我的程序已完成。我需要的一件事是它处理空白行的方法。我读过其他帖子，但没有一个能帮助我将它们实现到我自己的代码中。我在读取文件的循环中尝试了各种语法，但没有一个有效。有人能帮助我吗。这看起来应该比现在感觉更容易。我正在尝试将其实现到我的代码中，但遇到困难。下面是我的两个类和 input.txt。照原样，该程序按预期运行。感谢您的帮助。
String line = in.nextLine();
while (line.length() == 0) {
if (in.hasNext()) {
line = in.nextLine();
} else {
break;
}
}
if (line.length() == 0) {
// reaches the end of input file
}
产品.java
/**
* Product
*
* A simple class framework used to demonstrate the design
* of Java classes.
*
* @author
* @version 02042015
*/
import java.util.*;
public class Product {
private String name;
private String code;
private int quantity;
private double price;
private String type;
private ArrayList<Integer> userRatings;
/*
* Product constructor
*/
public Product() {
name = "";
code = "";
quantity = 0;
price = 0.0;
type = "";
userRatings = new ArrayList<Integer>();
}
public Product(Product productObject) {
this.name = productObject.getName();
this.code = productObject.getInventoryCode();
this.quantity = productObject.getQuantity();
this.price = productObject.getPrice();
this.type = productObject.getType();
this.userRatings = new ArrayList<Integer>();
}
public Product(String name, String code, int quantity, double price, String type) {
this.name = name;
this.code = code;
this.quantity = quantity;
this.price = price;
this.type = type;
this.userRatings = new ArrayList<Integer>();
}
/*
* setName
* @param name - new name for the product
*/
public void setName(String name) {
this.name = name;
}
/*
* getName
* @return the name of the product
*/
public String getName() {
return name;
}
/*
* setType
* @param type - the type of the product
*/
public void setType(String type) {
this.type = type;
}
/*
* getType
* @return - the product type
*/
public String getType() {
return type;
}
/*
* setPrice
* @param price - the price of the product
*/
public void setPrice(double price) {
this.price = price;
}
/*
* getPrice
* @return the price of the product
*/
public double getPrice() {
return price;
}
/*
* setQuantity
* @param quantity - the number of this product in inventory
*/
public void setQuantity(int quantity) {
this.quantity = quantity;
}
/*
* getQuantity
* @return the number of this product in inventory
*/
public int getQuantity() {
return quantity;
}
/*
* setInventoryCode
* @param code - the new inventory code for the product
*/
public void setInventoryCode(String code) {
if(code.length()!= 8){
System.out.println("An invalid code has been entered. Please enter a code that is 8 characters in length.");
}
else{
}
this.code=code;
}
/*
* getInventoryCode
* @return the inventory code of the product
*/
public String getInventoryCode() {
return code;
}
/*
* setRatings
* @param code the new set of ratings for the product
*/
public void setRatings(ArrayList<Integer> Ratings){
this.userRatings = Ratings;
}
/*
* getRatings
* @return the ratings of the product
*/
public ArrayList<Integer> getRatings(){
return userRatings;
}
/*
* addUserRating
* NOTE: Each individual rating is stored with the product, so you need to maintain a list
* of user ratings. This method should append a new rating to the end of that list
* @param rating - the new rating to add to this product
*/
public void addUserRating(Integer rating1) {
if(rating1 > 5 || rating1 < 0){
System.out.println("You have entered an invalid rating. Please enter a rating between one and five stars.");
}
this.userRatings.add(rating1);
}
/*
* getUserRating
* NOTE: See note on addUserRating above. This method should be written to allow you
* to access an individual value from the list of user ratings
* @param index - the index of the rating we want to see
* @return the rating indexed by the value index
*/
public int getUserRating(int index) {
int a = this.userRatings.get(index);
return a;
}
/*
* getUserRatingCount
* NOTE: See note on addUserRating above. This method should be written to return
* the total number of ratings this product has associated with it
* @return the number of ratings associated with this product
*/
public int getUserRatingCount() {
int a = this.userRatings.size();
return a;
}
/*
* getAvgUserRating
* NOTE: see note on addUserRating above. This method should be written to compute
* the average user rating on demand from a stored list of ratings.
