java IO流总结

首先我们把java中的io流分为三类：字符流、字节流、转换流

字符流

以字符的形式对文件进行处理，我们写一段复制文件的代码，主要用到两个类FileReader（读文件到内存），FileWriter（将内存中的数据写到文件）

public class Main  {
	 
    public static void main(String args[]) throws IOException{
    	//字符流
    	File file1 =new File("d:\\yll.txt");
    	File file2 = new File("d:\\copy.txt");
    	FileReader fr = new FileReader(file1);
    	FileWriter fw=new FileWriter(file2);
    	int len=-1;
    	char[] ch = new char[10];
    	while((len=fr.read(ch))!=-1){
    		fw.write(ch,0,len); ;
    	}
    	fr.close();
    	fw.close();
    }
}

除此之外，字符流还提供了两个缓冲区，用于提高上面代码的速度，分别是BufferedReader和BufferedWriter，我们用这两个类来实现上面的功能。

public class Main  {
	 
    public static void main(String args[]) throws IOException{
    	//字符流
    	File file1 =new File("d:\\yll.txt");
    	File file2 = new File("d:\\copy.txt");
    	FileReader fr = new FileReader(file1);
    	FileWriter fw=new FileWriter(file2);
    	int len=-1;
    	char[] ch = new char[10];
    	
    	BufferedReader br = new BufferedReader(fr);
    	BufferedWriter bw = new BufferedWriter(fw);
    	while((len=br.read(ch))!=-1){
    		bw.write(ch,0,len);
    	}
    	br.close();
    	bw.close();
    	
    }
}

字节流

顾名思义，以字节的形式对文件进行读写，跟上面一样，一共提供了四个类：FileInputStream，FileOutputStream、BufferedInputStream、BufferedOutputStream。直接上代码吧

不用缓冲区实现：

public class Main  {
	 
    public static void main(String args[]) throws IOException{
    	//字符流
    	File file1 =new File("d:\\yll.txt");
    	File file2 = new File("d:\\copy.txt");
    	
    	//字节流
    	FileInputStream fis = new FileInputStream(file1);
    	FileOutputStream fos = new FileOutputStream(file2);
    	byte b[]=new byte[1024];
    	int len=-1;
    	while((len=fis.read(b))!=-1){
    		fos.write(b, 0, len);
    	}
    	fis.close();
    	fos.close();
    	
    	
    }
}

用缓冲区实现：

public class Main  {
	 
    public static void main(String args[]) throws IOException{
    	//字符流
    	File file1 =new File("d:\\yll.txt");
    	File file2 = new File("d:\\copy.txt");
    	
    	//字节流
    	FileInputStream fis = new FileInputStream(file1);
    	FileOutputStream fos = new FileOutputStream(file2);
    	byte b[]=new byte[1024];
    	int len=-1;
    	
    	BufferedInputStream bis = new BufferedInputStream(fis);
    	BufferedOutputStream bos = new BufferedOutputStream(fos);
    	while((len=bis.read(b))!=-1){
    		bos.write(b, 0, len);
    	}
    	bis.close();
    	bos.close();
    	
    }
}

转换流

转换流一般在涉及编码的时候使用。

public class Main  {
	 
    public static void main(String args[]) throws IOException{
    	//字符流
    	File file1 =new File("d:\\yll.txt");
    	File file2 = new File("d:\\copy.txt");
    	
    	//转换流
    	InputStreamReader isr = new InputStreamReader(new FileInputStream(file1),"UTF-8");
    	OutputStreamWriter osw = new OutputStreamWriter(new FileOutputStream(file2),"GBK");
    	char ch[] = new char[1024];
    	int len=-1;
    	while((len=isr.read(ch))!=-1){
    		osw.write(ch, 0, len);
    	}
    	isr.close();
    	osw.close();
    }
}