问题：productArray来自哪里：
for ( Product product : productArray )
＆安培;
Arrays.sort( productArray, new ProductComparator() );
问题：我做错了什么？我该怎么做？
昨天的相关Post
EDIT
::: EDIT ::: 好的，我在这里听取了你的建议
Product productArray[] = new Product[ARRAY_LENGTH]
现在它已经破了
/tmp/jc_22339/InventoryPart2.java:99: cannot find symbol
symbol : variable productArray
location: class InventoryPart2
for ( Product product : productArray ) {
^
/tmp/jc_22339/InventoryPart2.java:101: cannot find symbol
symbol : variable productArray
location: class InventoryPart2
inventoryValue += productArray.calcInventoryValue();
^
如果我这样做
for ( Product product : productArray[] ) {
我得到了
/tmp/jc_23524/InventoryPart2.java:69: '.class' expected
for ( Product product : productArray[] ) {
^
所以我被困了。
开始计划
:::更新代码:::
/**
This program stores a collection of a product and its variables in a java array
It will sort and display the information with a total
*/
// Import statements go here
import java.util.Scanner;// Import and use scanner
import java.util.Arrays;
public class InventoryPart2 {
/**
* @param args the command line arguments
*/
public static void main(String[] args) {// begin main
// Define your array of product objects and index here
final int ARRAY_LENGTH = 5;// declare constant
final int version = 2;// declare int version number
// Create instance of Scanner class
Scanner input = new Scanner( System.in );// new Scanner for CL input
// Set counter to loop x times to populate your array of product objects
int counter = 0;
// Initialize your product array with the number of objects to populate it with
Product productArray[] = new Product[ARRAY_LENGTH];// create array Product of class Product
// Welcome message
System.out.printf( "\n%s%d\n" ,
"Welcome to the Productentory Program v.", version );
// Construct default values for Product
productArray[0] = new Product("EThe Invisible Man", 0, 8.50);
productArray[1] = new Product("DThe Matrix", 1, 17.99);
productArray[2] = new Product("CSe7en", 7, 12.99);
productArray[3] = new Product("BOceans Eleven", 11, 9.99);
productArray[4] = new Product("AHitch Hikers Guide to the Galaxy", 42, 18.69);
/*// Loop as many times as your counter variable
{
// Instantiate a product object
// Prompt for product name and call the set method on your product object
// Prompt for item number and call the set method on your product object
// Prompt for units in stock and call the set method on your product object
// Prompt for unit price and call the set method on your product object
// store product object in array element
//Destroy product object reference
product = null;
// Flush the buffer
input.nextLine();
}*/
// Sort product array by product name using Comparator implementation class
sortProductArray();
// Print sorted array
for ( Product product : productArray[] ) {
if ( counter == 0 )
System.out.printf( "\n%s\n", "Sorted Inventory of DVD movies");
System.out.printf( "\n\n%s%d\n%s%s\n%s%d\n%s%,.2f\n%s%,.2f\n",
"Item Number: ",counter,
"DVD Title: ",productArray[counter].getProductTitle(),
"Copies in stock: ",productArray[counter].getUnitsInStock(),
"Price each disk: $",productArray[counter].getUnitPrice(),
"Value of disks: $",productArray[counter].calcInventoryValue());//End print
counter++;
if ( counter == productArray.length)// on last counter of loop print total
System.out.printf( "\n%s%,.2f\n\n\n",
"Collection Value: $",calcTotalInventoryValue());
}
// Calculate total Inventory value
}
// method to calculate the total Inventory value
private static double calcTotalInventoryValue()
{
double inventoryValue = 0;
// Iterate array of product objects and calculate total value of entire Inventory
for ( Product product : productArray ) {
// accumulate inventory value from each product object in array
inventoryValue += productArray.calcInventoryValue();
}
return totalInventoryValue;
} // end method calcInventoryValue
// method to sort product array
private static void sortProductArray()
{
Arrays.sort( productArray, new ProductComparator() );
} // end method calcInventoryValue
}
答案 0 :(得分：3)
此
Product Product[] = new Product[ARRAY_LENGTH];
应该是这样的：
Product productArray[] = new Product[ARRAY_LENGTH];
- 编辑
您还需要更改引用此“变量”的相关行。
如果我建议，如果您对此感到困惑，请让您的老师/书籍更新“变量”。
不要担心，如果你没有得到它：继续问，直到你这样做。如果你有足够的兴趣去学习，你就会被淘汰。所以要感兴趣，提出问题，做自己的研究，生活会很好。
答案 1 :(得分：1)
我认为“productArray”应该是指您创建的产品数组。所以就行：
