我在Java类简介中的最后一项任务要求我们：
我已经完成了1-3次。如何让程序在.txt文件中加载信息？ （老实说，我不确定这是否是我老师在加载时的意思，因为我觉得这可能比我们过去的情况要复杂一些）
我已经能够让我的程序用记事本打开.txt文件，但我不知道如何让它读取整个文件和/或将文本信息保存到我的程序中。
import java.util.*;
import java.util.Scanner;
import java.io.*;
public class ArrayDemo_File {
private static Student[] StudentList = new Student[10];
private static FileWriter file;
private static PrintWriter output;
private static FileReader fr;
public static void StudentIndex() {
int index = 0;
while (index < StudentList.length) {
if(StudentList[index] != null) {
System.out.println(index + ": " + StudentList[index].getLName() + ", "
+ StudentList[index].getFName());
}
else {
return;
}
index++;
}
}
// View detailed data for Students listed in the index
public static void IndexData() {
int index = 0;
while (index < StudentList.length) {
if(StudentList[index] !=null) {
System.out.println(index + ": " + StudentList[index].getLName() + ", " + StudentList[index].getFName());
System.out.println("A Number: \t" + StudentList[index].getANum());
System.out.println("Address: \t" + StudentList[index].getAddress());
System.out.println();
}
else {
return;
}
index++;
}
}
// ADD STUDENT
public static void AddStudent() throws IOException {
// Memory
Student student = new Student();
Address address = new Address();
Scanner kb = new Scanner(System.in);
String last;
String frst;
int num;
int house;
String Street;
String City;
String State;
int Zip;
String Line2;
// Student Name and ID
System.out.println();
System.out.print("Last Name:\t");
last = kb.nextLine();
System.out.println();
System.out.print("First Name:\t");
frst = kb.nextLine();
System.out.println();
System.out.print("A Number:\tA");
num = kb.nextInt();
//Address
System.out.println();
System.out.print("What is your house number?\t");
house = kb.nextInt();
kb.nextLine();
System.out.println();
System.out.print("What is your Street's name?\t");
Street = kb.nextLine();
System.out.println();
System.out.print("What is your city?\t");
City = kb.nextLine();
System.out.println();
System.out.print("What is your State?\t");
State = kb.nextLine();
System.out.println();
System.out.print("What is your zip code?\t");
Zip = kb.nextInt();
kb.nextLine();
System.out.println();
System.out.print("Line 2: \t");
Line2 = kb.nextLine();
System.out.println("");
// Processing
address = new Address( house, Street, City, State, Zip, Line2 );
student = new Student(last, frst, num, address);
int index = 0;
while( index < StudentList.length ) {
if( StudentList[index] == null ) break;
index++;
}
StudentList[index] = student;
}
// REMOVE STUDENT
public static void RemoveStudent() {
System.out.println("Remove student");
int index = 0;
while (index < StudentList.length) {
if (StudentList[index] !=null) {
System.out.println(index + ": " + StudentList[index].getLName() + " " + StudentList[index].getFName());
}
index++;
}
Scanner kb = new Scanner(System.in);
int response;
System.out.println(" Please enter student number to remove or -1 to cancel removal");
System.out.print("\nInput: ");
response = Integer.parseInt(kb.nextLine());
if (response != -1) {
StudentList[response] = null;
}
Student[] StudentListTemp = new Student[10];
int nulls = 0;
for(int x = 0; x < StudentList.length; x++) {
if (StudentList[x] == null) {
nulls++;
}
else {
StudentListTemp[x - nulls] = StudentList[x];
}
}
StudentList = StudentListTemp;
}
public static void WriteFile() throws IOException {
String fileName;
Scanner kb = new Scanner(System.in);
System.out.println("Please enter a name for your file: ");
fileName = kb.nextLine();
output = new PrintWriter(fileName + ".txt");
for( int x = 0; x < StudentList.length; x++ ) {
if( StudentList[x] == null )
continue;
output.println( "[" + x + "]" );
output.println( StudentList[x].getFName() );
output.println( StudentList[x].getLName() );
output.println( StudentList[x].getAddress() );
}
