使用 BufferedWriter 打开文件
Opening File Using BufferedWriter
我是 Java 的初学者；我正在尝试将文本附加到先前使用 File class 创建的文本文件并使用 PrintWriter 写入文件。当我在 main class 中调用第一个方法时，文件已创建并可以使用。但是，当我调用第二种方法时 "try" 被调用，但没有新文本添加到 .txt 文件中。我把第二种方法放到一个单独的 public class 中，但我 运行 放到了同一个问题中。是否需要重新初始化fileName变量？
非常感谢。
package project;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Scanner;
public class WriteOut {
private int NumberOfMember;
private String ProjectName;
private String[] TeamMember;
public static String fileName;
private int[][] Vote;
public int FirstExport(int NumberOfMember, String ProjectName, String[] TeamMember) {
Scanner scan = new Scanner(System.in);
String fileName="ok"; //initializing the file name
System.out.println("Enter a file name to hold the Project:");
fileName = scan.nextLine( );
File fileObject = new File(fileName+".txt");
while (fileObject.exists( ))
{
System.out.println("There already is a file named "
+ fileName);
System.out.println("Enter a different file name:");
fileName = scan.nextLine( );
fileObject = new File(fileName+".txt");
}
PrintWriter outputStream = null;
try
{
outputStream =
new PrintWriter(new FileOutputStream(fileName+".txt"));
}
catch(FileNotFoundException e)
{
System.out.println("Error opening the file " + fileName +".txt");
System.exit(0);
}
for (int MemberCount = 1; MemberCount <= NumberOfMember; MemberCount ++) //For as long as the member count is less than the total number of members, the program will ask for the user input
{
//Statement of variable allocation to corresponding member position
outputStream.println("Team Member"+(MemberCount)+ ":"+TeamMember[MemberCount - 1]);
}
outputStream.println("Number of Members:"+ NumberOfMember+ "\nProject Name:"+ProjectName);
outputStream.close();
return NumberOfMember;
}
public int[][] SecondExport(int[][] Vote) {
System.out.println("hello"); //test to see if this is being called correctly
try
{
String content = "This is the content to write into file"; //Test content
BufferedWriter bw = new BufferedWriter(new FileWriter(fileName+".txt", true));
bw.append(content);
System.out.println("Done"); //Test to see if this is being called
bw.flush();
bw.close();
} catch (IOException e)
{
e.printStackTrace();
}
return Vote;
}
}
我的主要 class 在 EnterVotes() 方法下调用 WriteOut class：
package project:
import java.util.Scanner; //Importing the scanner tool
import java.util.stream.IntStream; //for summing arrays
import java.io.FileNotFoundException;
import java.text.DecimalFormat; //Importing the decimal tool
public class Project
{
public static void main(String[] args)
{
Project run = new Project();
run.StartMenu();
}
public static String option; //Declaring the strings representing the menu option buttons
private static int NumberOfMember; //Entering the number of members
public static int index=NumberOfMember; //used for later, declaring a square matrix
public static String[] TeamMember; //Declaring the strings representing the names of the members
public static int[][] Vote;
public static String ProjectName; // Declaring the project name variable as a string
private static boolean CorrectInput, ShowMenu; //Booleans CorrectInput, which determines whether the user has entered a valid input and ShowMenu, which determines whether the main menu is displayed again
public String fileName;
static Scanner scan = new Scanner(System.in); // Importing the scanner tool
DecimalFormat twoDecPlcFormatter = new DecimalFormat("0.00"); //Although not used currently, having a decimal formatter could come in handy later
//----------------------------------------------
//Declaration of StartMenu(): listing Menu Options and equalsIgnoreCase to accept either upper or lower case
//----------------------------------------------
Project(){
}
public void StartMenu()
{
Scanner scan = new Scanner(System.in);
System.out.println();
System.out.print("\nWelcome to Splitit ");
do
{
printMenu();
char input = scan.next().charAt(0); //Asking user to input a character
option = Character.toString(input); //Converting from characters to string
checkInput(option);
}
while (CorrectInput == false || ShowMenu == true); //Run StartMenu() while either the CorrectInput is false or ShowMenu is true
