韩顺平java零基础课件韩顺平java资料百度网盘

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mob64ca140651e5 2023-10-12 17:29:14

文章标签 韩顺平java零基础课件 java 开发语言后端处理流 文章分类 Java 后端开发

另附一张一小部分不完全的思维导图

IO流

1.原理以及分类

1.1分类

四个抽象类：

1.2 文件和流

2.文件字节流：FileInputStream

2.1 案例

2.2 关键代码

在此省略了异常之类的代码非完整代码只截取关键部分代码

单个字节读取：慢(单个）汉字乱码(字节）

FileInputSteam fis = new FileInputStream("filePath");
while(int readData = fis.read()!=-1){ sout((char) readData);}
finally{fis.close();}

字节数组读取：快一些但因不是字符读取仍有汉字乱码问题

byte[] buf = byte[8];
FileInputSteam fis = new FileInputStream("filePath");
while(readLen = fis.read(buf)!=-1){ sout(new String(buf,0,readLen));}
finally{fis.close();}

3. 文件字节流：FileOutputStream

3.1 案例

3.2 关键代码

FileOutputStream fos = new FileOutputStream(path);
String str = "hello word"
fos.write(str.getBytes());
fos.close();

4. 文件拷贝

4.1关键代码

String path = "D:/output",path1 = "D:/out";
FileInputStream fis = new FileInputStream(path);
FileOutputStream fos = new FileOutputStream(path1);
 //定义字节数组
            byte[] buf = new byte[1024];
            int readLen;//获得buf的真实长度
            while((readLen = fis.read(buf))!=-1){
                fos.write(buf,0,readLen);//一定要这么写
            }
//关闭
             if(fis!=null){
                fis.close();
            }
            if(fos!=null){
                fos.close();
            }

4.2完整代码

public class main {
    public static void main(String[] args) {
        String path = "D:/output",path1 = "D:/out";
        FileInputStream fis = null;
        FileOutputStream fos = null;

        try {
            fis = new FileInputStream(path);
            fos = new FileOutputStream(path1);
            //定义字节数组
            byte[] buf = new byte[1024];
            int readLen;
            while((readLen = fis.read(buf))!=-1){
                fos.write(buf,0,readLen);//一定要这么写
            }
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            try{
            if(fis!=null){
                fis.close();
            }
            if(fos!=null){
                fos.close();
            }
            }catch (IOException e){
                e.printStackTrace();
            }
        }
    }
}

5.文件字符流

5.1FileReader

5.1.1案例

5.1.2关键代码

String path = "";
FileReader fr = new FileReader(path);
//定义字符数组
		char[] cbuf = new char[9];
		int data;
		while((data=fr.read(cbuf)!=-1){
			sout(new String(cbuf,0,data));
		}
//关闭
		fr.close();

5.2FileWriter

5.2.1案例

5.2.2关键代码

String path = "";
FileWriter fw = new FileWriter(path);
	String str = "风雨之后 定见彩虹";
	fw.write(str);
//必须关闭或者flush() 不然写不进去
		fw.close();

6.节点流与处理流

基本概念：

节点流：
处理流：

6.1处理流设计模式

6.2 字符处理流：BufferedReader BufferedWriter

注意：不要用字符处理流来处理一些二进制之之类的字节文件：如视频、音频等

6.2.1案例

6.2.2关键代码

String path = "D:/output";
String path1 = "D:/output1";
BufferedWriter bwriter = new BufferedWriter(new FileWriter(path1));
BufferedReader breader = new BufferedReader(new FileReader(path));
        String line ;
        while((line = breader.readLine())!=null){
            bwriter.write(line);
            bwriter.newLine();//换行
        }
//关闭处理流即可（因为底层会关闭filewriter/filereader）
        bwriter.close();
        breader.close();
    }
}

6.2.3完整代码

package HomeWork0118.hw4;

import java.io.*;
public class main {
    public static void main(String[] args) throws IOException {
        String path = "D:/output";
        String path1 ="D:/output1";
        BufferedWriter bwriter = new BufferedWriter(new FileWriter(path1));
        BufferedReader breader = new BufferedReader(new FileReader(path));
        String line;
        while((line = breader.readLine())!=null){
            bwriter.write(line);
            bwriter.newLine();
        }
        breader.close();
        bwriter.close();
    }
}

6.3 字节处理流 :BufferedInputStream BufferedOutputStream

6.3.1案例

6.3.2关键代码

String path = "D:/output";
String path1 = "D:/output1";
BufferedOutputStream bos = new BufferedWriter(new FileOutputStream(path1));
BufferedInputStream bis = new BufferedReader(new FileInputStream(path));
//定义字节数组
		byte[] buf = new byte[1024];
		int readLen;
        while((readLen = bis.read(buf))!=-1){
            bos.write(buf,1,readLen);
        }
//关闭处理流即可（因为底层会关闭filewriter/filereader）
        bis.close();
        bos.close();
    }
}