Java学习——IO流

代码：

package Filetest;

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

public class Test1_CopyFile {
    public static void main(String[] args) {
        FileInputStream fis = null;
        FileOutputStream fos = null;
        try {
            fis  = new FileInputStream("a.txt");
            fos = new FileOutputStream("b.txt");
            int i;
            while ((i = fis.read()) !=-1){
            	System.out.println((char)i);
                fos.write(i);
            }

        }catch (Exception e){
            e.printStackTrace();
        }finally {
            try {
                if(fis != null){
                    fis.close();
                }
            }catch (Exception e){
                e.printStackTrace();
            }
            try {
                if(fos != null){
                    fos.close();
                }
            }catch (Exception e){
                e.printStackTrace();
            }
        }
    }
}

package test;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

public class Test2_CopyFile {
    
    public static void main(String[] args) throws IOException {
        FileInputStream fis = new FileInputStream("a.txt");
        FileOutputStream fos = new FileOutputStream("b.txt");
        byte[] bytes = new byte[1024];
        int len;
        while ((len = fis.read(bytes)) != -1){
            fos.write(bytes,0 ,len);
        }
        fis.close();
        fos.close();

    }
}

可以用指定编码表去读取数据，解决乱码问题

读：

package test;

import java.io.*;

public class Demo1_InputStreamReader {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream("b.txt"),"utf-8"));
        String line = br.readLine();
        System.out.println(line);
        br.close();
    }
}

写：

package test;

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

public class Demo2_OutputStreamWriter {
    public static void main(String[] args) throws IOException {
        OutputStreamWriter osw = new OutputStreamWriter(new FileOutputStream("c.txt"),"utf-8");
        osw.write("你好你好");
        osw.close();
    }
}

IDEA快捷键：

Ctrl + Alt + M ——> 抽取方法

Alt + Shift ——> 转换成Lambda表达式

输入iter + Tab ——> 生成foreach代码

package test;
import java.io.File;
import java.util.Arrays;
public class FileMethod {
    
    public static void main(String[] args) {
        printFile(new File("E:\课本"));

    }
    //递归遍历文件夹：获取一个文件夹下所有的文件名称，包含子文件夹
    public static void printFile(File dir){
        //1. 获取传入文件夹下的所有文件和文件夹对象
        File[] files  =dir.listFiles();
        //2. 遍历数组，获取每一个文件和文件夹对象
        for (File file : files) {
            if (file.isFile()){
                System.out.println(file.getName());
            }else if (file.isDirectory()){
                if (file.listFiles() != null){
                    printFile(file);
                }
            }
        }
    }

    private static void method2() {
        File f = new File("E:");
        if (f.isDirectory()){
            String[] sArr = f.list((dir, name) -> name.endsWith(".txt"));
            Arrays.stream(sArr).forEach(System.out::println);
        }
    }

    private static void method1() {
        File f = new File("E:");
        if (f.isDirectory()){
            String[] sArr  = f.list();
            Arrays.stream(sArr).forEach(System.out::println);
        }
    }


}

package test;
import java.io.IOException;
import java.io.RandomAccessFile;

public class Test_raf {
    public static void main(String[] args) throws IOException {
        RandomAccessFile raf  = new RandomAccessFile("config.txt","rw");
        int num = Integer.parseInt(raf.readLine())-1;
        if (num > 0){
            System.out.println("您还有"+ num + "次使用机会");
            raf.seek(0);
            raf.write((num+"").getBytes());
        }else {
            System.out.println("您的使用次数已到达上限，请购买正版");
        }
        raf.close();
    }
}

package test;

import java.io.*;

public class Demo1_ObjectStream {
    public static void main(String[] args) throws Exception {
        ObjectInputStream ois = new ObjectInputStream(new FileInputStream("a.txt"));
        Object object = ois.readObject();
        System.out.println(object);
    }

    private static void method() throws IOException {
        ObjectOutputStream oos  = new ObjectOutputStream(new FileOutputStream("a.txt"));
        Person p =  new Person("张三",23);
        oos.writeObject(p);
        oos.close();
    }