}
//----------------------------------------------
//Declaration of checkInput(String OneInput) method
//----------------------------------------------
private void checkInput(String OneInput)
{
if (OneInput.equalsIgnoreCase("A") == true)
{
About();
}
else if (OneInput.equalsIgnoreCase("C") == true)
{
CreateProjectTitle();
}
else if (OneInput.equalsIgnoreCase("V") == true)
{
EnterVotes();
}
else if (OneInput.equalsIgnoreCase("S") == true)
{
ShowProject();
}
else if (OneInput.equalsIgnoreCase("Q") == true)
{
Quit();
}
else
{
System.out.print("\tIncorrect input. "); //If the user has entered an incorrect input, force them to enter in correct input
CorrectInput = false;
}
}
private void printMenu()
{
System.out.println("\n\n\tAbout\t\t(A)");
System.out.println("\tCreate Project\t(C)");
System.out.println("\tEnter Votes\t(V)");
System.out.println("\tShow Project\t(S)");
System.out.println("\tQuit\t\t(Q)");
System.out.print("\n\tPlease choose an option: ");
}
//----------------------------------------------
//Declaration of About() method
//----------------------------------------------
public void About()
{
System.out.println("\tThis is a program designed to assign grades for a project based on each member's \n \tparticipation. ");
}
//----------------------------------------------
//Declaration of ShowProject()
//----------------------------------------------
public void ShowProject()
{
CorrectInput = true;
ShowMenu = true;
StoreVariables getThings = new StoreVariables();
System.out.println("Number of members: " + getThings.getNumberofMember(NumberOfMember));
System.out.println("Project name: " + getThings.getProjectName(ProjectName));
String[] abc = getThings.getTeamMember();
for (int Counter = 1; Counter <= NumberOfMember; Counter ++) //Returning each team member's name and corresponding member number
{
System.out.println("Name of member " + Counter + " : " + getTeamMemberName(Counter));
}
for (int Counter = 1; Counter <= NumberOfMember; Counter ++) //Returning each team member's name and corresponding member number
{
System.out.println("Votes for Member " + TeamMember[Counter-1] + " : ");
System.out.print(getThings.getVotes(Vote));
}
}
//----------------------------------------------
//Declaration of EnterVotes()
//----------------------------------------------
public int[][] EnterVotes()
{
CorrectInput=true;
Vote = new int [NumberOfMember][index];
index=NumberOfMember;
if (NumberOfMember==0) {
System.out.println("Please Create a Project Before Entering Votes!"); //Error Message
ShowMenu=true;
}
for (int row=0; row < Vote.length; row++)
{
System.out.println("Enter "+ TeamMember[row]+"'s votes, points must add up to 100:");
System.out.println();
for (int col=0; col < Vote[row].length; col++)
{
System.out.println("Enter "+TeamMember[row]+ "'s points for"+ TeamMember[col]+":");
Vote[row][col] = scan.nextInt();
}
}
//if (sum!=100){
//System.out.println("Error. Please make sure all votes add up to 100.");
//EnterVotes();
//}
sumRow(Vote, NumberOfMember);
return Vote;
}
public int[] sumRow(int[][] Vote, int NumberOfMember)
{
int sum[] = new int[NumberOfMember];
for (int i = 0; i < Vote.length; i++){
int total = 0;
for (int j = 0; j < Vote[0].length; j++)
total +=Vote[i][j];
sum[i] = total;}
for(int i = 1; i < sum.length; i++)
{
if (sum[i] != 100) {
System.out.println("Please Make Sure the points add to 100!");
EnterVotes();
}
}
WriteOut getsecond = new WriteOut();
getsecond.SecondExport(Vote);
return sum;
}
//----------------------------------------------
//Declaration of CreateProject()
//----------------------------------------------
public String CreateProjectTitle()
{
CorrectInput = true;
ShowMenu = true; //Still show Menu
System.out.print("\n\tEnter the project name: "); //Asking user for a project name
ProjectName = scan.next();
CreateProjectNumberofMembers(); //calling methods within the resulting methods
CreateProjectNamesofMembers();
return ProjectName;
}
public int CreateProjectNumberofMembers(){ //ENTER NUMBER OF TEAM MEMBERS
System.out.print("\tEnter the number of team members: "); //Asking user to input a number for all members count
