初学，怎样文件读写

Question

java 的File api 不能操作文件内容，
如果想读到内容的话，可以考虑用InputStream, OutputStream,
如果是propertise文件，可以考虑用java.util.Properties的接口，按照key来读他的value

Answer 1

BufferedReader in = new BufferedReader(
                        new FileReader("file1")); DataOutputStream out = new DataOutputStream(
                           new BufferedOutputStream(
                               new FileOutputStream("file2")));String s = new String();
while((s = in.readLine()) != null)
    out.println(s);
in.close();
out.close();大概就是这个意思,当然异常自己捕捉了..

Answer 2

FileInputStream fi=new FileInputStream("yourinfilename");
FileOutputStream fo=new FileOutputStream("youroutfilename");
int temp;
while((temp=fi.read())!=-1){
   
     fo.write(temp);
}
fi.close();
fo.close();

Answer 3

package com.oaking.enterprisecredit.common.file;import java.io.*;public class MyFile extends File { /**
 * Constructor for MyFile
 */
public MyFile(String arg0) {
super(arg0);
} /**
 * Constructor for MyFile
 */
public MyFile(String arg0, String arg1) {
super(arg0, arg1);
} /**
 * Constructor for MyFile
 */
public MyFile(File arg0, String arg1) {
super(arg0, arg1);
} /**
 * create new file with new dir
 * return true if create new file sucess
 * return false if file already exits
 */
public boolean createNewFile() throws IOException
{
String path = this.getAbsolutePath();
if( ! this.exists() )
{
File parent = this.getAbsoluteFile().getParentFile();
if(parent.exists() || parent.mkdirs())
{
if(super.createNewFile())
{
return true;
}
}
return false;
}
return false;
}
/**
 * copy myself to another location
 */
public boolean copyFileToNewDir(String dir) throws IOException
{
MyFile newFile = new MyFile(dir);
newFile.createNewFile(); return true;
}
/**
 * copy from one fsName to fDName
 */
public static void CopyFiles(String fSName,String fDName)
{
File inFile = new File(fSName);
File outFile = new MyFile(fDName);
if (inFile.isDirectory())
{
outFile.mkdir();
File[] listFiles = inFile.listFiles();
for(int i = 0;i < listFiles.length;i ++)
{
String fileName1 = listFiles[i].getPath();
String fileName2 = outFile.getPath() + System.getProperty("file.separator") + listFiles[i].getName();
System.out.println(fileName1 + "      " + fileName2);
CopyFiles(fileName1,fileName2);
}
}
if (inFile.isFile())
{
try
{
DataInputStream in = new DataInputStream(
new BufferedInputStream(
new FileInputStream(inFile)));
DataOutputStream out;
if (outFile.exists())
{
out = new DataOutputStream(
new BufferedOutputStream(
new FileOutputStream(fDName)));
}
else
{
outFile.createNewFile();
out = new DataOutputStream(
new BufferedOutputStream(
new FileOutputStream(outFile)));
}
byte [] buf = new byte[1024];
int nums,offset=0;
while ((nums = in.read(buf,offset,1024)) != -1)
{
out.write(buf,offset,nums);
}
System.out.println("nums:" + nums);
out.close();
in.close();
}
catch (FileNotFoundException e)
{
System.out.println("File Not Find!");
}
catch (IOException e)
{
System.out.println(e.getMessage());
}
}
}        public static void moveFiles(String fSName,String fDName)
        {
                File inFile = new File(fSName);
                File outFile = new MyFile(fDName);
                if (inFile.isDirectory())
                {
                        outFile.mkdir();
                        File[] listFiles = inFile.listFiles();
                        for(int i = 0;i < listFiles.length;i ++)
                        {
                                String fileName1 = listFiles[i].getPath();
                                String fileName2 = outFile.getPath() + System.getProperty("file.separator") + listFiles[i].getName();
                                System.out.println(fileName1 + "      " + fileName2);
                                CopyFiles(fileName1,fileName2);
                        }                }
                if (inFile.isFile())
                {
                        try
                        {
                                DataInputStream in = new DataInputStream(
                                new BufferedInputStream(
                                new FileInputStream(inFile)));
                                DataOutputStream out;
                                if (outFile.exists())
                                {
                                        out = new DataOutputStream(
                                        new BufferedOutputStream(
                                        new FileOutputStream(fDName)));
                                }
                                else
                                {
                                        outFile.createNewFile();
                                        out = new DataOutputStream(
                                        new BufferedOutputStream(
                                        new FileOutputStream(outFile)));
                                }
                                byte [] buf = new byte[1024];
                                int nums,offset=0;
                                while ((nums = in.read(buf,offset,1024)) != -1)
                                {
                                        out.write(buf,offset,nums);
                                }
                                System.out.println("nums:" + nums);
                                out.close();
                                in.close();                        }
                        catch (FileNotFoundException e)
                        {
                                System.out.println("File Not Find!");
                        }
                        catch (IOException e)
                        {
                                System.out.println(e.getMessage());
                        }
                }
                inFile.delete();
}
}

Answer 4

public void readFile(String strFilePath)throws Exception
    {
        //get file
        File fileIn=new File(strFilePath);        BufferedReader bfr = null;        try
        {
            if(fileIn.exists())
            {
                //get BufferedReader from the file
                bfr=new BufferedReader(new FileReader(fileIn));
                //read one line of the file and make a String
                String strResult;
                while((strResult = bfr.readLine()) != null)
                {                    //call insertData to insert the data in string
                    System.out.println(strResult)
                }
                bfr.close();
            }
        }
        catch(DException ex)
        {
            logger.error("文件格式不正确");
            throw ex;
        }
        finally
        {
            if ( bfr != null )
            bfr.close();
        }    }

Answer 5

我是这么写的
class FileTrans {
public static void main(String[] args){
try{
//储存源文件和目标文件地址的变量
        String inStr="";
        String outStr=""; InputStreamReader ir = new InputStreamReader(System.in);
            BufferedReader in = new BufferedReader(ir); System.out.println("Please type any key to begin or quit");
String cmd = in.readLine();            System.out.println("Please Input The Source File Address");
            inStr = in.readLine();
            System.out.println("Please Output The Source File Address");
        outStr = in.readLine();
RandomAccessFile inFile = new RandomAccessFile(inStr,"r");
    RandomAccessFile outFile = new RandomAccessFile(outStr,"rw");
    String s = inFile.readLine();
    while(s != null)
{
    outFile.seek(outFile.length());
    outFile.writeBytes(s);
    s = inFile.readLine();
} System.out.println("quit");
    
                 
}
catch(IOException e){
        }
finally{
}
}
}源文件里有几行字母，而写到目标文件中所有字母都写在了一行，请问怎么回事啊