用java将数据写入顺序文本文件
有一个文本文件“clients.txt”,包含以下内容:用java将数据写入顺序文本文件,java,validation,Java,Validation,有一个文本文件“clients.txt”,包含以下内容: 100 James Green 123.45 200 Sue Magenta 12345.67 它有两项记录。在第一条记录中,“100”是账号,“James”是姓,“Green”是姓,“123.45”是余额 下面的代码是“AccountRecord.java”文件,包含上述字段和例程set get方法: public class AccountRecord { private int account; private Str
100 James Green 123.45
200 Sue Magenta 12345.67
它有两项记录。在第一条记录中,“100”是账号,“James”是姓,“Green”是姓,“123.45”是余额
下面的代码是“AccountRecord.java”文件,包含上述字段和例程set get方法:
public class AccountRecord {
private int account;
private String firstName;
private String lastName;
private double balance;
// no-argument constructor calls other constructor with default values
public AccountRecord() {
this(0, "", "", 0.0); // call four-argument constructor
} // end no-argument AccountRecord constructor
// initialize a record
public AccountRecord(int acct, String first, String last, double bal) {
setAccount(acct);
setFirstName(first);
setLastName(last);
setBalance(bal);
} // end four-argument AccountRecord constructor
// set account number
public void setAccount(int acct) {
account = acct;
} // end method setAccount
// get account number
public int getAccount()
return account;
} // end method getAccount
// set first name
public void setFirstName(String first) {
firstName = first;
} // end method setFirstName
// get first name
public String getFirstName() {
return firstName;
} // end method getFirstName
// set last name
public void setLastName(String last) {
lastName = last;
} // end method setLastName
// get last name
public String getLastName() {
return lastName;
} // end method getLastName
//set balance
public void setBalance(double bal) {
balance = bal;
} // end method setBalance
// get balance
public double getBalance() {
return balance;
} // end method getBalance
} // end clas
下面的代码是“CreateTextFile.java”。它有一行代码:“output=newformatter(“clients.txt”);”,要从“clients.text”格式实例化格式化程序对象,请执行以下操作:
import java.io.FileNotFoundException;
import java.lang.SecurityException;
import java.util.Formatter;
import java.util.FormatterClosedException;
import java.util.NoSuchElementException;
import java.util.Scanner;
import com.deitel.ch17.AccountRecord;
public class CreateTextFile
{
private Formatter output; // object used to output text to file
// enable user to open file
public void openFile()
{
try
{
output = new Formatter( "clients.txt" ); // open the file
} // end try
catch ( SecurityException securityException )
{
System.err.println(
"You do not have write access to this file." );
System.exit( 1 ); // terminate the program
} // end catch
catch ( FileNotFoundException fileNotFoundException )
{
System.err.println( "Error opening or creating file." );
System.exit( 1 ); // terminate the program
} // end catch
} // end method openFile
// add records to file
public void addRecords()
{
// object to be written to file
AccountRecord record = new AccountRecord();
Scanner input = new Scanner( System.in );
System.out.printf( "%s\n%s\n%s\n%s\n\n",
"To terminate input, type the end-of-file indicator ",
"when you are prompted to enter input.",
"On UNIX/Linux/Mac OS X type <ctrl> d then press Enter",
"On Windows type <ctrl> z then press Enter" );
System.out.printf( "%s\n%s",
"Enter account number (> 0), first name, last name and balance.",
"? " );
while ( input.hasNext() ) // loop until end-of-file indicator
{
try // output values to file
{
// retrieve data to be output
record.setAccount( input.nextInt() ); // read account number
record.setFirstName( input.next() ); // read first name
record.setLastName( input.next() ); // read last name
record.setBalance( input.nextDouble() ); // read balance
if ( record.getAccount() > 0 )
{
// write new record
output.format( "%d %s %s %.2f\n", record.getAccount(),
record.getFirstName(), record.getLastName(),
record.getBalance() );
} // end if
else
{
System.out.println(
"Account number must be greater than 0." );
} // end else
} // end try
catch ( FormatterClosedException formatterClosedException )
{
System.err.println( "Error writing to file." );
return;
} // end catch
catch ( NoSuchElementException elementException )
{
System.err.println( "Invalid input. Please try again." );
input.nextLine(); // discard input so user can try again
} // end catch
System.out.printf( "%s %s\n%s", "Enter account number (>0),",
"first name, last name and balance.", "? " );
} // end while
} // end method addRecords
// close file
public void closeFile()
{
if ( output != null )
output.close();
} // end method closeFile
}
当我运行该类并尝试输入新记录时,我收到的消息如下:
run:
To terminate input, type the end-of-file indicator
when you are prompted to enter input.
On UNIX/Linux/Mac OS X type <ctrl> d then press Enter
On Windows type <ctrl> z then press Enter
Enter account number (> 0), first name, last name and balance.
? 300 Har Par 112.235
Enter account number (>0), first name, last name and balance.
? ^z
Invalid input. Please try again.
Enter account number (>0), first name, last name and balance.
?
运行:
要终止输入,请键入文件结束指示符
当系统提示您输入时。
在UNIX/Linux/Mac OS X上键入d,然后按Enter键
在Windows上键入z,然后按Enter键
输入帐号(>0)、名字、姓氏和余额。
? 300帕112.235
输入帐号(>0)、名字、姓氏和余额。
? ^Z
无效输入。请再试一次。
输入帐号(>0)、名字、姓氏和余额。
?
作为编程新手,我不明白为什么这个输入是无效的。我需要帮助来更正此代码或更正我的输入。整个代码已提交,以便能够对问题进行详细判断。我正在使用Netbean IDE 8.0和jdk-8u5-windows-64。编辑:修复错误
Ctrl+Z
不是windows下的防弹方法。您最好(因为帐号必须大于0)说:
要终止输入,请输入0并输入
。然后紧接着排队
record.setAccount( input.nextInt() ); // read account number
加
您要求人们浏览大量代码并找出问题所在。大多数代码与问题无关。只要包含重现问题所需的代码,就会有更多的人阅读您的问题。@DonBranson我想是因为输入提示说使用Ctrl+Z终止输入。尽管根据实际情况,在CMD中键入Ctrl+Z不会产生EOF。你是对的。在评论后看到了,并删除了我的评论。按CTRL-Z后,必须按enter键吗?还是在按下CTRL-Z后立即输出“无效输入,请重试”?你想让用户在按住CTRL-Z键后按enter键,还是应该退出?按CTRL-Z键时,文件“clients.txt”被清除,即所有记录都被删除,按enter键后输出“无效输入”。我已经添加了你的代码行。输入0并按enter键,我没有收到任何无效的输入消息。我成功地完成了构建,但是没有输出,并且清除了“clients.txt”的内容。请给我一些进一步的建议。@user3678356抱歉,我忘了用
==
替换
-更新后的Hi Serge Ballesta,伟大的!!!,你的回答让我成功了,程序输出正确,所有问题都解决了。
record.setAccount( input.nextInt() ); // read account number
if ( record.getAccount() == 0 ) { return; }