Question

当我尝试编译此程序时，错误指向“new”一词。我正在尝试从carOrder类创建2个对象，我很烦恼！我以前在其他程序中遇到过这个问题，我不知道为什么，它会杀了我，请帮帮忙！

import java.text.DecimalFormat;
import java.util.Scanner;

public class CarOrder
private String buyer;
private String carType;
private double cost;
private int quantity;
private boolean taxStatus;
private double discountedCost;
private double taxAmount;

// Default Constructor
public void carOrder()
{
}

// Constructor
public void CarOrder(String buy, String car, double cos, int quan, boolean tax)
{
    buyer = buy;
    carType = car;
    cost = cos;
    quantity = quan;
    taxStatus = tax;
}

// Sets the company buying cars
public void setBuyer(String buy)
{
    buyer = buy;
}

// Sets the car type being purchased
public void setCarType(String car)
{
    carType = car;
}

// Sets cost of the cars being purchased
public void setCost(double cos)
{
    cost = cos;
}

// Sets the quantity of cars being purchased
public void setQuantity(int quan)
{
    quantity = quan;
}

// Sets tax status for the cars
public void setTaxStatus(boolean tax)
{
    taxStatus = tax;
}

// Returns name of buyer to user
public String getBuyer()
{
    return buyer;
}

// Returns type of car to user
public String getCarType()
{
    return carType;
}

// Returns cost to user
public double getCost()
{
    return cost;
}

// Returns quantity of cars to user
public int getQuantity()
{
    return quantity;
}

// Returns tax status to user
public boolean getTaxStatus()
{
    return taxStatus;
}

// Returns discounted cost to user
public double getDiscountedCost()
{
    if (quantity > 10)
        if (quantity > 20)
            discountedCost = cost - cost * .10;
        else
            discountedCost = cost - cost * .05;
    else
        discountedCost = cost;

    return discountedCost; 
}

// Returns tax amount to users
public double getTaxAmount()
{
    taxAmount = cost * .0625;
    return taxAmount;
}

public static void main(String[] args)
{
    Scanner keyboard = new Scanner(System.in);
    CarOrder speedy = new CarOrder("Speedy Rental", "Mini Cooper", 22150, 15, true);
    CarOrder zip = new CarOrder("Zip Car Co.", "Ford Fusion", 27495, 6, true);

    System.out.println("Enter first Buyer");
    String buyer1 = keyboard.nextLine();
}

}

Answer 1

public void CarOrder(String buy, String car, double cos, int quan, boolean tax)
{

应该是

public CarOrder(String buy, String car, double cos, int quan, boolean tax)
{

构造函数没有返回类型，甚至没有返回。

目前，您的类中有一个名为CarOrder的方法，因为它的返回类型为void，这会消除custructor的规则。如果你删除void，那么它就是一个构造函数，因为它与你的类名相同。

同样适用于没有argsaswell的构造函数。

public void CarOrder()

应该是

public  CarOrder()

Answer 2

你在公共类CarOrder之后错过了一个“{”......：）

Answer 3

当您不声明构造函数时，Java提供了一个没有参数的默认构造函数。当您声明CarOrder(String buy, String car, double cos, int quan, boolean tax)时，不再创建默认构造函数。你创建了一个名为carOrder的方法，这可能是试图使构造函数没有参数，但它有两个问题：

它有一个返回类型（void），构造函数没有一个
该名称与类不同（cardOrder与CarOrder不同，因为Java区分大小写）

如果您想进行new CarOrder()来电，只需添加以下代码：

public CarOrder() {
    //insert your implementation here
}

Answer 4

具有返回类型的构造函数被编译器视为方法。

为什么现在可以从我的班级创建对象

4 个答案: