Java I/O

如果当初陪着你的人走远了，那些日子回忆起来会模糊吗？

Java I/O

mark 标记
reset 重置
exist 存在
modified 变更
skip 跳过
flush 冲刷

File类

package z1;

import java.io.File;

public class FileTest {

    public static void main(String[] args) throws Exception {
        
        File file =new File("d:/","abc.txt");
        
        if(file.exists()) { //如果文件存在
            
            file.delete();  
        }
        else {
            file.createNewFile();
            System.out.println("文件已创建");
            System.out.println("文件信息：");
            System.out.println("名字："+file.getName());
            System.out.println("长度："+file.length());
            System.out.println("是否被隐藏："+file.isHidden());
            System.out.println("是否可读："+file.canRead());
            System.out.println("是否可写："+file.canWrite());
            System.out.println("绝对路径："+file.getAbsolutePath());
            System.out.println("父类路径："+file.getParent());
            System.out.println("最后修改时间："+file.lastModified());
        }
    }
}

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FileInputStream/FileOutputStream

package z2;

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

public class FileIoStream {

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

        File file=new File("d:/","love.txt");
        
        //写入
        FileOutputStream out=new FileOutputStream(file);
        byte byin[]="人生若只如初见".getBytes();
        out.write(byin);
        out.close();
        //getBytes() 是Java编程语言中将一个字符串转化为一个字节数组byte[]的方法。
        //String的getBytes()方法是得到一个系统默认的编码格式的字节数组。
            
    
        //读取
        FileInputStream in=new FileInputStream(file);
        byte byin2[]=new byte[1024];
        int len=in.read(byin);//获取长度
        System.out.println(new String(byin,0,len));//取byin字节数组0-len的字节
    
    }
}

FileWriter/FileReader

package z2;

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


public class FileWriterReader {

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

        File file=new File("d:/","love.txt");
        
        //写入
        FileWriter out=new FileWriter(file);
        out.write("111");
        out.close();

        //读取
        FileReader in=new FileReader(file);
        char byin[]=new char[1024];
        int len=in.read(byin);//获取长度
        System.out.println(new String(byin,0,len));//取byin字节数组0-len的字节
    }
}

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BufferedWriter/BufferedReader

package z3;

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

public class BufferedIO {
    

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

        String content[]= {"我好想你","最近怎么样","常联系"};
        File file=new File("d:/","BufferedWriteReader.txt");
        
        FileWriter fw=new FileWriter(file);
        BufferedWriter bw=new BufferedWriter(fw);
        for(int i=0;i<content.length;i++) {
            bw.write(content[i]);
            bw.newLine();
        }
        bw.close();
        fw.close();
            
        FileReader fr=new FileReader(file);
        BufferedReader br=new BufferedReader(fr);
        String s=null;
        int i=0;
        while((s=br.readLine())!=null) {
            i++;
            System.out.println("第"+i+"行："+s);
        }
        fr.close();
        br.close(); 
    }
}

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DataOutputStream/DataInputStream

package z4;

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.FileInputStream;
import java.io.FileOutputStream;

public class DataIOStream {

    public static void main(String[] args) throws Exception {
        
        FileOutputStream fs = new FileOutputStream("word.txt");
        DataOutputStream ds = new DataOutputStream(fs);
        ds.writeUTF("使用writeUFT()方法写入数据;");
        ds.writeChars("使用writeChars()方法写入数据;");
        ds.writeBytes("使用writeBytes()方法写入数据.");![![iostream2.png](https://img.haomeiwen.com/i4448212/6d16ff4ad9f3063d.png?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240)
](https://img.haomeiwen.com/i4448212/edf8183217526309.png?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240)

        ds.close(); 
    
        FileInputStream fis = new FileInputStream("word.txt");
        DataInputStream dis = new DataInputStream(fis);
        System.out.println(dis.readUTF()); 
        
    }

                
}

image.png

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总结：

IO知识结构

image.png

File类

File file=new File("d:/","love.txt");
file.createNewFile();

file.delete();
file.exists();//是否存在
file.getName();
file.length();
file.isHidden();
file.canRead();
file.canWrite();
file.getAbsolutePath();
file.getParent();
file.lastModified();//最后修改时间

InputStream(字节输入父类)

read();
read(byte[] b);//读取字节，以整形返回字节数

mark(int readlimit);//在输入流当前位置放置一个标记，
//readlimit为在此标记失效前允许读取的字节数

reset();//将输入指针返回到当前所作标记处
skip(long n);/跳过输入流中的n个字节
markSupported();//如果当前流支持mark()/reset()方法返回true
close();

OutputStream(字节输出父类)

write(int b);
write(byte[] b);
write(byte[] b , int off , int len);

flush();//彻底完成输出并清空缓存区
close();

BufferedWriter/BufferedReader

read();
readLine();//读取一个文本行，返回字符串

write(String s , int off , int len);
newLine();//写入一个行分隔符

flush();//刷新该流缓存
close();

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参考资料：

• Java从入门到精通