关于写文件的问题(星期一结帖)
用流的方法写文件和读文件,请给个完整的例子!
(最好测试过可以用)
可用的话全分赠送.
[解决办法]
/**
@version 1.11 2004-05-11
@author Cay Horstmann
*/
import java.io.*;
import java.util.*;
public class RandomFileTest
{
public static void main(String[] args)
{
Employee[] staff = new Employee[3];
staff[0] = new Employee( "Carl Cracker ", 75000, 1987, 12, 15);
staff[1] = new Employee( "Harry Hacker ", 50000, 1989, 10, 1);
staff[2] = new Employee( "Tony Tester ", 40000, 1990, 3, 15);
try
{
// save all employee records to the file employee.dat
DataOutputStream out = new DataOutputStream(new FileOutputStream( "employee.dat "));
for (Employee e : staff)
e.writeData(out);
out.close();
// retrieve all records into a new array
RandomAccessFile in = new RandomAccessFile( "employee.dat ", "r ");
// compute the array size
int n = (int)(in.length() / Employee.RECORD_SIZE);
Employee[] newStaff = new Employee[n];
// read employees in reverse order
for (int i = n - 1; i > = 0; i--)
{
newStaff[i] = new Employee();
in.seek(i * Employee.RECORD_SIZE);
newStaff[i].readData(in);
}
in.close();
// print the newly read employee records
for (Employee e : newStaff)
System.out.println(e);
}
catch(IOException e)
{
e.printStackTrace();
}
}
}
class Employee
{
public Employee() {}
public Employee(String n, double s, int year, int month, int day)
{
name = n;
salary = s;
GregorianCalendar calendar = new GregorianCalendar(year, month - 1, day);
hireDay = calendar.getTime();
}
public String getName()
{
return name;
}
public double getSalary()
{
return salary;
}
public Date getHireDay()
{
return hireDay;
}
/**
Writes employee data to a data output
@param out the data output
*/
public void raiseSalary(double byPercent)
{
double raise = salary * byPercent / 100;
salary += raise;
}
public String toString()
{
return getClass().getName()
+ "[name= " + name
+ ",salary= " + salary
+ ",hireDay= " + hireDay
+ "] ";
}
/**
Writes employee data to a data output
@param out the data output
*/
public void writeData(DataOutput out) throws IOException
{
DataIO.writeFixedString(name, NAME_SIZE, out);
out.writeDouble(salary);
GregorianCalendar calendar = new GregorianCalendar();
calendar.setTime(hireDay);
out.writeInt(calendar.get(Calendar.YEAR));
out.writeInt(calendar.get(Calendar.MONTH) + 1);
out.writeInt(calendar.get(Calendar.DAY_OF_MONTH));
}
/**
Reads employee data from a data input
@param in the data input
*/
public void readData(DataInput in) throws IOException
{
name = DataIO.readFixedString(NAME_SIZE, in);
salary = in.readDouble();
int y = in.readInt();
int m = in.readInt();
int d = in.readInt();
GregorianCalendar calendar = new GregorianCalendar(y, m - 1, d);
hireDay = calendar.getTime();
}
public static final int NAME_SIZE = 40;
public static final int RECORD_SIZE = 2 * NAME_SIZE + 8 + 4 + 4 + 4;
private String name;
private double salary;
private Date hireDay;
}
class DataIO
{
public static String readFixedString(int size, DataInput in)
throws IOException
{
StringBuilder b = new StringBuilder(size);
int i = 0;
boolean more = true;
while (more && i < size)
{
char ch = in.readChar();
i++;
if (ch == 0) more = false;
else b.append(ch);
}
in.skipBytes(2 * (size - i));
return b.toString();
}
public static void writeFixedString(String s, int size, DataOutput out)
throws IOException
{
int i;
for (i = 0; i < size; i++)
{
char ch = 0;
if (i < s.length()) ch = s.charAt(i);
out.writeChar(ch);
}
}
}
[解决办法]
楼上的太麻烦的。。。
public void testIo() throws Exception{
File file=new File( "d:/file/src.txt "); //要读的文件
InputStream in=new FileInputStream(file);
FileOutputStream out=new FileOutputStream ( "d:/file/target.txt ");//要写入的文件
byte[] b=new byte[1024];
while((in.read(b))!=-1){ //等于-1说明文件已读完
out.write(b);//写入到文件
}
System.out.println( "success... ");
in.close();
out.close();
}
[解决办法]
不好意思上面那个是写修改前的,重新补充
//产生一个1000个5位以下的随机整数，并将它写如“rand.txt”内，之后输出这一千个数的最大最小值和平均值，并对这一千个数
//排序，保存在原文件中
import java.io.*;
class creat
{
public static void ct() throws IOException
{File f1=new File( "rand.txt ");
FileWriter fo=new FileWriter(f1);
BufferedWriter out=new BufferedWriter(fo);
for(int i=0;i <1000;i++)
{out.write(Integer.toString((int)(Math.random()*10000)));
out.newLine();
}
out.flush();
out.close();
fo.close();
}
};
class deal
{public static void aver() throws IOException
{ File f1=new File( "rand.txt ");
FileReader fr=new FileReader(f1);
BufferedReader bfr=new BufferedReader(fr);
String s;long sum=0;int max,min,n;
sum=max=min=Integer.parseInt(bfr.readLine());
while((s=bfr.readLine())!=null)
{n=Integer.parseInt(s);
sum=n+sum;
if(n> max) max=n;
if(n <min) min=n;
}
System.out.println( "最大值是： "+max);
System.out.println( "最小值是： "+min);
System.out.println( "平均数是： "+sum/1000);
fr.close();
bfr.close();}
public static void paixu() throws IOException
{File f1=new File( "rand.txt ");
File tempfile=new File( "temp.txt ");
FileReader fr1=new FileReader(f1);
BufferedReader bfr1=new BufferedReader(fr1);
FileWriter fr2=new FileWriter(tempfile);
BufferedWriter bfr2=new BufferedWriter(fr2);
String s=null;int a[]=new int[1000];int i=0,j=0,k=0;
while((s=bfr1.readLine())!=null)
{a[i]=Integer.parseInt(s);
i++;}
fr1.close();
bfr1.close();
f1.delete();
for(i=0;i <1000;i++)
for(j=0;j <1000-i-1;j++)
if(a[j]> a[j+1])
{k=a[j];
a[j]=a[j+1];
a[j+1]=k;
}
for(i=0;i <1000;i++)
{s=Integer.toString(a[i]);
bfr2.write(s);
bfr2.newLine();}
bfr2.flush();
bfr2.close();
fr2.close();
tempfile.renameTo(f1);
}
};
public class file
{public static void main(String args[])
{try{creat.ct();
deal.aver();
deal.paixu();}
catch(IOException e)
{}
}
}
