帮我看看这个问题啊....
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
// 注意类名要大写
public class Temp
{
public static void main(String [] args)
{
try
{
String head = "Name,ID,DS,DB ";
byte[] c = new byte[40];
c = head.getBytes();
System.out.println(new String(c));
String record = " ";
// 判断文件是否存在
File dir = new File( "c:\\student.txt ");
if(dir.exists())
{
// 是否有内容
FileInputStream infile = new FileInputStream(dir);
if(infile.read() < 0)
{
record = "Name ID DS DB " + "\r\n ";
}
infile.close();
}
BufferedWriter fo = new BufferedWriter(new FileWriter( "c:\\student.txt ",true));
String[] info = new String[4];
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
for (int i = 0; i < info.length; i++)
{
info[i] = reader.readLine();
record += info[i] + "\t\n ";
}
System.out.println(record);
fo.write(record);
// 换行
fo.write( "\r\n ");
fo.close();
}
catch (FileNotFoundException fe)
{
System.out.println( "File Not Found ");
}
catch (IOException ie)
{
System.out.println( "IO Exception ");
}
}
}
如果执行两次程序,你们想想会有什么结果呢,!就会出现两个HEAD变量的信息,应该怎么避免,还有我应该怎么解决空值问题
[解决办法]
我把你的代码,稍微改了一下,你看看行吗?
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
public class Temp {
public static void main(String[] args) {
// 每次需要输入的数量
final int COUNT = 2;
// 标题
final String HEAD = "Name,ID,DS,DB ";
// 文件名
final String FILENAME = "f:/student.txt ";
String record = " ";
File dir = new File(FILENAME);
if (!dir.exists()) {
record = HEAD + "\r\n ";
}
try {
BufferedWriter fo = new BufferedWriter(new FileWriter(FILENAME, true));
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
System.out.println(HEAD);
for (int i = 0; i < COUNT; i++) {
System.out.printf( "请输入第[%d]个数据: ", i+1);
String info = reader.readLine();
// 对输入的数据进行检验
if(!info.matches( ".+,\\d+,\\d+,\\d+ ")){
System.out.println( " ** 不符合规范,请重新输入** ");
i--;
}else{
record += info + "\r\n ";
}
}
System.out.println(record);
fo.write(record);
fo.close();
} catch (FileNotFoundException fe) {
System.out.println( "File Not Found ");
} catch (IOException ie) {
System.out.println( "IO Exception ");
}
}
}