* @return the average rating for this product as a whole integer value (use integer math)
*/
public String getAvgUserRating() {
int sum = 0;
String avgRating = "";
if (userRatings.size() != 0){
for (int i = 0; i < this.userRatings.size(); i++) {
int a = getUserRating(i);
sum += a;
}
double avg = sum/this.userRatings.size();
if(avg >= 3.5){
avgRating = "****";
}
else if(avg >= 2.5){
avgRating = "***";
}
else if(avg >= 1.5){
avgRating = "**";
}
else if(avg >= 0.5){
avgRating = "*";
}
else{
}
}
else{
avgRating = "";
}
return avgRating;
}
}
Project02.java
/**
* Inventory Reporting Program
*
* A simple set of methods used to report and summarize
* the information read from an inventory file of product data
*
* @author
* @version 02042015
*/
import java.util.*;
import java.io.*;
public class Project02 {
public static void main(String[] args) {
//Establish the scanner so user input can be properly read.
Scanner keyboard = new Scanner(System.in);
System.out.print("Enter an inventory filename: ");
String fname = keyboard.nextLine();
ArrayList<Product> products = loadProducts(fname);
generateSummaryReport(products);
highestAvgRating(products);
lowestAvgRating(products);
largestTotalDollarAmount(products);
smallestTotalDollarAmount(products);
}
public static void generateSummaryReport (ArrayList<Product> Products){
int counter = 0;
System.out.println("Product Inventory Summary Report");
System.out.println("----------------------------------------------------------------------------------");
System.out.println();
System.out.printf("%-33s%-10s%-6s%-7s%-7s%-7s%-7s", "Product Name", "I Code", "Type", "Rating", "# Rat.", "Quant.", "Price");
System.out.println();
System.out.printf("%-33s%-10s%-6s%-7s%-7s%-7s%-7s", "-------------------------------", "---------", "----", "------", "------", "------", "------");
System.out.println();
while(counter < Products.size()){
System.out.printf("%-33s%-10s%-6s%-7s%6s%7s%7s", Products.get(counter).getName(), Products.get(counter).getInventoryCode(), Products.get(counter).getType(), Products.get(counter).getAvgUserRating(), Products.get(counter).getUserRatingCount(), Products.get(counter).getQuantity(), Products.get(counter).getPrice());
System.out.println();
counter++;
}
System.out.println("----------------------------------------------------------------------------------");
System.out.println("Total products in the database: " + Products.size());
}
/*
* loadProducts
* Given a filename, opens the file and reads Products from
* the file into an ArrayList of Product objects. Returns
* the ArrayList.
*
*
* @param fname - String containing the input file name
* @return - An ArrayList of Product objects
*/
public static ArrayList<Product> loadProducts(String fname) {
int a = 0;
Integer b = 0;
ArrayList<Product> products = new ArrayList<Product>();
try {
Scanner inFile = new Scanner(new File(fname));
while (inFile.hasNext()) {
int counter = 0;
String name = inFile.nextLine();
String code = inFile.nextLine();
int quantity = inFile.nextInt();
double price = inFile.nextDouble();
String type = inFile.next();
Product productObject = new Product(name, code, quantity, price, type);
while(inFile.hasNextInt() && counter==0){
a = inFile.nextInt();
if(a != -1){
b = new Integer(a);
productObject.addUserRating(b);
}
else{
counter = 1;
}
}
products.add(productObject);
if(inFile.hasNext()){
inFile.nextLine();
}
}
inFile.close();
}
catch (FileNotFoundException e) {
System.out.println("ERROR: " + e);
}
return products;
}
//Finds the item with the highest average user rating in stock
public static void highestAvgRating(ArrayList<Product> Products){
int counter = 0;
int a = 1;
while (counter <= Products.size()-1){
if(Products.get(counter).getAvgUserRating().length() > Products.get(a).getAvgUserRating().length()){
a = counter;
}
else{
}
counter++;
}
System.out.println("Highest Average User Rating In Stock: " + Products.get(a).getName() + " ("+Products.get(a).getAvgUserRating() + ")");
}
//Finds the item with the lowest average user rating in stock
public static void lowestAvgRating(ArrayList<Product> Products){
int counter = 0;
int a = 1;
while (counter <= Products.size()-1){
if(Products.get(counter).getAvgUserRating().length()<Products.get(a).getAvgUserRating().length()){
