IO流拷贝文件的几种方式-阿里云开发者社区

通过IO流拷贝文件的几种方式如下:

需求1: 拷贝纯文本文件.

FileInputStream && FileOutputStream

普通的字节流一次读写一个字节.

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

public class Demo1 {
    public static void main(String[] args) throws Exception {
        //创建字节输入流对象,关联数据源文件
        FileInputStream fileInputStream = new FileInputStream("src\\input.txt");//不写绝对地址则默认项目目录下的地址
        //创建字节输出流对象,关联目的地文件 
        //补充:new FileOutputStream("input.txt",true),从文本末尾开始写入数据,不会覆盖原本内容,不写true则默认为false,会从文本头开始写入,覆盖原本内容
        FileOutputStream fileOutputStream = new FileOutputStream("src\\output.txt");//不写绝对地址则默认项目目录下的地址
        int len;//用于接收读取的字符
        //fileInputStream.read返回类型为int型,如果没有数据则返回-1
        //循环读取, 只要条件满足, 就一直读, 并将读取到的数据赋值给变量.
        while ((len = fileInputStream.read()) != -1) {
            // 将读取到的数据写入到目的地文件中.
            fileOutputStream.write(len);
        }
        //关流,释放资源
        fileInputStream.close();
        fileOutputStream.close();
    }
}

普通的字节流一次读写一个字节数组. //掌握

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

public class Demo2 {
    public static void main(String[] args) throws Exception {
        //创建字节输入流对象,关联数据源文件
        FileInputStream fileInputStream = new FileInputStream("src\\input.txt");//不写绝对地址则默认项目目录下的地址
        //创建字节输出流对象,关联目的地文件
        FileOutputStream fileOutputStream = new FileOutputStream("src\\output.txt");//不写绝对地址则默认项目目录下的地址
        byte[] bytes = new byte[8192];
        int len;
        while ((len = fileInputStream.read(bytes)) != -1) {
            fileOutputStream.write(bytes, 0, len);
        }
        fileInputStream.close();
        fileOutputStream.close();
    }
}

BufferedInputStream && BufferedOutputStream

高效的字节流一次读写一个字节. //掌握

public class Demo3 {
    public static void main(String[] args) throws Exception{
        //创建输入流, 关联数据源文件
        BufferedInputStream bufferedInputStream = new BufferedInputStream(new FileInputStream("src\\input.txt"));//BufferedInputStream(InputStream )
        //创建输出流, 关联目的地文件
        //补充:new FileOutputStream("input.txt",true),从文本末尾开始写入数据,不会覆盖原本内容,不写true则默认为false,会从文本头开始写入,覆盖原本内容
        BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(new FileOutputStream("src\\output.txt"));//BufferedOutputStream(OutputStream)
        //定义变量, 用来记录读取到的数据(字节).
        int len;
        //循环读取, 只要条件满足, 就一直读, 并将读取到的数据赋值给变量.
        while((len = bufferedInputStream.read())!=-1){
        //将读取到的数据写入到目的地文件中.
            bufferedOutputStream.write(len);
        }
        //关闭流,释放资源
        bufferedInputStream.close();
        bufferedOutputStream.close();
    }

高效的字节流一次读写一个字节数组.

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.FileInputStream;
import java.io.FileOutputStream;

public class Demo4 {
    public static void main(String[] args) throws Exception {
        //创建输入流, 关联数据源文件
        BufferedInputStream bufferedInputStream = new BufferedInputStream(new FileInputStream("src\\input.txt"));//BufferedInputStream(InputStream )
        //创建输出流, 关联目的地文件.
        BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(new FileOutputStream("src\\output.txt"));//BufferedOutputStream(OutputStream)
        //接收数据
        byte[] bytes = new byte[8192];//建议数组长度设置为8192,与字节缓冲区长度相同.
        //定义变量, 用来记录读取到的数据(字节).
        int len;
        //循环读取, 只要条件满足, 就一直读, 并将读取到的数据赋值给变量.
        while ((len = bufferedInputStream.read(bytes)) != -1) {
            //将读取到的数据写入到目的地文件中.
            bufferedOutputStream.write(bytes, 0, len);
        }
        //关流,释放资源
        bufferedInputStream.close();
        bufferedOutputStream.close();
    }
}

InputStreamReader && OutputStreamWriter

转换流一次读写一个字符.

