IO流（File类，IO流的分类，字节流和字符流，转换流，缓冲流，对象序列化）

1.File类

File类可以在程序中 操作文件和目录。File类是通过建立File类对象，在调用File类的对象来进行相关操作的。

示例：

public class Demo01 {

    public static void main(String[] args) {
        File f = new File("f:/我的歌声里.txt");
        //访问文件名相关
        String name = f.getName();
        System.out.println("文件名：" + name);
        String absolutePath = f.getAbsolutePath();
        System.out.println("绝对路径：" + absolutePath);
        String parent = f.getParent();
        System.out.println("父目录：" + parent);

        //检测相关
        System.out.println("是否存在：" + f.exists());
        System.out.println("是否可读" + f.canRead());
        System.out.println("是否可写：" + f.canWrite());

        //获取文件信息
        System.out.println("文件的大小： " + f.length());

        //以当前路径创建File对象
        File file = new File(".");
        String[] list = file.list();
        //遍历目录下的文件
        System.out.println();
        System.out.println("当前目录下有文件：");
        for(String name1:list){
            System.out.println(name1);
        }

    }

}

public class Demo01 {
public static void main(String[] args) {
	File f = new File("f:/我的歌声里.txt");
	//访问文件名相关
	String name = f.getName();
	System.out.println("文件名：" + name);
	String absolutePath = f.getAbsolutePath();
	System.out.println("绝对路径：" + absolutePath);
	String parent = f.getParent();
	System.out.println("父目录：" + parent);
	
    //检测相关
	System.out.println("是否存在：" + f.exists());
	System.out.println("是否可读" + f.canRead());
	System.out.println("是否可写：" + f.canWrite());
	
	//获取文件信息
	System.out.println("文件的大小： " + f.length());
	
	//以当前路径创建File对象
	File file = new File(".");
	String[] list = file.list();
	//遍历目录下的文件
	System.out.println();
	System.out.println("当前目录下有文件：");
	for(String name1:list){
		System.out.println(name1);
	}

}

}

运行结果：

2.IO流的分类

按照方向：输入流和输出流

按照流的大小：字节流和字符流

按照流的角色：节点流和处理流

流的类关系图如下：

3.字节流和字符流

字节流：FileInputStream 和 FileOutputStream

示例：把文件复制成另外的文件

public class Demo02 {

    public static void main(String[] args) throws IOException {
        /*
         * 需求把文件“我的歌声里.txt” 复制并改文件名为 “我的歌声里.java”
         *
         */
    //创建输入流
     InputStream is = new FileInputStream(new File("f:/我的歌声里.txt"));
     //创建输出流
     OutputStream os = new FileOutputStream(new File("f:/我的歌声里.java"));
     //创建接收字节数组
     byte[] bytes = new byte[1024];
     int len = 0;
     //循环输入输出
     while((len = is.read(bytes)) != -1 ){
         os.write(bytes, 0, len);
     }
     //关闭资源
     os.close();
     is.close();

    }

}

public class Demo02 {
public static void main(String[] args) throws IOException {
	/*
	 * 需求把文件“我的歌声里.txt” 复制并改文件名为 “我的歌声里.java”
	 * 
	 */
//创建输入流
 InputStream is = new FileInputStream(new File("f:/我的歌声里.txt"));
 //创建输出流
 OutputStream os = new FileOutputStream(new File("f:/我的歌声里.java"));
 //创建接收字节数组
 byte[] bytes = new byte[1024];
 int len = 0;
 //循环输入输出
 while((len = is.read(bytes)) != -1 ){
	 os.write(bytes, 0, len);
 }
 //关闭资源
 os.close();
 is.close();

}

}

运行结果：

字符流：FileReader和FileWriter

示例：切割文件

public class Demo03 {
    public static void main(String[] args) {
        FileReader r = null;
        FileWriter w = null;
        try {
            int count = 0;//定义一个标记
            int flag = 0;//文件名标记
            r = new FileReader("f:/我的歌声里.txt");
            w = new FileWriter("f:/我的歌声里" + flag +".txt");
            char[] chars = new char[10];
            int len = 0;
            while((len = r.read(chars)) != -1){
                System.out.println(new String(chars, 0, len));
                w.write(chars, 0, len);
                w.flush();
                count++;
                //定义切割的条件
                if(count >10 ){
                    flag++;
                    w = new FileWriter("f:/我的歌声里" + flag +".txt");
                    count = 0;
                }

            }

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally{
            try {
                w.close();
                r.close();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