NumberOfMember = scan.nextInt();
System.out.print("\n");
return NumberOfMember;
}
public String[] CreateProjectNamesofMembers(){
TeamMember = new String[NumberOfMember];
for (int MemberCount = 1; MemberCount <= NumberOfMember; MemberCount ++) //For as long as the member count is less than the total number of members, the program will ask for the user input
{
//Statement of variable allocation to corresponding member position
System.out.print("\tEnter the name of team member " + MemberCount + ": ");
TeamMember[MemberCount - 1] = scan.next();
}
WriteOut getThings2= new WriteOut();
getThings2.FirstExport(NumberOfMember, ProjectName, TeamMember);
System.out.print("Press any key to return to the main menu: ");
String DummyInput = scan.next(); //This is a dummy variable where the input is never used again
ShowMenu = true; //Irrespective of the input, the menu will be shown again by assigning this boolean to tr
return TeamMember;
}
//----------------------------------------------
//Declaration of Quit() method
//----------------------------------------------
public void Quit()
{
CorrectInput = true;
ShowMenu = false; //if ShowMenu is false, the program's menu will terminate
//WriteOut();
System.out.println("\tGoodbye. ");
scan.close();
}
//--------------------------------------------------------------------------------
//Declaration of toString() method to check for all variable values when necessary
//--------------------------------------------------------------------------------
private String getNumberOfMember()
{
return Integer.toString(NumberOfMember);
}
private String getProjectName(int NumberOfProjects)
{
return ProjectName;
}
private String getTeamMemberName(int index)
{
return TeamMember[index - 1];
}
}
您在 class WriteOut 中有一个字段：
public static String fileName;
然后 FirstExport 中的同名局部变量：
String fileName="ok"; //initializing the file name
局部变量在FirstExport内优先，进入SecondExport时字段为null。如果您只删除局部变量声明，您将得到我所理解的预期行为。
删除方法中的局部变量FirstExport:
String fileName="ok";
您只想使用您的 public 字段
public static String fileName;
因此您可以通过两种方法访问它。
我是 Java 的初学者；我正在尝试将文本附加到先前使用 File class 创建的文本文件并使用 PrintWriter 写入文件。当我在 main class 中调用第一个方法时，文件已创建并可以使用。但是，当我调用第二种方法时 "try" 被调用，但没有新文本添加到 .txt 文件中。我把第二种方法放到一个单独的 public class 中，但我 运行 放到了同一个问题中。是否需要重新初始化fileName变量？
非常感谢。
package project;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Scanner;
public class WriteOut {
private int NumberOfMember;
private String ProjectName;
private String[] TeamMember;
public static String fileName;
private int[][] Vote;
public int FirstExport(int NumberOfMember, String ProjectName, String[] TeamMember) {
Scanner scan = new Scanner(System.in);
String fileName="ok"; //initializing the file name
System.out.println("Enter a file name to hold the Project:");
fileName = scan.nextLine( );
File fileObject = new File(fileName+".txt");
while (fileObject.exists( ))
{
System.out.println("There already is a file named "
+ fileName);
System.out.println("Enter a different file name:");
fileName = scan.nextLine( );
fileObject = new File(fileName+".txt");
}
PrintWriter outputStream = null;
try
{
outputStream =
new PrintWriter(new FileOutputStream(fileName+".txt"));
}
catch(FileNotFoundException e)
{
System.out.println("Error opening the file " + fileName +".txt");
System.exit(0);
}
for (int MemberCount = 1; MemberCount <= NumberOfMember; MemberCount ++) //For as long as the member count is less than the total number of members, the program will ask for the user input
{
//Statement of variable allocation to corresponding member position
outputStream.println("Team Member"+(MemberCount)+ ":"+TeamMember[MemberCount - 1]);
}
outputStream.println("Number of Members:"+ NumberOfMember+ "\nProject Name:"+ProjectName);
outputStream.close();
return NumberOfMember;
}
public int[][] SecondExport(int[][] Vote) {
System.out.println("hello"); //test to see if this is being called correctly
try
{
String content = "This is the content to write into file"; //Test content
BufferedWriter bw = new BufferedWriter(new FileWriter(fileName+".txt", true));
bw.append(content);