output.close();
System.out.println("\n\tFile saved successfully!");
}
public static void loadFile() throws IOException {
Student student = new Student();
String fileName;
Scanner kb = new Scanner(System.in);
System.out.println("Please enter the name of the file: ");
fileName = kb.nextLine();
File file = new File(fileName + ".txt");
if(!file.exists()) {
System.err.println("\n\tError(404)): File Not Found!");
}
else {
System.out.println("\n\tFile found! It will now open!");
//FileReader fr = new FileReader(fileName + ".txt");
//System.out.println(fr);
ProcessBuilder pb = new ProcessBuilder("Notepad.exe", fileName + ".txt");
pb.start();
}
}
//CONSOLE MENU
public static void Menu() throws IOException {
Scanner kb = new Scanner(System.in);
int response;
boolean run = true;
while(run) {
System.out.println("--------------------------" );
System.out.println(" OPTIONS: ");
System.out.println(" 0) View Student Names ");
System.out.println(" 1) View Student details ");
System.out.println(" 2) Add Student ");
System.out.println(" 3) Remove Student ");
System.out.println(" 4) Save to File ");
System.out.println(" 5) Load File ");
System.out.println(" 6) Close Program ");
System.out.println("-------------------------- ");
System.out.print(" Choose an option: ");
response = Integer.parseInt(kb.nextLine());
System.out.println();
switch(response) {
case 0:
StudentIndex();
break;
case 1:
IndexData();
break;
case 2:
AddStudent();
break;
case 3:
RemoveStudent();
break;
case 4:
WriteFile();
break;
case 5:
loadFile();
break;
case 6:
run = false;
break;
default:
System.out.println(" ERROR: "+ response + " ! ");
}
}
System.out.println( "Have a nice day!" );
}
public static void main(String[] args) throws IOException {
// StudentList[0] = new Student("Doe", "Jon", 0000, new Address(00, "Road", "City", "State", 37343, "000"));
// StudentList[1] = new Student("Ricketts", "Caleb", 0001, new Address(000, "000", "000", "0000", 000, "000"));
// StudentList[2] = new Student("Smith", "Amanda", 2222, new Address(000, "000", "000", "000", 000, "000"));
// StudentList[3] = new Student("Wilson", "Judy", 3333, new Address(000, "000", "000", "000", 000, "000"));
Menu();
}
}
我尝试使用filereader来读取文件，但它没有输出任何内容。不确定我做错了什么。
答案 0 :(得分：0)
使用这些代码，您可以在SDCard中编写文本文件，同时需要在android manifest中设置权限：
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
在写文件之前还要检查你的SD卡是否已安装＆amp;您的外部存储状态是可写的
Environment.getExternalStorageState()
鳕鱼：
public void generateNoteOnSD(String sFileName, String sBody){
try
{
File root = new File(Environment.getExternalStorageDirectory(), "Notes");
if (!root.exists()) {
root.mkdirs();
}
File gpxfile = new File(root, sFileName);
FileWriter writer = new FileWriter(gpxfile);
writer.append(sBody);
writer.flush();
writer.close();
Toast.makeText(this, "Saved", Toast.LENGTH_SHORT).show();
}
catch(IOException e)
{
e.printStackTrace();
importError = e.getMessage();
iError();
}
}
Check the http://developer.android.com/guide/topics/data/data-storage.html
答案 1 :(得分：0)
扫描仪可以很好地阅读.txt文件。使用另一个Scanner对象来读取文件，一次一行。代码完成后，文件的每一行都将存储在列表中，每一行都在相应的索引处（例如：list.get（0）将返回第一行，list.get（1）返回第二行等）。
public static void loadFile()
{
Student student = new Student();
String fileName;
Scanner kb = new Scanner(System.in);
Scanner read;
ArrayList<String> list = new ArrayList<String>();
System.out.println("Please enter the name of the file: ");
fileName = kb.nextLine();
File file = new File(fileName + ".txt");
if(!file.exists())
{
System.err.println("\n\tError(404)): File Not Found!");
} else {
System.out.println("\n\tFile found! It will now open!");
read = new Scanner(file);
//FileReader fr = new FileReader(fileName + ".txt");
//System.out.println(fr);
//ProcessBuilder pb = new ProcessBuilder("Notepad.exe", fileName + ".txt");
//pb.start();
while(read.hasNextLine()) {
String currentLine = read.nextLine();
list.add(currentLine);
}
}
}