day18 IO 字节流和字符流&正常关闭 转换流 Scanner Files

时间：2021-02-05 20:31:53

java.io.File类：表示了文件和目录

Windows和Unix中路径使用和路径分割 \和/     java中\表示转义，所以需要\\    分隔符; :

java中使用常量来表示可以解决此问题 separator   separatorChar  和   pathSeparator  pathSeparatorChar      :    /

File构造方法 

package file;

import java.io.File;

public class Demo1 {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		File f1 = new File("/User/luffy/123.txt");
		File f2 = new File("/User/luffy","123.txt");
		File f3 = new File("/User/luffy");
		new File(f3,"123.txt");
		
	}

}

常用方式

package _01_File;

import java.io.File;
import java.io.IOException;

public class Demo1 {
	public static void main(String[] args) throws Exception {
		File file = new File("test");
		System.out.println(file.exists());
		System.out.println(file.isDirectory());
		System.out.println(file.isFile());
		new File("test2.txt").createNewFile();
		new File("test/test2/test3").mkdirs();
		System.out.println(file.getName());
		//获取文件的相对路径
		System.out.println(file.getPath());
		//获取父目录  getParentFile()则返回的是File类型
		System.out.println(file.getParent());
		//获取绝对路径
		System.out.println(file.getAbsolutePath());
		//修改文件名称
		file.renameTo(new File("xxoo"));
		new File("delete.txt").delete();
		
	}

}
listFiles() 

package _01_File;

import java.io.File;

public class ListFilesDemo {
	public static void main(String[] args) {
		File file = new File("D:/图");
		listfiles(file);
		
	}
	static void listfiles(File file){
		if(file.isFile()){
			System.out.println(file);
		}
		if(file.isDirectory()){
			File[] fs = file.listFiles();
			if(null == fs){
				return;
			}
			for (File file2 : fs) {
				//System.out.println(file2);
				listfiles(file2);
			}
		}
	}

}

IO

表示输入/输出
java中的流分几种

1,从流向上考虑:输入/输出流

2,从流的单位上考虑:字节流,字符流

3,从流的功能上将:节点流/缓冲流

流的四大基类(抽象类)

day18 IO 字节流和字符流&正常关闭 转换流 Scanner Files

文件输出流

package _02_IO;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;

public class FileOutputStreamDemo {
	public static void main(String[] args) throws Exception {
		File file = new File("out.txt");
		FileOutputStream fos = new FileOutputStream(file);
		String data = "hello io";
		fos.write(data.getBytes());
		
		
		fos.close();
	}

}

文件输入流 

package _02_IO;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;

public class FileInputStreamDemo {
	public static void main(String[] args) throws Exception {
		File file = new File("out.txt");
		FileInputStream fis = new FileInputStream(file);
		
		//读取一个数据字节
		//int f1 = fis.read();
		//System.out.println(f1);
		
		
		//读取全部
		byte[] buffer = new byte[1024];
		int len = -1;
		while((len=fis.read(buffer)) != -1){
			System.out.println(len);
			System.out.println(new String(buffer,0,len));
		}
		fis.close();
	}

}
使用字节流拷贝文件 

package _02_IO;

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

public class CopyFile {

	/**
	 * @param args
	 * @throws Exception 
	 */
	public static void main(String[] args) throws Exception {
		File in =new File("out.txt");
		FileInputStream fis = new FileInputStream(in);
		FileOutputStream fos =new FileOutputStream("in.txt");
		byte[] buffer = new byte[2];
		int len=-1;
		while((len=fis.read(buffer)) != -1){
			fos.write(buffer,0,len);
		}
		fos.close();
		fis.close();
	}

}
字符异常的处理

1.7以前

package _02_IO;

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

public class CopyFileTry_Catch {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		FileInputStream fis = null;
		FileOutputStream fos = null;
		try{
			fis = new FileInputStream("out.txt");
			fos = new FileOutputStream("in.txt");
			byte[] buffer = new byte[2];
			int len=-1;
			while((len=fis.read(buffer)) != -1){
				fos.write(buffer, 0, len);
			}
		}catch(Exception e){
			e.printStackTrace();
		}finally{
			try {
				fos.close();
			} catch (IOException e) {
				e.printStackTrace();
			}finally{
				try {
					fis.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		}
		
		
		
		
	}

}
1.7后 

package _02_IO;

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

public class CoptFile_Try_Catch_17 {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		try(
				FileInputStream fis = new FileInputStream("out.txt");
				FileOutputStream fos = new FileOutputStream("in.txt");
				
			){
				int len = -1;
				byte[] buffer = new byte[2];
				while((len=fis.read(buffer)) != -1){
					fos.write(buffer,0,len);
				}
			
		}catch(IOException e){
			e.printStackTrace();
		}
	}

}
Scanner 

package _03_scanner;

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;

public class Demo1 {
	public static void main(String[] args) {
		//demo1();
		Scanner sc = new Scanner(System.in);
		while(true){
			String name = sc.next();
			System.out.println("echo"+name);
		}
	}

	private static void demo1() throws FileNotFoundException {
		Scanner sc = new Scanner(new File("out.txt"));
		while(sc.hasNextLine()){
			System.out.println(sc.nextLine());
		}
	}

}
字符流

一般有中文使用,任何时候可以使用字节流,一般操作二进制文件,就只能使用字节流
FileWriter

FileReader

字节流的拷贝文件

package writerAndreader;

import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.Reader;
import java.io.Writer;

public class Demo1 {

	/**
	 * @param args
	 * @throws Exception 
	 */
	public static void main(String[] args) throws Exception {
		Reader reader = new FileReader("op.txt");
		Writer writer = new FileWriter("mon.txt");
		char[] buffer = new char[1024];
		int len = -1;
		while((len=reader.read(buffer)) != -1){
			writer.write(buffer, 0, len);
		}
		writer.close();
		reader.close();
	}

}
当只提供字节流时候可以通过InputStreamReader和OutputStreamWriter来进行转换 

package writerAndreader;

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

public class Demo2 {

	/**
	 * @param args
	 * @throws Exception 
	 */
	public static void main(String[] args) throws Exception {
		FileInputStream fis = new FileInputStream("op.txt");
		FileOutputStream fos = new FileOutputStream("qq.txt");
		//如果这里只有字节输入和输出 FileInputStream OutputStream
		//那么通过什么来转换呢
		Reader reader = new InputStreamReader(fis);
		Writer writer = new OutputStreamWriter(fos);
		//后面的就一样了
		int len = -1;
		char[] buffer = new char[1024];
		while((len=reader.read(buffer)) != -1){
			writer.write(buffer, 0, len);
		}
		writer.close();
		reader.close();
	}

}
Files工具类 

package writerAndreader;

import java.io.File;
import java.io.FileInputStream;
import java.io.InputStream;
import java.net.URI;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;

public class Demo3 {

	/**
	 * @param args
	 * @throws Exception 
	 */
	@SuppressWarnings("deprecation")
	public static void main(String[] args) throws Exception {
		InputStream in = new FileInputStream("op.txt");
		//这个是一种方法
		//Files.copy(in,Paths.get("xxoo.txt"));
		//这个是第二种方法
		URI uri = new File("tt.txt").toURI();
		Path path = Paths.get(uri);
		Files.copy(in,path);
	}

}






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