java多种方式读写文件

main 函数：

import java.io.*;
import java.util.Vector;

import cn.com.test.byteio.ReadFromFile;
/*
  * 拷贝文件1 的内容到文件2 中（readFileByByte() ）, 文件可以是任何形式；
  * 除了按字节读写外，其他都用TXT 文件测试，只测试读，输出到console
  */
public class Byte_test {
    public static void main(String[] args){
         String filename = "F:\\jiegou.png";
        String filecopy = "F:\\copy.png";
        String filetxt = "F:\\111.txt";
        WriteToFile wtf = new WriteToFile();
        wtf.WriteByByte(filename, filecopy);
        ReadFromFile.readFileByBytes(filetxt);
        System.out.println(" ****************************** ");
        ReadFromFile.readFileByChars(filetxt);
        System.out.println(" ****************************** ");
        ReadFromFile.readFileByLines(filetxt);
        System.out.println(" ****************************** ");
        ReadFromFile.readFileByRandomAccess(filetxt);
    }
}

ReadFromFile 类，实现读取文件：

package cn.com.test.bytetest;
import java.io.*;

public class ReadFromFile{
    InputStream in = null ;
    public   ReadFromFile(String filename){
        in = this .getClass().getResourceAsStream(filename);
    }
    /*
     * 获取文件（读）的剩余可用长度AvailableByte(String filename)
     * return int
     * @param filename
     */
    @SuppressWarnings("finally")
    public static int AvailableByte(String filename){
        File file = new File(filename);
        int filelength = 0;
        try {
            InputStream is = new FileInputStream(file);
            filelength = is.available();
            System.out.println(" 文件长度："+filelength);       
         } catch (IOException e) {
            e.printStackTrace();
        } finally {
            return filelength;   
        }

    }
    /*
     * 按字节读取文件 ReadByByte(String filename)
     * 一次可以读取多个字节多用于图片、视频等非文本文档
     * @paramfilename
     */
    public   void readFileByByte(String filename){
       
        try {
            File file = new File(filename);
            InputStream in = null ;
            in = new FileInputStream(file);
            int count = 0,verdict = 0;
            count = ReadFromFile.AvailableByte(filename);
            byte [] sbyte = new byte [count];
            while ((verdict = in.read(sbyte)) != -1){
            System.out.write(sbyte,0,count);
            }
            } catch (IOException e) {
                e.printStackTrace();
             } finally {
                if (in != null ){
                    try {
                        in.close();
                    } catch (IOException e1) {
                    }
                }
            }
            System.out.println("*************");
        }
    /**
    * 以字符为单位读取文件readFileByChars(String fileName) ，
    * 常用于读文本，数字等类型的文件
    * @param fileName 文件名
    */
    public static void readFileByChars(String fileName){
        File file = new File(fileName);
        Reader reader = null ;
        try {
            System.out.println(" 以字符为单位读取文件内容，一次读一个字节：");
            // 一次读一个字符
            reader = new InputStreamReader( new FileInputStream(file));
            int tempchar;
            while ((tempchar = reader.read()) != -1){
             // 对于windows 下，rn 这两个字符在一起时，表示一个换行。
            // 但如果这两个字符分开显示时，会换两次行。
            // 因此，屏蔽掉r ，或者屏蔽n 。否则，将会多出很多空行。
            if ((( char )tempchar) != 'r'){
            System.out.print(( char )tempchar);
            }
            }
            reader.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
            System.out.println(" ");
        try {
            System.out.println(" 以字符为单位读取文件内容，一次读多个字节：");
            // 一次读多个字符
            char [] tempchars = new char [30];
            int charread = 0;
            reader = new InputStreamReader( new FileInputStream(fileName));
            // 读入多个字符到字符数组中，charread 为一次读取字符数
            while ((charread = reader.read(tempchars))!=-1){
            // 同样屏蔽掉r 不显示
            if ((charread == tempchars.length)&&(tempchars[tempchars.length-1] != 'r')){
            System.out.print(tempchars);
            } else {
            for ( int i=0; i<charread; i++){
            if (tempchars[i] == 'r'){
            continue ;
            } else {
            System.out.print(tempchars[i]);
            }
            }
            }
            }
           
            } catch (Exception e1) {
                e1.printStackTrace();
                } finally {
                    if (reader != null ){
                        try {
                            reader.close();
                        } catch (IOException e1) {
                        }
                    }
                System.out.println(" ");
                }
        }
    /**
     * 以行为单位读取文件readFileByLines(String fileName) ，
    * 常用于读面向行的格式化文件
    * @param fileName
    */
    public static void readFileByLines(String fileName){
        File file = new File(fileName);
        BufferedReader reader = null ;
        try {
             System.out.println(" 以行为单位读取文件内容，一次读一整行：");
            reader = new BufferedReader( new FileReader(file));
            String tempString = null ;
            int line = 1;
            // 一次读入一行，直到读入null 为文件结束
            while ((tempString = reader.readLine()) != null ){
            // 显示行号
            System.out.println("line " + line + ": " + tempString);
            line++;
            }
            reader.close();
            } catch (IOException e) {
                e.printStackTrace();
                } finally {
                    if (reader != null ){
                        try {
                            reader.close();
                        } catch (IOException e1) {
                        }
                    }
                    System.out.println(" ");
                }
        }
        /**
        * 随机读取文件内容readFileByRandomAccess
        * @param fileName
        */
        public static void readFileByRandomAccess(String fileName){
            RandomAccessFile randomFile = null ;
             try {
                System.out.println(" 随机读取一段文件内容：");
                // 打开一个随机访问文件流，按只读方式
                randomFile = new RandomAccessFile(fileName, "r");
                // 文件长度，字节数
                long fileLength = randomFile.length();
                 // 读文件的起始位置
                int beginIndex = (fileLength > 4) ? 4 : 0;
                // 将读文件的开始位置移到beginIndex 位置。
                randomFile.seek(beginIndex);
                byte [] bytes = new byte [10];
                int byteread = 0;
                 // 一次读10 个字节，如果文件内容不足10 个字节，则读剩下的字节。
                // 将一次读取的字节数赋给byteread
                while ((byteread = randomFile.read(bytes)) != -1){
                    System.out.write(bytes, 0, byteread);
                }
            } catch (IOException e){
                 e.printStackTrace();
            } finally {
                if (randomFile != null ){
                    try {
                        randomFile.close();
                    } catch (IOException e1) {
                    }
                }
            }
        }
       
    }

WriteToFile 类 ，实现拷贝功能：

package cn.com.test.bytetest;
import java.io.*;
public class WriteToFile {
    public OutputStream os = null ;
    public WriteToFile(){
   
    }
   
    public void WriteByByte(String filename1,String filename2){
        File filei = new File(filename2);
        File fileo = new File(filename1);
       
        int ver = 0;
        byte [] sbyte = new byte [1000];
       
        try {
            FileInputStream fis = new FileInputStream(fileo);
           
            FileOutputStream fos = new FileOutputStream(filei);
            while ((ver = fis.read(sbyte)) != -1){
                fos.write(sbyte, 0, ver);
                System.out.println(" 传输一段，长度1000");
             }
            if (fis!= null )fis.close();
            if (fos!= null )fos.close();
        } catch (IOException e){
            e.printStackTrace();
        }
       
       
       
    }
}

由于多种方式写文件是重复性工作，没有涉及；

API