我正在开发一个小型图书馆应用程序，允许用户存储，借阅，返回和删除技术手册。
我几乎完成了应用程序，现在我希望在用户从主菜单中选择选项1后，自动将库保存到外部txt文件，以查看整个库。我试图实现正确的代码，但现在没有创建任何文本文件。
以下是我手册课程中的相关代码：
if(Menu.menuChoice == 1 && Library.ManualList.size() > 0){
Library.displayManualList();
Menu.displayMenu();
try {
FileWriter fw = new FileWriter("Library.txt");
PrintWriter pw = new PrintWriter(fw);
pw.println(Library.ManualList);
pw.close();
} catch (IOException e) {
out.println("Error! Library unable to save.");
}
}
if(Menu.menuChoice == 1 && Library.ManualList.isEmpty()){
System.out.println(Messages.addManualFirst);
Menu.displayMenu();
}
如果需要，这是我的整个库类：
public class Library {
/** The Manual choice. */
public static int ManualChoice;
static String returnManualTitle;
/** The status1. */
static String status1 = "Available";
/** The status2. */
static String status2 = "Borrowed";
/** The Manual list. */
static ArrayList<Manual> ManualList = new ArrayList<Manual>();
static ArrayList<Manual> borrowedManuals = new ArrayList<Manual>();
/**
* Adds the Manual.
*/
static void addManual(){
Manual newManual = new Manual(); //create new Manual object with status "Available."
newManual.createManual();
ManualList.add(newManual);//add the Manual to the ManualList ArrayList.
System.out.println("\n\n--------------------------------------------------------------------------");
System.out.println("\n Manual added to library!\n");
System.out.println("--------------------------------------------------------------------------\n");
}
/**
* Display Manual list.
*/
static void displayManualList(){
if (ManualList.isEmpty()){//If the library is empty, it goes back to main menu and choice.
System.out.println("-------------------------------------------------------------");
System.out.println(Messages.empltyLibraryMessage + Messages.tryAgainMessage);
System.out.println("-------------------------------------------------------------");
Menu.menuChoice = 7;
} else {
System.out.printf("\n\nHere are the Manual/s currently stored in the library:\n\n\n");
for (int i = 0; i < ManualList.size(); i++){
System.out.printf("-------------------- Index Number: %s --------------------\n",i);
System.out.println(ManualList.get(i).displayManual());
System.out.println("---------------------------------------------------------\n");
}//End of For Loop.
}// End of Else Statement.
}//End of if Statement.
static void displayBorrowedManuals(){
if (ManualList.isEmpty()){//If the library is empty, it goes back to main menu and choice.
System.out.println("-------------------------------------------------------------");
System.out.println(Messages.empltyLibraryMessage + Messages.tryAgainMessage);
System.out.println("-------------------------------------------------------------");
Menu.menuChoice = 7;
} else {
for (int i = 0; i < borrowedManuals.size(); i++){
System.out.printf("-------------------- Index Number: %s --------------------\n",i);
System.out.println(borrowedManuals.get(i).displayManual());
System.out.println("---------------------------------------------------------");
}//End of For Loop.
}// End of Else Statement.
}//End of if Statement.
/**
* Borrow Manual.
*/
public static void borrowManual(){
if(ManualList.size() > 1){
displayManualList();
}
else if(ManualList.size() == 1){
ManualList.get(ManualChoice).status = "Borrowed";
ManualList.get(ManualChoice).borrower = User.userName;
ManualList.get(ManualChoice).borrowDate = "Today.";
ManualList.get(ManualChoice).returnDate = "In two weeks.";
borrowedManuals.add(ManualList.get(ManualChoice));
System.out.printf("\n\nThere is only 1 manual present in the library.\n\nBecause of this, it has been automatically borrowed for you.\n\nHere is the manual which has been borrowed:\n\n %s\n\n", ManualList.get(ManualChoice).displayManual());
System.out.println("Please return the Manual within two weeks!\n");
}
//register user's Manual choice.
ManualChoice = (Console.readInteger(Messages.enterManualIndexMessage, Messages.ManualIndexNotInListMessage, 0, Library.ManualList.size() - 1));
borrowLoop:
while(Menu.menuChoice == 3){
//Check if the Manual to be borrowed is available.
//ManualChoice = (Console.readInteger(Messages.enterManualIndexMessage, Messages.ManualIndexNotInListMessage, 1, Library.ManualList.size()));
if ((ManualList.get(ManualChoice).status.equalsIgnoreCase(status1)) && (ManualList.size() >= ManualChoice)){
//Print the borrowed Manual information and change the Manual status to borrowed.