Product Product[] = new Product[ARRAY_LENGTH];// create array Product of class Product
也改变它：
Product[] productArray = new Product[ARRAY_LENGTH];
答案 2 :(得分：1)
您必须拥有Product数组作为InventoryPart2类的成员或传递给sortProductArray方法。如果选择后者，则必须更改该方法以返回对已排序数组的引用。
您的Product数组位于静态main方法中，而不是对象的一部分，因此您遇到了问题。我建议你做这样的事情：
public class Inventory
{
private static final int DEFAULT_INVENTORY_SIZE = 5;
private Product [] products;
private int numProducts;
public Inventory()
{
this(DEFAULT_INVENTORY_SIZE);
}
public Inventory(int size)
{
products = new Product[size];
numProducts = 0;
}
public void addProduct(Product p)
{
products[numProducts++] = p;
}
public void sort()
{
// sort the array here
}
public String toString()
{
StringBuilder builder = new StringBuilder(1024);
// Create a string representation of you inventory here
return builder.toString();
}
}
面向对象编程是关于封装和信息隐藏。以这样的方式编写类，使客户不必知道或关心您是使用数组还是其他东西来保留产品。你在这里抽象出了库存的想法。
更新：
这是你的代码，只有更好并且正在运行：
import java.util.Scanner;
import java.util.Arrays;
public class InventoryPart2
{
public static void main(String[] args)
{
final int ARRAY_LENGTH = 5;
final int version = 2;
int counter = 0;
Product productArray[] = new Product[ARRAY_LENGTH];
System.out.printf("\n%s%d\n",
"Welcome to the Productentory Program v.", version);
productArray[0] = new Product("EThe Invisible Man", 0, 8.50);
productArray[1] = new Product("DThe Matrix", 1, 17.99);
productArray[2] = new Product("CSe7en", 7, 12.99);
productArray[3] = new Product("BOceans Eleven", 11, 9.99);
productArray[4] = new Product("AHitch Hikers Guide to the Galaxy", 42, 18.69);
productArray = sortProductArray(productArray);
// Print sorted array
for (Product product : productArray)
{
if (counter == 0)
{
System.out.printf("\n%s\n", "Sorted Inventory of DVD movies");
}
System.out.printf("\n\n%s%d\n%s%s\n%s%d\n%s%.2f\n%s%.2f\n",
"Item Number: ", counter,
"DVD Title: ", product.getProductTitle(),
"Copies in stock: ", product.getUnitsInStock(),
"Price each disk: $", product.getUnitPrice(),
"Value of disks: $", product.calcInventoryValue());
counter++;
}
System.out.printf("\n%s%,.2f\n\n\n",
"Collection Value: $", calcTotalInventoryValue(productArray));
}
private static double calcTotalInventoryValue(Product[] productArray)
{
double inventoryValue = 0;
for (Product product : productArray)
{
inventoryValue += product.calcInventoryValue();
}
return inventoryValue;
}
private static Product[] sortProductArray(Product[] productArray)
{
Arrays.sort(productArray, new ProductComparator());
return productArray;
}
}
我删除了您在任何地方添加的评论。他们只是杂乱无章;我建议你不要那样做了。通过使用更好的变量和方法名称，更好地使代码更具可读性和自我记录。
这仍然不是我建议您编写它的方式，但它有效。如果我不做太多修改，你就更有可能看到为什么会有效。
更新2：
万一你感兴趣，我的写作方式如下：
import java.util.Scanner;
import java.util.Arrays;
import java.text.NumberFormat;
public class Inventory
{
private static final int DEFAULT_LENGTH = 5;
private static final int VERSION = 2;
private Product[] products;
private int numProducts;
public static void main(String[] args)
{
Inventory inventory = new Inventory(5);
inventory.addProduct(new Product("EThe Invisible Man", 0, 8.50));
inventory.addProduct(new Product("DThe Matrix", 1, 17.99));
inventory.addProduct(new Product("CSe7en", 7, 12.99));
inventory.addProduct(new Product("BOceans Eleven", 11, 9.99));
inventory.addProduct(new Product("AHitch Hikers Guide to the Galaxy", 42, 18.69));
System.out.println(inventory);
System.out.println("total value: " + NumberFormat.getCurrencyInstance().format(inventory.getTotalValue()));
}
public Inventory()
{
this(DEFAULT_LENGTH);
}
public Inventory(int size)
{
products = new Product[size];
this.numProducts = 0;
}
public void addProduct(Product p)
{
products[numProducts++] = p;
}
public double getTotalValue()
{
double inventoryValue = 0.0;
for (Product product : products)
{
inventoryValue += product.calcInventoryValue();
}
return inventoryValue;
}
public String toString()
{
StringBuilder builder = new StringBuilder(1024);
String newline = System.getProperty("line.separator");
if (products.length > 0)
{
Arrays.sort(products, new ProductComparator());
for (Product product : products)
{
builder.append(product).append(newline);
}
}
return builder.toString();
}
}
答案 3 :(得分：0)
不要认为这里的每个人都能在几秒钟内发现语法错误。我们不是以这种方式出生的，我们只知道要寻找什么，因为我们犯了相同的错误数百次。
所以，如果你确信你想成为一名程序员，即使你因为这样的东西而在你的智慧结束时， 就会被删除。奉献和激情远比自然人才重要。
抬起头来。下次你遇到困难我们会在这里。 ：）