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();
             }
         }
     }

 }