我正在尝试读取文本文件并将其存储在对象的arraylist中,但是我不断收到错误消息,说我无法将String转换为Item,这是我正在使用的arraylist类型。我尝试了各种解决方案,但不确定如何实现。我是编码新手,很快就要完成这项作业。有什么帮助!
private void loadFile(String FileName)
{
Scanner in;
Item line;
try
{
in = new Scanner(new File(FileName));
while (in.hasNext())
{
line = in.nextLine();
MyStore.add(line);
}
in.close();
}
catch (IOException e)
{
System.out.println("FILE NOT FOUND.");
}
}
我很抱歉没有添加Item类
public class Item
{
private int myId;
private int myInv;
//default constructor
public Item()
{
myId = 0;
myInv = 0;
}
//"normal" constructor
public Item(int id, int inv)
{
myId = id;
myInv = inv;
}
//copy constructor
public Item(Item OtherItem)
{
myId = OtherItem.getId();
myInv = OtherItem.getInv();
}
public int getId()
{
return myId;
}
public int getInv()
{
return myInv;
}
public int compareTo(Item Other)
{
int compare = 0;
if (myId > Other.getId())
{
compare = 1;
}
else if (myId < Other.getId())
{
compare = -1;
}
return compare;
}
public boolean equals(Item Other)
{
boolean equal = false;
if (myId == Other.getId())
{
equal = true;;
}
return equal;
}
public String toString()
{
String Result;
Result = String.format("%8d%8d", myId, myInv);
return Result;
}
}
这是我的阵列列表的创建。 私有ArrayList MyStore = new ArrayList();
这是我的文本文件的示例。
3679 87
196 60
12490 12
18618 14
2370 65
答案 0 :(得分:0)
in.nextLine()
返回一个String
。
因此,您无法将in.nextLine()
分配给Item
的实例。
您的代码可能需要将其更正为:
List<String> myStore = new ArrayList<String>();
private void loadFile(String FileName)
{
Scanner in;
try
{
in = new Scanner(new File(FileName));
while (in.hasNext())
{
myStore.add(in.nextLine());
}
in.close();
}
catch (IOException e)
{
System.out.println("FILE NOT FOUND.");
}
}
如果要在读取文件后获得Item
的列表,则需要提供将给定信息行转换为Item
实例的逻辑。
假设您的文件内容采用以下格式。
id1,inv1
id2,inv2
.
.
然后,您可以使用以下类型的Item
。
List<Item> myStore = new ArrayList<Item>();
private void loadFile(String FileName)
{
Scanner in;
String[] line;
try
{
in = new Scanner(new File(FileName));
while (in.hasNext())
{
line = in.nextLine().split(",");
myStore.add(new Item(line[0], line[1]));
}
in.close();
}
catch (IOException e)
{
System.out.println("FILE NOT FOUND.");
}
}
答案 1 :(得分:0)
/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package com.mycompany.rosmery;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
/**
*
* @author Sem-6-INGENIERIAINDU
*/
public class aaa {
public static void main(String arg[]) throws FileNotFoundException, IOException{
BufferedReader files=new BufferedReader(new FileReader(new File("")));
List<String> dto=new ArrayList<>();
String line;
while((line= files.readLine())!= null){
line= files.readLine();
dto.add(line);
//Hacer la logica para esos datos
}
}
}
答案 2 :(得分:0)
使用流的一种可能的解决方案(假设文件行中的数据用逗号分隔):
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;
public class Main {
public static void main(String[] args) throws IOException {
List<Item> items = loadFile("myfile.txt");
System.out.println(items);
}
private static List<Item> loadFile(String fileName) throws IOException {
try (Stream<String> stream = Files.lines(Paths.get(fileName))) {
return stream
.map(s -> Stream.of(s.split(",")).mapToInt(Integer::parseInt).toArray())
.map(i -> new Item(i[0], i[1]))
.collect(Collectors.toList());
}
}
}
或带有foreach:
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;
public class Main {
public static void main(String[] args) throws IOException {
List<Item> items = new ArrayList<>();
for (String line : loadFile("myfile.txt")) {
String[] data = line.split(",");
int id = Integer.parseInt(data[0]);
int inv = Integer.parseInt(data[1]);
items.add(new Item(id, inv));
}
System.out.println(items);
}
private static List<String> loadFile(String fileName) throws IOException {
try (Stream<String> stream = Files.lines(Paths.get(fileName))) {
return stream.collect(Collectors.toList());
}
}
}