System.out.println("Done"); //Test to see if this is being called
bw.flush();
bw.close();
} catch (IOException e)
{
e.printStackTrace();
}
return Vote;
}
}
我的主要 class 在 EnterVotes() 方法下调用 WriteOut class：
package project:
import java.util.Scanner; //Importing the scanner tool
import java.util.stream.IntStream; //for summing arrays
import java.io.FileNotFoundException;
import java.text.DecimalFormat; //Importing the decimal tool
public class Project
{
public static void main(String[] args)
{
Project run = new Project();
run.StartMenu();
}
public static String option; //Declaring the strings representing the menu option buttons
private static int NumberOfMember; //Entering the number of members
public static int index=NumberOfMember; //used for later, declaring a square matrix
public static String[] TeamMember; //Declaring the strings representing the names of the members
public static int[][] Vote;
public static String ProjectName; // Declaring the project name variable as a string
private static boolean CorrectInput, ShowMenu; //Booleans CorrectInput, which determines whether the user has entered a valid input and ShowMenu, which determines whether the main menu is displayed again
public String fileName;
static Scanner scan = new Scanner(System.in); // Importing the scanner tool
DecimalFormat twoDecPlcFormatter = new DecimalFormat("0.00"); //Although not used currently, having a decimal formatter could come in handy later
//----------------------------------------------
//Declaration of StartMenu(): listing Menu Options and equalsIgnoreCase to accept either upper or lower case
//----------------------------------------------
Project(){
}
public void StartMenu()
{
Scanner scan = new Scanner(System.in);
System.out.println();
System.out.print("\nWelcome to Splitit ");
do
{
printMenu();
char input = scan.next().charAt(0); //Asking user to input a character
option = Character.toString(input); //Converting from characters to string
checkInput(option);
}
while (CorrectInput == false || ShowMenu == true); //Run StartMenu() while either the CorrectInput is false or ShowMenu is true
}
//----------------------------------------------
//Declaration of checkInput(String OneInput) method
//----------------------------------------------
private void checkInput(String OneInput)
{
if (OneInput.equalsIgnoreCase("A") == true)
{
About();
}
else if (OneInput.equalsIgnoreCase("C") == true)
{
CreateProjectTitle();
}
else if (OneInput.equalsIgnoreCase("V") == true)
{
EnterVotes();
}
else if (OneInput.equalsIgnoreCase("S") == true)
{
ShowProject();
}
else if (OneInput.equalsIgnoreCase("Q") == true)
{
Quit();
}
else
{
System.out.print("\tIncorrect input. "); //If the user has entered an incorrect input, force them to enter in correct input
CorrectInput = false;
}
}
private void printMenu()
{
System.out.println("\n\n\tAbout\t\t(A)");
System.out.println("\tCreate Project\t(C)");
System.out.println("\tEnter Votes\t(V)");
System.out.println("\tShow Project\t(S)");
System.out.println("\tQuit\t\t(Q)");
System.out.print("\n\tPlease choose an option: ");
}
//----------------------------------------------
//Declaration of About() method
//----------------------------------------------
public void About()
{
System.out.println("\tThis is a program designed to assign grades for a project based on each member's \n \tparticipation. ");
}
//----------------------------------------------
//Declaration of ShowProject()
//----------------------------------------------
public void ShowProject()
{
CorrectInput = true;
ShowMenu = true;
StoreVariables getThings = new StoreVariables();
System.out.println("Number of members: " + getThings.getNumberofMember(NumberOfMember));
System.out.println("Project name: " + getThings.getProjectName(ProjectName));
String[] abc = getThings.getTeamMember();
for (int Counter = 1; Counter <= NumberOfMember; Counter ++) //Returning each team member's name and corresponding member number
{
System.out.println("Name of member " + Counter + " : " + getTeamMemberName(Counter));
}
for (int Counter = 1; Counter <= NumberOfMember; Counter ++) //Returning each team member's name and corresponding member number
