Java 意外的无限循环

Question

我的问题是我的方法进入了意外的无限循环，但我无法确定原因。该方法应该从用户那里获取输入并将其分配给三个不同的对象。然而，在循环运行两次并要求用户输入第三个对象的名称后，程序无限循环。我应该指出，我对 java 和学习编程还比较陌生。

这是代码（我已经用 !!!! 开始了 cmets，我认为这与问题有关）：

private void readInput()    
//This method accepts input from the user about product data and sets the values of 
//product1, product2 and product3
//Also validates all input so as not to crash the program if the user enters incorrect data
{       
    String name;        
    int demandRate, productChoice=1; 
    final int MAXPRODUCTS=3;
    double setupCost, unitCost, inventoryCost, sellingPrice;

    Scanner console = new Scanner(System.in);

    while (productChoice <= MAXPRODUCTS)    
    //A loop that makes the user enter data for all three products and then stops after the third entry
    {                                      
        System.out.println("Please enter the product's name: ");
        name = console.next();       
        matesStore.isAProduct(name);     // checks whether the product name the user has entered is unique.
        while (matesStore.isAProduct(name))  
        //If a name that has already been entered is found, the user will be asked to reenter the name
        {
            System.out.println("That name is already in use. Please choose another: "); 
            name = console.next();
        }
        while (!matesStore.isAProduct(name))
        //If a name has not been used, the name is added to the product
        {
            matesStore.addProduct(name); //!!!!I suspect the problem is this line.
        }            
        System.out.println("Please enter the product's demand rate: ");
        demandRate = console.nextInt();                         
        System.out.println("Please enter the product's setup cost: ");
        setupCost = console.nextDouble();
        System.out.println("Please enter the product's unit cost: ");
        unitCost = console.nextDouble();
        System.out.println("Please enter the product's inventory cost: ");
        inventoryCost = console.nextDouble();
        System.out.println("Please enter the product's selling price: ");
        sellingPrice = console.nextDouble();
        matesStore.addData(productChoice, demandRate, setupCost, unitCost, inventoryCost, sellingPrice);    //Uses the method from the Store class to set the data values for the products.
        productChoice++;        
    }
    while (productChoice > MAXPRODUCTS)
    {
        System.out.println("The list is now full.");
        continueOption();
    }         
}//End of Method and Interface class

这是来自 Store 类的方法：

public boolean isAProduct(String product)
//Returns true if a name has been found otherwise returns false
{
    boolean found = false;
    int counter = 0;

    while (!found && (counter < MAXNUMBEROFPRODUCTS))
    {
        if (product.equalsIgnoreCase(product1.getName()))
        {
            found = true;
        }
        else if (product.equalsIgnoreCase(product2.getName()))
        {
            found = true;                 
        }
        else 
        {
            counter++;
        }            
    }        

    return found;
}//End of method

public void addProduct(String product)
//If isAProduct() returns false then the product name 
//entered by the user is stored in product1, product2 and product3 respectively

//!!!!I think this is where the problem originates but can't figure out why
{   
    if (numberOfProducts == 0) 
    //!!!!numberOfProducts has been declared as private int numberOfProducts=0;
    //I tried declaring numberOfProducts as a variable within addProduct()
    //but that just set the value to 0 each time and so only the name for product1 was set
    {
        product1.setName(product);
        numberOfProducts++;
    }
    else if (numberOfProducts == 1)
    {
        product2.setName(product);
        numberOfProducts++;
    }
    else if (numberOfProducts == 2)
    {                
        product3.setName(product);
    }            
    else
    {
        System.exit(0);
    }
} 

任何帮助或建议将不胜感激:)

干杯

Answer 1

while (!matesStore.isAProduct(name))
        //If a name has not been used, the name is added to the product
        {
            matesStore.addProduct(name); //!!!!I suspect the problem is this line.
        }       

第三个产品是无限循环的原因是因为你应该在这个语句中使用 If，while 也可以工作，但你看到有一个错误是由于你的方法 addProduct。如果您更改为 If it won't be an infinite loop 但是您的产品 3 将被窃听。

public boolean isAProduct(String product)
//Returns true if a name has been found otherwise returns false
{
    boolean found = false;
    int counter = 0;

    while (!found && (counter < MAXNUMBEROFPRODUCTS))
    {
        if (product.equalsIgnoreCase(product1.getName()))
        {
            found = true;
        }
        else if (product.equalsIgnoreCase(product2.getName()))
        {
            found = true;                 
        }
        else 
        {
            counter++;
        }            
    }        

    return found;
}//End of method

注意到您没有检查 product3，因此在搜索您的第 3 个产品名称时它总是返回 false。

!matesStore.isAProduct(name) = !false = true

维奥拉！！这就是while(true)，一个无限循环！

通过在您的 isAProduct() 方法中实现 product3.getName() 来修复。

你的代码很乱，你应该为产品使用数组，你可以用数组更好地搜索。

public boolean isAProduct(String product)
//Returns true if a name has been found otherwise returns false
{
    boolean found = false;
    int counter = 0;

    while (!found && (counter < MAXNUMBEROFPRODUCTS))
    {
        if (product.equalsIgnoreCase(product1.getName()))
        {
            found = true;
        }
        else if (product.equalsIgnoreCase(product2.getName()))
        {
            found = true;                 
        }
        else if (product.equalsIgnoreCase(product3.getName()))
        {
            found = true;                 
        }
        else 
        {
            counter++;
        }            
    }        

    return found;
}//End of method