java IO 入门例子

import java.io.File;

/**
 * File类型基本操作
 */

/**
 * @author Administrator
 * 
 */
public class FileDemo {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        final String PATH = "c:\text.txt";
        File file = new File(PATH);
        if (file.exists()) {
            if (file.isFile()) {
                System.out.println("名称：" + file.getName());
                System.out.println("相对路径：" + file.getPath());
                System.out.println("绝对路径：" + file.getAbsolutePath());
                System.out.println("文件大小：" + file.length() + "字节");
            } else if (file.isDirectory()) {
                System.out.println("这是一个目录！");
            }
        } else {
            System.out.println("文件不存在！");
        }
    }

}

import java.io.FileInputStream;
import java.io.FileOutputStream;

/**
 * 使用字节流写入文件、读取文件。
 */
/**
 * @author Administrator
 * 
 */
public class ByteStreamDemo {

    /**
     * @param args
     * @throws Exception
     */
    public static void main(String[] args) throws Exception {
        // TODO Auto-generated method stub
        final String PATH = "c:\text.txt";
        
        FileOutputStream fos = null;
        try {
            String content = "王云鹏是帅哥！";
            byte[] contents = content.getBytes();
            fos = new FileOutputStream(PATH);
            fos.write(contents, 0, contents.length);
            fos.flush();
        } catch (Exception e) {
            // TODO: handle exception
            throw e;
        } finally {
            if (fos != null) {
                fos.close();
            }
        }
        
        FileInputStream fis = null;
        try {
            fis = new FileInputStream(PATH);
            int length = fis.available();
            byte[] contents = new byte[length];
            while(fis.read(contents, 0, length)!=-1){
                String content = new String(contents);
                System.out.println(content);
            }
        } catch (Exception e) {
            // TODO: handle exception
            throw e;
        }
        finally{
            if(fis!=null){
                fis.close();
            }
        }
    }

}

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.FileInputStream;
import java.io.FileOutputStream;

/**
 * 采用二进制流方式写入文件、读取文件。
 */

/**
 * @author Administrator
 * 
 */
public class BinaryStreamDemo2 {

    /**
     * @param args
     * @throws Exception
     */
    public static void main(String[] args) throws Exception {
        // TODO Auto-generated method stub
        final String PATH = "c:\text.txt";
        
        java.io.FileOutputStream fos = null;
        java.io.DataOutputStream dos = null;
        try {
            fos = new FileOutputStream(PATH);
            dos = new DataOutputStream(fos);

            dos.writeInt(1);
            dos.writeLong(2);
            dos.writeUTF("王云鹏是帅哥！");
            dos.flush();

        } catch (Exception e) {
            // TODO: handle exception
            throw e;
        } finally {
            if (dos != null) {
                dos.close();
            }
            if (fos != null) {
                fos.close();
            }
        }

        java.io.FileInputStream fis = null;
        java.io.DataInputStream dis = null;
        try {
            fis = new FileInputStream(PATH);
            dis = new DataInputStream(fis);

            int i = dis.readInt();
            long l = dis.readLong();
            String content = dis.readUTF();
            System.out.println(i);
            System.out.println(l);
            System.out.println(content);
        } catch (Exception e) {
            // TODO: handle exception
            throw e;
        } finally {
            if (dis != null) {
                dis.close();
            }
            if (fis != null) {
                fis.close();
            }
        }
    }

}

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.FileInputStream;
import java.io.FileOutputStream;

/**
 * 采用二进制流方式写入文件、读取文件。
 */

/**
 * @author Administrator
 *
 */
public class BinaryStreamDemo {

    /**
     * @param args
     * @throws Exception 
     */
    public static void main(String[] args) throws Exception {
        // TODO Auto-generated method stub
        java.io.FileOutputStream fos = null;
        java.io.DataOutputStream dos = null;
        java.io.FileInputStream fis = null;
        java.io.DataInputStream dis = null;
        try {
            fis = new FileInputStream("c:\source.jpg");
            dis = new DataInputStream(fis);
            
            fos = new FileOutputStream("c:\desc.jpg");
            dos = new DataOutputStream(fos);
            
            int temp = -1;
            while((temp=dis.read())!=-1){
                dos.write(temp);
            }
        } catch (Exception e) {
            // TODO: handle exception
            throw e;
        }
        finally
        {
            if(dos!=null)
            {
                dos.close();
            }
            if(fos!=null){
                fos.close();
            }
            if(dis!=null){
                dis.close();
            }
            if(fis!=null){
                fis.close();
            }
        }
        System.out.println("copy file success!");
    }

}

import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Arrays;

/**
 * 使用字符流写入文件、读取文件。
 */

/**
 * @author Administrator
 *
 */
public class CharStreamDemo {

    /**
     * @param args
     * @throws Exception 
     */
    public static void main(String[] args) throws Exception {
        // TODO Auto-generated method stub
        final String PATH = "c:\text.txt";
        
        FileWriter fw = null;
        try{
            fw = new FileWriter(PATH);
            fw.write("王云鹏是帅哥！");
            fw.flush();
        }catch(IOException ex){
            throw ex;
        }
        finally{
            if(fw!=null){
                fw.close();
            }
        }
        
        FileReader fr = null;
        try {
            fr = new FileReader(PATH);
            char[] chars = new char[1024];
            StringBuilder sb = new StringBuilder();
            int length = 0;
            while((length=fr.read(chars))!=-1){
                if(length==1024){
                    sb.append(chars);
                }else
                {
                    char[] less = Arrays.copyOf(chars, length);
                    sb.append(less);
                }
                Arrays.fill(chars, ' ');//清空数组
            }
            System.out.println(sb.toString());
            
        } catch (Exception e) {
            // TODO: handle exception
            throw e;
        }
        finally{
            if(fr!=null){
                fr.close();
            }
        }
    }

}

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileReader;
import java.io.FileWriter;

/**
 * 使用字符流+缓冲器写入文件、读取文件。
 */

/**
 * @author Administrator
 * 
 */
public class CharBufferStreamDemo {

    /**
     * @param args
     * @throws Exception
     */
    public static void main(String[] args) throws Exception {
        // TODO Auto-generated method stub
        final String PATH = "c:\text.txt";

        FileWriter fw = null;
        BufferedWriter bw = null;
        try {
            fw = new FileWriter(PATH);
            bw = new BufferedWriter(fw);
            bw.write("王云鹏是帅哥！");
            bw.newLine();
            bw.write("王云鹏是北大青鸟趟城中心的帅哥！");
            bw.flush();
        } catch (Exception e) {
            // TODO: handle exception
            throw e;
        } finally {
            if (bw != null) {
                bw.close();
            }
            if (fw != null) {
                fw.close();
            }
        }

        FileReader fr = null;
        BufferedReader br = null;
        try {
            fr = new FileReader(PATH);
            br = new BufferedReader(fr);
            String line = null;
            while ((line = br.readLine()) != null) {
                System.out.println(line);
            }
        } catch (Exception e) {
            // TODO: handle exception
            throw e;
        } finally {
            if (br != null) {
                br.close();
            }
            if (fr != null) {
                fr.close();
            }
        }
    }

}