JAVA自学笔记（8）—IO流

IO流（流？）

1.0 概念和分类

2.0 字节输出流

（1）输入一个字节

import java.io.FileOutputStream;
import java.io.IOException;

public class Main{
    public static void main(String[] args) throws IOException {
        FileOutputStream fos=new FileOutputStream("Demo01\\a.txt");
        fos.write(97);
        fos.close();
    }
}

　　

 

（2）多个字节的输入

import java.io.FileOutputStream;
import java.io.IOException;

public class Main{
    public static void main(String[] args) throws IOException {
        FileOutputStream fos=new FileOutputStream("Demo01\\b.txt");
        byte bytes[]={65,66,67,68};//ABCD
        //第一种
        fos.write(bytes);

        //第二种
        fos.write(bytes,1,3);

        //第三种

        String s="你好,很高兴认识你";
        byte[] bytes1 = s.getBytes();
        System.out.println(bytes1);//[B@1c53fd30
        fos.write(bytes1);

        fos.close();
    }
}

　　

字节输出流的续写和换行

import java.io.FileOutputStream;
import java.io.IOException;

public class Main{
    public static void main(String[] args) throws IOException {
        FileOutputStream fos=new FileOutputStream("Demo01\\c.txt",true);
        fos.write("我说很高兴我能遇见你".getBytes());
        for (int i = 0; i <5 ; i++) {
            fos.write("我也是".getBytes());
            fos.write("\r\n".getBytes());
        }
        fos.close();
    }
}

　

3.字节输入流

单个字符读取

 

import java.io.FileInputStream;
import java.io.IOException;

public class Main{
    public static void main(String[] args) throws IOException {
        FileInputStream fis=new FileInputStream("Demo01\\b.txt");
        int len=0;
        while((len=fis.read())!=-1)
        {
            System.out.print(len+" ");
        }
        fis.close();

    }
}

打印结果：

97 98 99 

 

多个字符的读取

 

import java.io.FileInputStream;
import java.io.IOException;

public class Main{
    public static void main(String[] args) throws IOException {
        FileInputStream fis=new FileInputStream("Demo01\\b.txt");
        byte []bytes=new byte[1024];
        int len=0;
        while((len=fis.read(bytes))!=-1)
        {
            System.out.println(len);
            String s = new String(bytes, 0, len);
            System.out.println(s);
        }

    }
}

打印结果：

8
ABCDEabc

4.字符输入流

import java.io.FileReader;
import java.io.IOException;

public class Main{
    public static void main(String[] args) throws IOException {
        FileReader fr=new FileReader("Demo01\\b.txt");
        int len=0;
        /*读取一个字符
        while ((len=fr.read())!=-1) {
            System.out.print((char)len);
        }*/


        /*读取多个字符
        char chars[]=new char[1024];
        while((len=fr.read(chars))!=-1)
        {
            System.out.println(new String(chars,0,len));
        }*/
        fr.close();
    }
}

5.字符输出流　

      

import java.io.FileWriter;
import java.io.IOException;

public class Main{
    public static void main(String[] args) throws IOException {
        FileWriter fw=new FileWriter("Demo01\\b.txt");
        fw.write(97);
        fw.flush();
        //fw.close();

    }
}

flush()和close()的区别

字节输出流的续写和换行

6.try...catch()处理流中的异常

import java.io.FileWriter;
import java.io.IOException;

public class Main{
    public static void main(String[] args) {
        FileWriter fs=null;
        try{
           fs=new FileWriter("Dem01\\b.txt");
            for(int i=0;i<5;i++)
            {
                fs.write("你好"+i+"\r\n");
            }
        }
        catch(IOException e)
        {
            System.out.println(e);
        }
        finally {
            if(fs!=null)
            {
                try {
                    fs.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }

        }

    }
}

　　

JDK 7对其优化

6.属性集

import java.util.Enumeration;
import java.util.Properties;
import java.util.Set;

public class Main{
    public static void main(String[] args) {
        Properties prop=new Properties();
        prop.setProperty("Jin","27");
        prop.setProperty("V","25");
        prop.setProperty("JK","25");

        Set<String> set = prop.stringPropertyNames();
        for (String s : set) {
            System.out.println(prop.get(s));
        }
    }
}