        }


    }

}

public class Demo03 {
	public static void main(String[] args) {
		FileReader r = null;
	    FileWriter w = null;
		try {
			int count = 0;//定义一个标记
			int flag = 0;//文件名标记
			r = new FileReader("f:/我的歌声里.txt");
			w = new FileWriter("f:/我的歌声里" + flag +".txt");
			char[] chars = new char[10];
			int len = 0;
			while((len = r.read(chars)) != -1){
				System.out.println(new String(chars, 0, len));
				w.write(chars, 0, len);
				w.flush();
				count++;
				//定义切割的条件
				if(count >10 ){
					flag++;
					w = new FileWriter("f:/我的歌声里" + flag +".txt");
					count = 0;
				}
		}
		
	} catch (FileNotFoundException e) {
		e.printStackTrace();
	} catch (IOException e) {
		// TODO Auto-generated catch block
		e.printStackTrace();
	}finally{
		try {
			w.close();
			r.close();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
	}
	

}

}

运行结果

4.转换流

转换流：把字节流转换为字符流，一次来实现性能优化

       InputStreamReader 和 OutputStreamWriter

示例：

public class Demo04 {

    /**
     * @param args
     * @throws IOException
     */
    public static void main(String[] args) throws IOException {
        //键盘输入到文件
        InputStreamReader isr = new InputStreamReader(System.in);
        char[] chars = new char[1024];
        int len = 0;
        OutputStreamWriter osw = new OutputStreamWriter(new FileOutputStream("f:/我的文件.txt"));
        int count = 0;
        while((len = isr.read(chars)) != -1){
            osw.write(chars, 0, len);
            osw.flush();
            count++;
            if(count == 10){
                break;

            }
        }
        isr.close();
        osw.close();


    }

}

public class Demo04 {
/**
 * @param args
 * @throws IOException 
 */
public static void main(String[] args) throws IOException {
	//键盘输入到文件
	InputStreamReader isr = new InputStreamReader(System.in);
	char[] chars = new char[1024];
	int len = 0;
	OutputStreamWriter osw = new OutputStreamWriter(new FileOutputStream("f:/我的文件.txt"));
	int count = 0;
	while((len = isr.read(chars)) != -1){
	    osw.write(chars, 0, len);	
	    osw.flush();
	    count++;
	    if(count == 10){
	    	break;

	    }
	}
	isr.close();
	osw.close();
	

}

}

运行结果：

5.缓冲流

        把流读到缓冲区，然后再一次读到内存中来，以此来提高性能

        BuffererInputStream 和BufferedOutputStream

        BufferedReader 和 BufferedWriter

示例：

public static void main(String[] args) throws IOException {

        //读取并复制保存图片
        BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream("f:/qq.jpg")));
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(new FileOutputStream("f:/qqq.png")));

        String line = null;
        while((line = br.readLine()) != null){
            bw.write(line);
            bw.flush();
        }

        bw.close();
        br.close();

    }

	//读取并复制保存图片
	BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream("f:/qq.jpg")));
	BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(new FileOutputStream("f:/qqq.png")));
	
	String line = null;
	while((line = br.readLine()) != null){
	    bw.write(line);
	    bw.flush();
	}
	
	bw.close();
	br.close();

}</pre>
/**
 * @param args
 * @throws IOException 
 * @throws FileNotFoundException 
 * @throws ClassNotFoundException 
 */
public static void main(String[] args) throws FileNotFoundException, IOException, ClassNotFoundException {
	Student s1 = new Student("小红", 19);
	Student s2 = new Student("小白", 18);
	
	ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("f:/序列化.txt"));
	oos.writeObject(s1);
	oos.writeObject(s2);
	
	s2.setName("小白白");
	oos.writeObject(s2);//更改变量的属性，即使重新序列化也不会改变原属性值
	oos.close();
	
	ObjectInputStream ois = new ObjectInputStream(new FileInputStream("f:/序列化.txt"));
	Student rs1 = (Student) ois.readObject();
	Student rs2 = (Student) ois.readObject();
	System.out.println(rs1);
	System.out.println(rs2);


}
private String name;//学生姓名
private transient int age;//年龄设置为瞬时变量，将不被序列化


public Student(String name, int age) {
	super();
	this.name = name;
	this.age = age;
}



public String getName() {
	return name;
}



public void setName(String name) {
	this.name = name;
}



public int getAge() {
	return age;
}



public void setAge(int age) {
	this.age = age;
}
return "该学生的名字为：" + name + "，年龄为：" + age;