results: "+P_array[i]);
    System.out.println("getNumSides() results: "+ P_array[i].getNumSides());
    System.out.println("getSideLength() results: "+ P_array[i].getSideLength());
    System.out.println("getXCoord() results: "+ P_array[i].getXCoord());
    System.out.println("getYCoord() results: "+ P_array[i].getYCoord());
    System.out.println("getPerimeter() results: "+ P_array[i].getPerimeter());
    System.out.println("setNumSides(4) results: "+ P_array[i].setNumSides(4));
    System.out.println("setSideLength(3.0) results: "+ P_array[i].setSideLength(3.0));
    System.out.println("setXCoord(2.0) results: "+ P_array[i].setXCoord(2));
    System.out.println("setYCoord(2.0) results: "+ P_array[i].setYCoord(2));
    }
    }
}

enter image description here

Answer 1

问题是你用4个参数调用Polygon（），但你没有4参数构造函数。你有一个没有arg

 public Polygon(){
     numSides = 4;
     sideLength = 10.0;
     xCoord = 0.0;
     yCoord = 0.0;
     apothem = 5.0;
}

和6 arg

public Polygon(int s,double sL,double x,double y,double a, double p){
 setNumSides(s);
 setSideLength(sL);
 setXCoord(x);
 setYCoord(y);
 setApothem(a);
}

但你正在打电话

new Polygon(10,5.0,1.0,3.0)

您可以为新的Polygon调用添加2个参数，也可以从6个arg构造函数中删除2个参数，或者创建一个带4个参数的构造函数。

Answer 2

您的参数化构造函数有6个参数，即

• int s
• double sL
• double x
• double y
• double a
• double p

但是，当你构造多边形时，你只传入四个值，即 new Polygon(10,5.0,1.0,3.0)

由于你没有在构造函数中使用最后一个参数，即＆＃34; double p＆＃34;，你的构造函数应该是：public Polygon(int s,double sL,double x,double y,double a)

Answer 3

错误消息说明了一切：

  

没有为Polygon找到合适的构造函数（int，double，double，double）。

它只是意味着Java无法使用参数(int, double, double, double)找到类Polygon的构造函数（这是您在创建Polygon对象时使用的）

如果你看一下类Polygon的构造函数：

您创建了2个构造函数：

• 没有参数构造函数

• 包含6个参数的构造函数（int，double，double，double，double，double）

因此，在创建Polygon对象时，请确保执行以下操作：

new Polygon(); 
or
new Polygon(int, double, double, double, double, double);

示例：

Polygon p1 = new Polygon();
Polygon p2 = new Polygon(10, 2.5, 3.5, 4.5, 5.5, 6.5);
Polygon p3 = new Polygon(10, 20, 30, 40, 50, 60);    //this is ok too

目前，您只提供4个参数：

new Polygon(10, 5.0, 1.0, 3.0), 
             ^   ^    ^    ^
             |   |    |    |
            int  d    d    d  (d for double)