　　

store方法

import java.io.FileWriter;
import java.io.IOException;
import java.util.Enumeration;
import java.util.Properties;
import java.util.Set;

public class Main{
    public static void main(String[] args) throws IOException {
        Properties prop=new Properties();
        prop.setProperty("Jin","27");
        prop.setProperty("V","25");
        prop.setProperty("JK","23");
        prop.store(new FileWriter("Demo01\\b.txt"),"practice");
    }
}

load方法

import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.Properties;
import java.util.Set;

public class Main{
    public static void main(String[] args) throws IOException {
        Properties prop=new Properties();
        prop.load(new FileReader("Demo01\\b.txt"));
        Set<String> set = prop.stringPropertyNames();
        for (String s : set) {
            System.out.println(s+"="+prop.getProperty(s));
        }

    }
}

　

缓冲流　

1.0 字节缓冲输出流

2.字节缓冲输入流

  

import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.io.IOException;

public class Main{
    public static void main(String[] args) throws IOException {
        FileInputStream fis=new FileInputStream("Demo01\\c.txt");
        BufferedInputStream input=new BufferedInputStream(fis);
        int len=0;
        byte []bytes=new byte[1024];
        while((len=input.read(bytes))!=-1)
        {
            System.out.println(new String(bytes,0,len));
        }
        input.close();
    }
}

　

3.字符缓冲输出流

       

import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;

public class Main{
    public static void main(String[] args) throws IOException {
        BufferedWriter bw=new BufferedWriter(new FileWriter("Demo01\\c.txt"));
        for(int i=0;i<5;i++)
        {
            bw.write("你好，我叫赤木晴子");
            bw.newLine();
        }
        bw.flush();
        bw.close();

    }
}

　

打印结果:

4.字符缓冲输入流

           

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class Main{
    public static void main(String[] args) throws IOException {
        BufferedReader br=new BufferedReader(new FileReader("Demo01\\c.txt"));
        String s;
        while((s=br.readLine())!=null)
        {
            System.out.println(s);
        }
        br.close();
    }
}

　　

 转换流

1.0 OutputStreamWrite

2.InputStreamReader 

转换流的练习

将GBK文件转化为UTF-8文件

import java.io.*;

public class Main{
    public static void main(String[] args) throws IOException {
        InputStreamReader isr=new InputStreamReader(new FileInputStream("Demo01\\我是一个GBK文件.txt"),"GBK");
        OutputStreamWriter osw=new OutputStreamWriter(new FileOutputStream("Demo01\\转化后的UTF-8文件"),"UTF-8");

        int len=0;
        while((len=isr.read())!=-1)
        {
          osw.write(len);
        }
        isr.close();
        osw.close();
    }
}

　　

序列化与非序列化

序列化

ObjectOutputStream

     

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectOutputStream;

public class Main{
    public static void main(String[] args) throws IOException {
        ObjectOutputStream oos=new ObjectOutputStream(new FileOutputStream("Demo01\\a.txt"));

        oos.writeObject(new Person("百里玄策",18));

        oos.close();
    }
}

　　

ObjectInputStream

       

import java.io.FileInputStream;
import java.io.IOException;
import java.io.ObjectInputStream;

public class Main{
    public static void main(String[] args) throws IOException, ClassNotFoundException {
        ObjectInputStream ois=new ObjectInputStream(new FileInputStream("Demo01\\a.txt"));

        Object o = ois.readObject();

        ois.close();
        System.out.println(o);

    }
}

transient关键字修饰的成员变量不能被序列化（瞬态关键字）

import java.io.Serializable;

public class Person implements Serializable {
    private String name;
    private transient int age;

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

    public String getName() {
        return name;
    }

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

    public int getAge() {
        return age;
    }

    @Override
    public String toString() {
        return "Person{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }

    public void setAge(int age) {
        this.age = age;
    }

    public Person() {
    }
}

　　

import java.io.FileInputStream;
import java.io.IOException;
import java.io.ObjectInputStream;

public class Test {
    public static void main(String[] args) throws IOException,ClassNotFoundException {
        ObjectInputStream ois=new ObjectInputStream(new FileInputStream("Demo01\\a.txt"));
        Object o = ois.readObject();
        ois.close();
        System.out.println(o);

    }
}

打印结果：
Person{name='百里玄策', age=0}

打印流

   

import java.io.FileNotFoundException;
import java.io.PrintStream;

public class Main{
    public static void main(String[] args) throws FileNotFoundException {
        System.out.println("我在控制台输出"); 
        PrintStream ps=new PrintStream("输出流");
        System.setOut(ps);
        System.out.println("我在输出流中输出");
    }
}