Question

我一直在收到错误：

3 errors found:
File: C:\Users\TUFRob\Documents\Computer Science II\Retail\RetailItemDemo.java  [line: 6]
Error: constructor RetailItem in class RetailItem cannot be applied to given types;
  required: int,double,java.lang.String
  found: no arguments
  reason: actual and formal argument lists differ in length
File: C:\Users\TUFRob\Documents\Computer Science II\Retail\RetailItemDemo.java  [line: 7]
Error: constructor RetailItem in class RetailItem cannot be applied to given types;
  required: int,double,java.lang.String
  found: java.lang.String,int,double
  reason: actual argument java.lang.String cannot be converted to int by method invocation conversion
File: C:\Users\TUFRob\Documents\Computer Science II\Retail\RetailItemDemo.java  [line: 8]
Error: constructor RetailItem in class RetailItem cannot be applied to given types;
  required: int,double,java.lang.String
  found: no arguments
  reason: actual and formal argument lists differ in length

当我尝试运行我的java程序时：

public class RetailItemDemo
{
    public static void main(String[]args)
    {
        RetailItem item1 = new RetailItem();
        RetailItem item2 = new RetailItem("Designer Jeans", 40, 34.95);
        RetailItem item3 = new RetailItem();
    }
}

这个班级：

public class RetailItem
{
    private String description;
    private int unitsOnHand;
    private double price;

    public RetailItem(int unitsOnHand, double price, String description)
    {
        this.unitsOnHand = unitsOnHand;
        this.price = price;
        this.description = description;
    }
}

我无法查看可能导致错误的原因

Answer 1

RetailItem的构造函数有输入参数，如int，double和string。您应该根据它的定义按顺序传递参数值。否则它会给compile time error。在这里你犯了同样的错误。

问题1：

RetailItem item2 = new RetailItem(40, 34.95, "Designer Jeans");

而不是

RetailItem item2 = new RetailItem("Designer Jeans", 40, 34.95);

问题2：

RetailItem item3 = new RetailItem();

此语法将尝试调用默认构造函数。在RetailItem类中，您没有定义默认构造函数，因为它也会给出compile time error。默认构造函数仅在没有定义其他构造函数时才存在，否则您必须手动定义它。

参考：what is constructor in java?

Answer 2

您的RetailItem只有一个构造函数：

public RetailItem(int unitsOnHand, double price, String description){...}

然后，你的所有电话都错了：

//Problem 1:  wrong because you have no constructor with no param
RetailItem item1 = new RetailItem();
RetailItem item3 = new RetailItem();

和

// Problem 2:
RetailItem item2 = new RetailItem("Designer Jeans", 40, 34.95);
//wrong because your Constructor is RetailItem(int, double, String)
// not RetailItem(String, int, double)

如何解决：

在您的课程中添加默认的Constrcutor（无参数）以解决问题1

public RetailItem(){
}

要解决问题2，请将第11行更改为：

RetailItem item2 = new RetailItem( 40, 34.95,"Designer Jeans");

＆＃34;构造函数不能应用于给定类型＆＃34;错误

2 个答案: