java - 设置值并调用 get 方法后程序返回 0？

Question

我正在开发一个java项目，据我所知，我已经完成了所有工作，但是当我运行该程序时，应用程序上的第一组编码执行了它应该执行的操作，但是更新后的金额给我 0 的价格和金额。第二个对象的编码也是如此，原始发票信息工作正常，除了以下事实:对于更新后的代码，当它们应该为零时，它会给出负值，除此之外，它工作正常。对于更新的发票金额，它给我的价格和最终金额为 0。我看不到任何错误，它全部编译并运行。这是类代码。

public class Invoice
{
private String partNumber;
private String partDescription;
private int quantity;
private double price;

public Invoice (String part,String description, int quan, double value)
{
    partNumber = part;
    partDescription = description;

    if(quan > 0);
        quantity = quan;

    if(price > 0.0);
        price = value;

}
public void setpartNumber(String part)
{
    partNumber = part;
}
public String getpartNumber()
{
    return partNumber;
}
public void setpartDescription(String description)
{
    partDescription = description;      
}
public String getpartDescription()
{
    return partDescription;
}
public void setquantity(int quan)
{
    if(quan > 0);
        quantity = quan;
    if(quan <= 0);
        quan = 0;
}

public int getquantity()
{

    return quantity;
}
public void setprice(double value)
{
    if(value > 0.0);
        price = value;

    if(value <= 0.0);
        price = 0.0;

}
public double getprice()
{
    return price;
}
public double getInvoiceAmount()
{
    return (getquantity() * getprice());

}

}

这是应用程序代码。

public class InvoiceTest
{
public static void main (String args[])
{   
    Invoice invoiceA = new Invoice("1234", "Hammer",2,14.95 );


    System.out.println("Original Invoice Information");         
    System.out.printf("Part Number: %s\n", invoiceA.getpartNumber());
    System.out.printf("Description: %s\n",invoiceA.getpartDescription());
    System.out.printf("Quantity: %d\n", invoiceA.getquantity());
    System.out.printf("Price: %.2f\n", invoiceA.getprice());
    System.out.printf("Invoice Amount: %.2f\n",invoiceA.getInvoiceAmount());


    invoiceA.setpartNumber("001234");
    invoiceA.setpartDescription("Yellow Hammer");
    invoiceA.setquantity(3);
    invoiceA.setprice(19.49);
    System.out.println();

    System.out.println("Updated Invoice Information");
    System.out.printf("Part Number: %s\n", invoiceA.getpartNumber());
    System.out.printf("Description: %s\n",invoiceA.getpartDescription());
    System.out.printf("Quantity: %d\n",invoiceA.getquantity());
    System.out.printf("Price: %.2f\n",invoiceA.getprice());
    System.out.printf("Invoice Amount: %.2f\n",invoiceA.getInvoiceAmount());

    Invoice invoiceB = new Invoice("5678","Paint Brush",-5,-9.99);


    System.out.println("\nOriginal Invoice Information");           
    System.out.printf("Part Number: %s\n", invoiceB.getpartNumber());
    System.out.printf("Description: %s\n",invoiceB.getpartDescription());
    System.out.printf("Quantity: %d\n", invoiceB.getquantity());
    System.out.printf("Price: %.2f\n", invoiceB.getprice());
    System.out.printf("Invoice Amount: %.2f\n",invoiceB.getInvoiceAmount());


    invoiceB.setquantity(3);
    invoiceB.setprice(9.49);
    System.out.println();

    System.out.println("Updated Invoice Information");
    System.out.printf("Part Number: %s\n", invoiceB.getpartNumber());
    System.out.printf("Description: %s\n",invoiceB.getpartDescription());
    System.out.printf("Quantity: %d\n",invoiceB.getquantity());
    System.out.printf("Price: %.2f\n",invoiceB.getprice());
    System.out.printf("Invoice Amount: %.2f\n",invoiceB.getInvoiceAmount());


}
}

Answer 1

整个代码中的 if 条件后面有额外的分号。真正导致您的错误的那个:

public void setprice(double value)
{
    if(value > 0.0);
        price = value;

    if(value <= 0.0);
        price = 0.0;

}

分号充当 if 的主体，因此后续语句始终会执行，并且 price 始终设置为 0。删除分号:

public void setprice(double value)
{
    if(value > 0.0)
        price = value;

    if(value <= 0.0)
        price = 0.0;

}

以类似方式更改代码中的其他 if。