a=counter;
}
else{
}
counter++;
}
System.out.println("Lowest Average User Rating In Stock: "+Products.get(a).getName() + " ("+Products.get(a).getAvgUserRating() + ")");
}
//Finds the item with the largest total dollar amount in inventory (quantity * price)
public static void largestTotalDollarAmount(ArrayList<Product> Products){
int counter = 0;
int a = 1;
while (counter <= Products.size()-1){
if((Products.get(counter).getPrice())*(Products.get(counter).getQuantity()) > ((Products.get(a).getPrice())*(Products.get(a).getQuantity()))){
a=counter;
}
else{
}
counter++;
}
System.out.println("Item With The Largest Total Dollar Amount In Inventory: " + Products.get(a).getName() + " ($" + ((Products.get(a).getPrice())*(Products.get(a).getQuantity())) + ")");
}
//Finds the item with the smallest total dollar amount in inventory (quantity * price)
public static void smallestTotalDollarAmount(ArrayList<Product> Products){
int counter = 0;
int a = 1;
while (counter <= Products.size()-1){
if((Products.get(counter).getPrice())*(Products.get(counter).getQuantity()) < ((Products.get(a).getPrice())*(Products.get(a).getQuantity()))){
a=counter;
}
else{
}
counter++;
}
System.out.println("Item With The Smallest Total Dollar Amount In Inventory: " + Products.get(a).getName() + " ($" + ((Products.get(a).getPrice())*(Products.get(a).getQuantity())) + ")");
}
}
输入.txt
The Shawshank Redemption
C0000001
100
19.95
DVD
4
5
3
1
-1
The Dark Knight
C0000003
50
19.95
DVD
5
2
3
-1
Casablanca
C0000007
137
9.95
DVD
5
4
5
3
-1
The Girl With The Dragon Tattoo
C0000015
150
14.95
Book
4
4
2
-1
Vertigo
C0000023
55
9.95
DVD
5
5
3
5
2
4
-1
A Game of Thrones
C0000019
100
8.95
Book
-1
最佳答案
当你分解你的问题时，你会发现有两个主要问题:
- 逐行读取输入
- 跳过空行。
第一个问题可以通过 while (in.hasNext) in.nextLine() 解决。要解决第二个问题，只需在发现该行为空时添加继续:
while (in.hasNextLine()) {
line = in.nextLine();
// skip blank lines
if (line.length() == 0) continue;
// do your magic
}
现在，如何将其放入您的主程序中？如果我们能以某种方式做到这一点那就太好了:inFile.nextNonBlankLine()，对吧？因此，让我们创建自己的具有该方法的扫描仪!
首先，我们想如何使用自己的扫描仪？一个例子可能是:
SkipBlankScanner in = new SkipBlankScanner(inFile);
while (in.hasNextNonBlankLine()) {
line = in.nextNonBlankLine();
}
不幸的是，Scanner 是一个final 类，因此我们无法扩展它来添加我们的功能。下一个最好的办法是使用委托(delegate):
public class SkipBlankScanner {
private Scanner delegate;
private String line;
public SkipBlankScanner(Scanner delegate) {
this.delegate = delegate;
}
public boolean hasNextNonBlankLine() {
while (delegate.hasNextLine())
// return true as soon as we find a non-blank line:
if ((line = delegate.nextLine()).length > 0)
return true;
// We've reached the end and didn't find any non-blank line:
return false;
}
public String nextNonBlankLine() {
String result = line;
// in case we didn't call "hasNextNonBlankLine" before:
if (result == null && hasNextNonBlankLine())
result = line;
// try to read past the end:
if (result == null) throw new IllegalStateException();
line = null;
return result;
}
}
现在你就拥有了，你自己的扫描仪将忽略空白行!
您可以更进一步，创建一个扫描仪来扫描整个产品，例如(使用一些 Java-8):
public class ProductScanner {
private SkipBlankScanner scanner;
private Product product;
public ProductScanner(SkipBlankScanner scanner) {
this.scanner = scanner;
}
public boolean hasNextProduct() {
Product next = new Product();
if (fill(line -> next.setTitle(line)) &&
fill(line -> next.setInventoryCode(line)) &&
fill(line -> next.setQuantity(Integer.parseInt(line))) &&
fill(line -> next.setPrice(Double.parseDouble(line))) &&
fill(line -> next.setType(line))) {
try {
while (scanner.hasNextNonBlankLine() {
int rating = Integer.parseInt(scanner.nextNonBlankLine());
if (rating < 0) {
product = next;
return true;
}
next.addUserRating(rating);
}
} catch (NumberFormatException e) {
}
}
return false;
}
private boolean fill(Consumer<String> action) {
if (scanner.hasNextNonBlankLine() {
try {
action.accept(scanner.nextNonBlankLine());
return true;
} catch (Exception e) {
}
}
return false;
}
public Product nextProduct() {
Product result = product;
if (result == null && hasNextProduct())
result = product;
if (result == null)
throw new IllegalStateException();
product = null;
return result;
}
}
关于java - 使用 txt 输入文件和扫描仪处理空行，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/28312982/