{
System.out.println("Votes for Member " + TeamMember[Counter-1] + " : ");
System.out.print(getThings.getVotes(Vote));
}
}
//----------------------------------------------
//Declaration of EnterVotes()
//----------------------------------------------
public int[][] EnterVotes()
{
CorrectInput=true;
Vote = new int [NumberOfMember][index];
index=NumberOfMember;
if (NumberOfMember==0) {
System.out.println("Please Create a Project Before Entering Votes!"); //Error Message
ShowMenu=true;
}
for (int row=0; row < Vote.length; row++)
{
System.out.println("Enter "+ TeamMember[row]+"'s votes, points must add up to 100:");
System.out.println();
for (int col=0; col < Vote[row].length; col++)
{
System.out.println("Enter "+TeamMember[row]+ "'s points for"+ TeamMember[col]+":");
Vote[row][col] = scan.nextInt();
}
}
//if (sum!=100){
//System.out.println("Error. Please make sure all votes add up to 100.");
//EnterVotes();
//}
sumRow(Vote, NumberOfMember);
return Vote;
}
public int[] sumRow(int[][] Vote, int NumberOfMember)
{
int sum[] = new int[NumberOfMember];
for (int i = 0; i < Vote.length; i++){
int total = 0;
for (int j = 0; j < Vote[0].length; j++)
total +=Vote[i][j];
sum[i] = total;}
for(int i = 1; i < sum.length; i++)
{
if (sum[i] != 100) {
System.out.println("Please Make Sure the points add to 100!");
EnterVotes();
}
}
WriteOut getsecond = new WriteOut();
getsecond.SecondExport(Vote);
return sum;
}
//----------------------------------------------
//Declaration of CreateProject()
//----------------------------------------------
public String CreateProjectTitle()
{
CorrectInput = true;
ShowMenu = true; //Still show Menu
System.out.print("\n\tEnter the project name: "); //Asking user for a project name
ProjectName = scan.next();
CreateProjectNumberofMembers(); //calling methods within the resulting methods
CreateProjectNamesofMembers();
return ProjectName;
}
public int CreateProjectNumberofMembers(){ //ENTER NUMBER OF TEAM MEMBERS
System.out.print("\tEnter the number of team members: "); //Asking user to input a number for all members count
NumberOfMember = scan.nextInt();
System.out.print("\n");
return NumberOfMember;
}
public String[] CreateProjectNamesofMembers(){
TeamMember = new String[NumberOfMember];
for (int MemberCount = 1; MemberCount <= NumberOfMember; MemberCount ++) //For as long as the member count is less than the total number of members, the program will ask for the user input
{
//Statement of variable allocation to corresponding member position
System.out.print("\tEnter the name of team member " + MemberCount + ": ");
TeamMember[MemberCount - 1] = scan.next();
}
WriteOut getThings2= new WriteOut();
getThings2.FirstExport(NumberOfMember, ProjectName, TeamMember);
System.out.print("Press any key to return to the main menu: ");
String DummyInput = scan.next(); //This is a dummy variable where the input is never used again
ShowMenu = true; //Irrespective of the input, the menu will be shown again by assigning this boolean to tr
return TeamMember;
}
//----------------------------------------------
//Declaration of Quit() method
//----------------------------------------------
public void Quit()
{
CorrectInput = true;
ShowMenu = false; //if ShowMenu is false, the program's menu will terminate
//WriteOut();
System.out.println("\tGoodbye. ");
scan.close();
}
//--------------------------------------------------------------------------------
//Declaration of toString() method to check for all variable values when necessary
//--------------------------------------------------------------------------------
private String getNumberOfMember()
{
return Integer.toString(NumberOfMember);
}
private String getProjectName(int NumberOfProjects)
{
return ProjectName;
}
private String getTeamMemberName(int index)
{
return TeamMember[index - 1];
}
}
您在 class WriteOut 中有一个字段：
public static String fileName;
然后 FirstExport 中的同名局部变量：
String fileName="ok"; //initializing the file name
局部变量在FirstExport内优先，进入SecondExport时字段为null。如果您只删除局部变量声明，您将得到我所理解的预期行为。
删除方法中的局部变量FirstExport:
String fileName="ok";
您只想使用您的 public 字段
public static String fileName;
因此您可以通过两种方法访问它。