ManualList.get(ManualChoice).status = "Borrowed";
ManualList.get(ManualChoice).borrower = User.userName;
ManualList.get(ManualChoice).borrowDate = "Today.";
ManualList.get(ManualChoice).returnDate = "In two weeks.";
//Add the borrowed Manual to the borrowedManuals arraylist:
borrowedManuals.add(ManualList.get(ManualChoice));
System.out.println("\n--------------------------------------------------------------------------");
System.out.println("\n Manual borrowed!\n");
System.out.println("--------------------------------------------------------------------------\n");
break borrowLoop;
}else if(ManualList.get(ManualChoice).status.equalsIgnoreCase(status2) && ManualList.size() >= ManualChoice){
System.out.println("\n--------------------------------------------------------------------------");
System.out.println("\n "
+ " The Manual you wish to borrow is already on loan.");
System.out.println("\n--------------------------------------------------------------------------\n");
break borrowLoop;
}else if(ManualChoice > ManualList.size()-1){
System.out.println(Messages.noSuchManualMessage);
break borrowLoop;
}
}
Menu.displayMenu();
}
/**
* Return Manual.
*/
static void returnManual(){
System.out.printf("\n\nHere are the Manual/s currently out on loan:\n\n");
if(borrowedManuals.size() > 0){
for (int i = 0; i < borrowedManuals.size(); i++)
System.out.println(borrowedManuals.get(i).displayManual());
returnManualTitle = Console.readString(Messages.enterManualSerial, Messages.tooShortMessage, 3);
}
int x = 0;
boolean serialExistance = false;
while (x < ManualList.size()){//Search for the Manual by title, if it exists change it's status,
//it's borrower and borrowDate.
if (ManualList.get(x).serial.equalsIgnoreCase(returnManualTitle)){
ManualList.get(x).status = "Available";
ManualList.get(x).borrower = "N/A";
ManualList.get(x).borrowDate = "N/A";
ManualList.get(x).returnDate = "N/A";
int p = 0;
while (p < borrowedManuals.size()) {
Manual borrowed = borrowedManuals.get(p); // guessing the name of this class
if (borrowed.serial.equalsIgnoreCase(returnManualTitle)) {
borrowedManuals.remove(p);
break;
}
p++;
}
System.out.println(Messages.successReturnMessage);
serialExistance = true;
break;//if a title is found, break out of the loop and display choice menu.
}
x = x+1;
}//end of while loop.
if(serialExistance == false){
boolean repeatReturnManual = Console.readYesNo("\n--------------------------------------------------------------------------" + "\n\nThe Manual with the title "+"\""+returnManualTitle +"\""+ " wasn't found!"
+"\n\nDo you want to try again? (Y/N):\n");
System.out.println("\n--------------------------------------------------------------------------");
if(repeatReturnManual){
returnManual();
}
}else if(serialExistance){
Menu.menuChoice = 7;
}
}
/**
* Removes the Manual.
*/
public static void removeManual(){
displayManualList();
ManualChoice = Console.readInteger(Messages.enterRemoveManualIndex ,Messages.ManualIndexNotInListMessage, 0, ManualList.size());
int p = 0;
while (p < borrowedManuals.size()){//Search for the Manual by title, if it exists change it's status,
//it's borrower and borrowDate.
if (borrowedManuals.get(p).title.equalsIgnoreCase(returnManualTitle)){
borrowedManuals.remove(p);
}
}
ManualList.remove(ManualChoice);
System.out.print(Messages.successRemovedManualMessages);
Menu.menuChoice = 7;
}
/**
* Empty library.
*/
static void emptyLibrary(){
System.out.println("\n WARNING!");
System.out.println("\n You have chosen to delete all Manuals in the library.\n");
System.out.println("--------------------------------------------------------------------------");
boolean emptyLibraryChoice = Console.readYesNo("\nAre you sure you wish to destroy the library? (Y/N): ");
System.out.println("\n--------------------------------------------------------------------------");
if(emptyLibraryChoice){
Library.ManualList.clear();
System.out.println(Messages.successEmptyLibraryMesssage);
System.out.println("--------------------------------------------------------------------------\n\n");
Menu.menuChoice = 7;
}
}
}
如果有人知道我怎么能将库的内容保存到文本文件请告诉我，任何帮助表示赞赏:)我是Java的新手，所以如果我遗漏了所需的代码请让我知道了！
答案 0 :(得分：0)
尝试循环以获取库的每个元素。
for(int i=0; i<Library.ManualList.size(); i++)
pw.println(Library.ManualLis.get(i));
pw.close();