}

package test;
import java.io.Serializable;
public class Person implements Serializable {
    private static final long seriaLVersionUID  = 1L;
    private String name;
    private int age;

    public String getName() {
        return name;
    }

    public int getAge() {
        return age;
    }

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

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

    public Person() {
    }

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

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

Buffer缓冲器：

底层就是一个数组，主要用于和Channel通道配合，完成数据的传输

Buffer是一个抽象类，抽象类不能直接new对象，需要使用其子类

ByteBuffer

ShortBuffer

IntBuffer

LongBuffer

FloatBuffer

DoubleBuffer

CharBuffer

注意：子类不能使用new对象，需要通过allocate方法去创建

capacity : 容量

limit    : 可以操作到哪个索引（界限）

position : 当前准备操作的索引

mark	 : 标记，用来记录当前position的值

reset	 : 如果position的值发生了变化，那么通道随reset可以反馈记录的那个值

import java.nio.ByteBuffer;
public class ExDemo {
    public static void main(String[] args) {
        //创建一个容器
        ByteBuffer buffer = ByteBuffer.allocate(1024);
        System.out.println("缓冲器的容量："+buffer.capacity());
        System.out.println("界限："+ buffer.limit());
        System.out.println("索引："+ buffer.position());
        System.out.println("----------------------------------");

        //向容器中存数据
        buffer.put("abcde".getBytes());
        System.out.println("缓冲器的容量："+buffer.capacity());
        System.out.println("界限："+ buffer.limit());
        System.out.println("索引："+ buffer.position());
        System.out.println("----------------------------------");
        
        //切换读写模式
        buffer.flip();
        System.out.println("缓冲器的容量："+buffer.capacity());
        System.out.println("界限："+ buffer.limit());
        System.out.println("索引："+ buffer.position());
        System.out.println("----------------------------------");

        //读数据
        byte[] bytes = new byte[buffer.limit()];
        buffer.get(bytes);
        System.out.println(new String(bytes));
        System.out.println("缓冲器的容量："+buffer.capacity());
        System.out.println("界限："+ buffer.limit());
        System.out.println("索引："+ buffer.position());
        System.out.println("----------------------------------");
    }
}

方式1：

import java.io.*;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;

public class ExDemo {
    public static void main(String[] args) throws IOException {
        // 1.创建输入输出流对象
        FileInputStream fis = new FileInputStream("E:\a.flv");
        FileOutputStream fos =  new FileOutputStream("D:\b.flv");

        // 2.获取输入和输出的通道
        FileChannel inChannel = fis.getChannel();
        FileChannel outChannel =  fos.getChannel();

        // 3.创建缓冲器
        ByteBuffer buffer = ByteBuffer.allocate(1024);

        while ((inChannel.read(buffer)) != -1){
            //切换读写模式
            buffer.flip();
            outChannel.write(buffer);
            buffer.clear();
        }

        inChannel.close();
        outChannel.close();
        fis.close();
        fos.close();
    }
}

方式2：

import java.io.*;
import java.nio.channels.FileChannel;

public class ExDemo {
    public static void main(String[] args) throws IOException {
        RandomAccessFile infile =  new RandomAccessFile("D:\a.flv","rw");
        RandomAccessFile outfile =  new RandomAccessFile("E:\a.flv","rw");

        // 1.获取通道
        FileChannel inChannel = infile.getChannel();
        FileChannel outChannel =  outfile.getChannel();

        long num = inChannel.transferTo(0,inChannel.size(),outChannel);

        if (num > 0){
            System.out.println("复制成功！");
        }

        infile.close();
        outfile.close();
        inChannel.close();
        outChannel.close();
    }
}

import java.io.*;
import java.nio.file.Path;
import java.nio.file.Paths;

public class ExDemo {
    public static void main(String[] args) throws IOException {
        // 1.获取Path对象
        Path path = Paths.get("D:\abc\a.fle");
        // 2.获取Path对象中的信息
        System.out.println(path.getRoot());         //获取根路径
        System.out.println(path.getParent());       //获取父路径
        System.out.println(path.getNameCount());    //path中的路径名称数

        for (int i = 0; i  获取路径名称
            Path name = path.getName(i);
            System.out.println(name);
        }

        System.out.println(path.toAbsolutePath());  //绝对路径
        System.out.println(path.toUri());           //网络资源定位符
    }
}

import java.io.*;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;
import java.util.ArrayList;
import java.util.List;

public class ExDemo {
    public static void main(String[] args) throws IOException {
        Path path = Paths.get("E:\abc\test");
        // 1.createDirectories:创建多级文件夹
        Files.createDirectories(path);

        // 2.createFile：创建文件
        Path filePath =  Paths.get("E:\abc\test\aaa.txt");
        Files.createFile(filePath);

        // 3.write：将文本行写入文件，并传入指定的写入模式
        ArrayList list = new ArrayList<>();
        list.add("这是第一行文本1");
        list.add("这是第一行文本2");
        list.add("这是第一行文本3");
        Files.write(filePath,list, StandardOpenOption.APPEND);

        // 4.readAllLines：从文件中读取所有的行
        List list1 = Files.readAllLines(filePath);
        System.out.println(list1);

        // 5.sizi：返回文件的大小，以字节为单位
        long size  = Files.size(filePath);
        System.out.println(size);

    }
}