div class="one_answers"的新手>啊，
我的实验室代码面临一些问题我已经进行了故障排除，发现我的文件阅读器/缓冲阅读器，车辆方法和链接列表值都没有问题
我发现我在使 if 语句工作时遇到问题我不知道如何比较从我的文件中提取的当前链接列表数据.txt使用标记器使用 if/else 的用户输入传递到给定字段？
主要方法
package test6;
// import packages
import java.util.LinkedList;
import java.io.*;
import java.util.Scanner;
import java.util.StringTokenizer;
public class Lab6 {
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
// TODO code application logic here
// Declare variables for reading file
FileReader fr = null;
BufferedReader br = null;
String inFile = "Vehicle_Records.txt";
final String INPUT_PROMPT = "nPlease enter the search word " + "that you would like to obtain more information on:";
String line;
StringTokenizer tokenizer;
// Declare variables to contain the record fields
String group;
String brand;
String model;
double rate;
// Declare and instantiate a new LinkedList
LinkedList<Vehicle> list = new LinkedList<Vehicle>();
try {
// Instantiate FileReader & BufferedReader objects
fr = new FileReader(inFile);
br = new BufferedReader(fr);
//read a line from the file
line = br.readLine();
// While line is not null
while (line != null) {
// Tokenize the records
tokenizer = new StringTokenizer(line, ",");
group = tokenizer.nextToken();
brand = tokenizer.nextToken();
model = tokenizer.nextToken();
rate = Double.parseDouble(tokenizer.nextToken());
// Create a new Vehicle object of the record
Vehicle newVehicle = new Vehicle(group, brand, model, rate);
System.out.println(newVehicle);
// Add this item object into the LinkedList
list.add(newVehicle);
// Read another line from file
line = br.readLine();
}
// Close BufferedReader
br.close();
}
catch (FileNotFoundException e)
{
System.out.println("The file" + inFile + "was not found");
}
catch (IOException e)
{
System.out.println("Reading error!" + e);
}
finally
{
//Check if FileReader is opened
if (fr != null) {
try {
//close FileReader
fr.close();
} catch (IOException e) {
System.out.println("Error closing file!");
}
}
}
// Print out the input prompt
System.out.println(INPUT_PROMPT);
try
{
// Create readers to read from user input
//FileReader ufr = new FileReader(INPUT_PROMPT);
BufferedReader ubr = new BufferedReader(new InputStreamReader (System.in));
// Read one line from user input
String uline=ubr.readLine();
// Loop through all the records in the LinkedList
for(int i = 0; i< list.size(); i++)
{
// if the record is the same as the input from user
// (Hint: use contains() in String class to check whether
// search word is found in the records
String temp = new String(uline);
if(list.get(i)== uline.contains(temp))
{
//print out the information of the vehicle that match user input
System.out.println(list.get(i));
}
}
}
catch(IOException e)
{
System.out.println(e);
}
catch (Exception e)
{
System.out.println("Input error!" + e);
}
}
}//main
车辆类
package lab6;
public class Vehicle {
// Declare all the variables to contain the fields of a record
String group;
String brand;
String model;
double rate;
// Creates a constructor to store all the fields into the variables
public Vehicle(String group, String brand, String model, double rate)
{
this.group=group; this.brand=brand; this.model=model; this.rate=rate;
}
// Create a toString() method to return string in the same delimited
// format as the input record
public String toString()
{
return(group+","+brand+","+model+","+rate);
}
}
您的代码不在方法内，因此您面临问题。
我假设，因为您通过车辆对象查看试图找到其四个变量之一的匹配项。您的方法是错误的，因为您将对象与字符串进行比较。
相反，您可以在 Vehicle 类中使用可比较接口，只需在其中比较多个字符串。
编辑：
public class Vehicle implements Comparable<String>{
/* This method returns 0 if the search matches
* Else it return a negative or a positive number*/
@Override
public int compareTo(String o) {
int cmp = this.getBrand().compareToIgnoreCase(o);
if(cmp == 0) return cmp;
cmp = this.getGroup().compareToIgnoreCase(o);
if(cmp == 0) return cmp;
cmp = this.getModel().compareToIgnoreCase(o);
if(cmp == 0) return cmp;
/* Edited this part to work with doubles */
try{
cmp = (int)(this.getRate() - Double.parseDouble(o));
}
catch(NumberFormatException e){
return cmp;
}
return cmp;
}
}
以下是您循环的方式：
for(int i = 0; i< list.size(); i++){
if(list.get(i).compareTo(uline) == 0)
{
System.out.println(list.get(i));
}
}
希望对您有所帮助。
附言。我也是这个:)<</p>
我终于和我的另一个朋友一起想通了不过，我还是要感谢你们所有人伸出援手来帮助我：'）
应在此处发布我的问题的解决方案
//-etc-
// Create readers to read from user input
//FileReader ufr = new FileReader(INPUT_PROMPT);
BufferedReader ubr = new BufferedReader(new InputStreamReader (System.in));
// Read one line from user input
String uline=ubr.readLine();
// Loop through all the records in the LinkedList
for(int i = 0; i< list.size(); i++)
{
// if the record is the same as the input from user
// (Hint: use contains() in String class to check whether
// search word is found in the records
Vehicle vehicle = list.get(i);
if(vehicle.group.contains(uline) ||
vehicle.brand.contains(uline) ||
vehicle.model.contains(uline))
{
//print out the information of the vehicle that match user input
System.out.println(list.get(i));
}