Java IO流如何操作(创建，读取，删除，写入)文件呢?

创建一个新文件

import java.io.*;
class TestClass{
    public static void main(String[] args) {
        File f=new File("D:\\test.txt");
        try{
            f.createNewFile();
        }catch (Exception e) {
            e.printStackTrace();
        }
    }
}

删除一个文件

import java.io.*;
class TestClass{
    public static void main(String[] args) {
        String fileName="D:"+File.separator+"test.txt";
        File f=new File(fileName);
        if(f.exists()){
            f.delete();
        }else{
            System.out.println("文件不存在");
        }
         
    }
}

IO流创建一个文件夹

import java.io.*;
class TestClass{
    public static void main(String[] args) {
        String fileName="D:"+File.separator+"test";
        File f=new File(fileName);
        f.mkdir();
    }
}

列出指定目录的全部文件(包括隐藏文件)

import java.io.*;
class TestClass{
    public static void main(String[] args) {
        String fileName="D:"+File.separator;
        File f=new File(fileName);
        File[] str=f.listFiles();
        for (int i = 0; i < str.length; i++) {
            System.out.println(str[i]);
        }
    }
}

使用RandomAccessFile写入文件

import java.io.*;
class TestClass{
    public static void main(String[] args) throws IOException {
        String fileName="D:"+File.separator+"test.txt";
        File f=new File(fileName);
        RandomAccessFile demo=new RandomAccessFile(f,"rw");
        demo.writeBytes("asdsad");
        demo.writeInt(12);
        demo.writeBoolean(true);
        demo.writeChar('A');
        demo.writeFloat(1.21f);
        demo.writeDouble(12.123);
        demo.close();  
    }
}

向文件中写入字符串

import java.io.*;
class TestClass{
    public static void main(String[] args) throws IOException {
        String fileName="D:"+File.separator+"test.txt";
        File f=new File(fileName);
        OutputStream out =new FileOutputStream(f);
        String str="java265.com";
        byte[] b=str.getBytes();
        out.write(b);
        out.close();
    }
}

向文件中追加新内容

import java.io.*;
class TestClass{
    public static void main(String[] args) throws IOException {
        String fileName="D:"+File.separator+"test.txt";
        File f=new File(fileName);
        OutputStream out =new FileOutputStream(f,true);
        String str="Java265.com"; 
        byte[] b=str.getBytes();
        for (int i = 0; i < b.length; i++) {
            out.write(b[i]);
        }
        out.close();
    }
}

读取文件内容

import java.io.*;
class TestClass{
    public static void main(String[] args) throws IOException {
        String fileName="D:"+File.separator+"test.txt";
        File f=new File(fileName);
        InputStream in=new FileInputStream(f);
        byte[] b=new byte[1024];
        int count =0;
        int temp=0;
        while((temp=in.read())!=(-1)){
            b[count++]=(byte)temp;
        }
        in.close();
        System.out.println(new String(b));
    }
}