java读写文件

总结整理一下Java文件操作的几种方式。无论哪种编程语言，文件读写操作时避免不了的一件事情，Java也不例外。Java读写文件一般是通过字节、字符和行三种方式来进行文件的操作。

import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.Reader;

public class FileUtil {

    /**
     * 按行读取文件
     */
    public static void ReadFileByLine(String filename) {
        File file = new File(filename);
        InputStream is = null;
        Reader reader = null;
        BufferedReader bufferedReader = null;
        try {
            is = new FileInputStream(file);
            reader = new InputStreamReader(is);
            bufferedReader = new BufferedReader(reader);
            String line = null;
            while ((line = bufferedReader.readLine()) != null) {
                System.out.println(line);
            }

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (null != bufferedReader)
                    bufferedReader.close();
                if (null != reader)
                    reader.close();
                if (null != is)
                    is.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    /**
     * 按字节读取文件
     * 
     * @param filename
     */
    public static void ReadFileByBytes(String filename) {
        File file = new File(filename);
        InputStream is = null;
        try {
            is = new FileInputStream(file);
            int index = 0;
            while (-1 != (index = is.read())) {
                System.out.write(index);
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } finally {
            try {
                if (null != is)
                    is.close();

            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        System.out.println("-----------------------------------");
        try {
            is = new FileInputStream(file);
            byte[] tempbyte = new byte[1000];
            int index = 0;
            while (-1 != (index = is.read(tempbyte))) {
                System.out.write(tempbyte, 0, index);
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } finally {
            try {
                if (null != is)
                    is.close();

            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    /**
     * 按字符读取文件
     * 
     * @param filename
     */
    public static void ReadFileByChar(String filename) {
        File file = new File(filename);
        InputStream is = null;
        Reader isr = null;
        try {
            is = new FileInputStream(file);
            isr = new InputStreamReader(is);
            int index = 0;
            while (-1 != (index = isr.read())) {
                System.out.print((char) index);
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (null != is)
                    is.close();
                if (null != isr)
                    isr.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    /**
     * 通过OutputStreamWriter写文件
     * 
     * @param filename
     */
    public static void Write2FileByOutputStream(String filename) {
        File file = new File(filename);
        FileOutputStream fos = null;
        // BufferedOutputStream bos = null;
        OutputStreamWriter osw = null;
        try {
            if (!file.exists()) {
                file.createNewFile();
            }
            fos = new FileOutputStream(file);
            osw = new OutputStreamWriter(fos);
            osw.write("Write2FileByOutputStream");
            // bos = new BufferedOutputStream(fos);
            // bos.write("Write2FileByOutputStream".getBytes());
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (null != osw) {
                try {
                    osw.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (null != fos) {
                try {
                    fos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    /**
     * 通过BufferedWriter写文件
     * 
     * @param filename
     */
    public static void Write2FileByBuffered(String filename) {
        File file = new File(filename);
        FileOutputStream fos = null;
        OutputStreamWriter osw = null;
        BufferedWriter bw = null;
        try {
            if (!file.exists()) {
                file.createNewFile();
            }
            fos = new FileOutputStream(file);
            osw = new OutputStreamWriter(fos);
            bw = new BufferedWriter(osw);
            bw.write("Write2FileByBuffered");
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (null != bw) {
                try {
                    bw.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (null != osw) {
                try {
                    osw.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (null != fos) {
                try {
                    fos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    /**
     * 通过FileWriter写文件
     * 
     * @param filename
     */
    public static void Write2FileByFileWriter(String filename) {
        File file = new File(filename);
        FileWriter fw = null;
        try {
            if (!file.exists()) {
                file.createNewFile();
            }
            fw = new FileWriter(file);
            fw.write("Write2FileByFileWriter");
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (null != fw) {
                try {
                    fw.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    public static void main(String[] args) {
        String filename = "D:/testfile.txt";
        // ReadFileByLine(filename);
        // ReadFileByBytes(filename);
        // ReadFileByChar(filename);
        String writeFile = "javawrite2file.txt";
        // Write2FileByOutputStream(writeFile);
        // Write2FileByBuffered(writeFile);
        Write2FileByFileWriter(writeFile);
    }
}

Java读写文件的大体情况应该就上面的几种方式，然而从效率的角度来讲。InputStream、OutputStream的效率比BufferedInputStream、BufferedOutputStream的效率要差，至于Reader、Writer没做进一步的比较。网上看到一些资料说Java.nio的效率最高，没有进一步做比较，不得而知了，等有时间再做进一步测试吧。

本文转载 https://www.cnblogs.com/rwxwsblog/p/4798855.html

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