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;

public class Demo5 {
    public static void main(String[] args) throws Exception {
        InputStreamReader inputStreamReader = new InputStreamReader(new FileInputStream("src\\input.txt"));
        OutputStreamWriter outputStreamWriter = new OutputStreamWriter(new FileOutputStream("src\\output.txt"));
        int len;
        while ((len = inputStreamReader.read())!=-1){
            outputStreamWriter.write(len);
        }
        inputStreamReader.close();
        outputStreamWriter.close();
    }
}

转换流一次读写一个字符数组.

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;

public class Demo6 {
    public static void main(String[] args) throws Exception {
//new InputStreamReader(new FileInputStream("day12/data/1.txt"),"utf-8");设置读取格式为utf-8,如果不设置格式,则为当前编译器默认的编码
        InputStreamReader inputStreamReader = new InputStreamReader(new FileInputStream("src\\input.txt"));
//new OutputStreamWriter(new FileOutputStream("day12/data/2.txt"),"utf-8");设置读取格式为utf-8,如果不设置格式,则为当前编译器默认的编码
        OutputStreamWriter outputStreamWriter = new OutputStreamWriter(new FileOutputStream("src\\output.txt"));
        int len;
        char[] bytes = new char[8192];
        while ((len = inputStreamReader.read(bytes)) != -1) {
            outputStreamWriter.write(bytes, 0, len);
        }
        inputStreamReader.close();
        outputStreamWriter.close();
    }
}

FileReader && FileWriter

普通的字符流一次读写一个字符.

import java.io.FileReader;
import java.io.FileWriter;

public class Demo7 {
   public static void main(String[] args) throws Exception {
       FileReader fileReader = new FileReader("src\\input.txt");
       FileWriter fileWriter = new FileWriter("src\\output.txt");
       int len;
       while ((len = fileReader.read()) != -1) {
           fileWriter.write(len);
       }
       fileReader.close();
       fileWriter.close();
   }
}

普通的字符流一次读写一个字符数组.

public class Demo8 {
    public static void main(String[] args) throws Exception {
        FileReader fileReader = new FileReader("src\\input.txt");
        FileWriter fileWriter = new FileWriter("src\\output.txt");
        int len;
        char[] chars = new char[8192];
        while ((len = fileReader.read(chars)) != -1) {
            fileWriter.write(chars, 0, len);
        }
        fileReader.close();
        fileWriter.close();
    }
}

BufferedReader && BufferedWriter

高效的字符流一次读写一个字符.

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

public class Demo9 {
    public static void main(String[] args)throws Exception {
        BufferedReader bufferedReader = new BufferedReader(new FileReader("src\\input.txt"));
        BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter("src\\output.txt"));
        int len;
        while ((len = bufferedReader.read())!=-1){
            bufferedWriter.write(len);
        }
        bufferedReader.close();
        bufferedWriter.close();
    }
}

高效的字符流一次读写一个字符数组.

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

public class Demo10 {
    public static void main(String[] args) throws Exception {
        BufferedReader bufferedReader = new BufferedReader(new FileReader("src\\input.txt"));
        BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter("src\\output.txt"));
        int len;
        char[] chars = new char[8192];
        while ((len = bufferedReader.read(chars)) != -1) {
            bufferedWriter.write(chars, 0, len);
        }
        bufferedReader.close();
        bufferedWriter.close();
    }
}

高效的字符流一次读写一行. //掌握

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

public class Demo11 {
    public static void main(String[] args) throws Exception {
        BufferedReader bufferedReader = new BufferedReader(new FileReader("src\\input.txt"));
        BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter("src\\output.txt"));
        String len;
        while ((len = bufferedReader.readLine()) != null) {
            bufferedWriter.write(len);
            bufferedWriter.newLine();//换行
        }
        bufferedReader.close();
        bufferedWriter.close();
    }
}

需求2: 拷贝任意类型的文件.

        1. 普通的字节流一次读写一个字节.
        2. 普通的字节流一次读写一个字节数组.
        3. 高效的字节流一次读写一个字节.
        4. 高效的字节流一次读写一个字节数组.

IO流拷贝文件的几种方式

需求1: 拷贝纯文本文件.

FileInputStream && FileOutputStream

BufferedInputStream && BufferedOutputStream

InputStreamReader && OutputStreamWriter

FileReader && FileWriter

BufferedReader && BufferedWriter

需求2: 拷贝任意类型的文件.

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