字符流和字节流copy速度对比

港控/mmm° 2022-05-25 01:07 113阅读 0赞

1.字符流对文件的copy

注意：字符流只能对文本文件进行操作，字符类最好用字符流去copy。

package com.yidongxueyuan.Iofile;
    
    import java.io.BufferedReader;
    import java.io.BufferedWriter;
    import java.io.FileReader;
    import java.io.FileWriter;
    import java.io.IOException;
    
    public class TextCopyDemo_01 {
    	public static void main(String[] args) throws IOException {
    		/**
    		 * 字符流方法
    		 * 1.单个字符copy
    		 * 2.字符数组copy
    		 * 3.高效单字符copy
    		 * 4.高效字符数组copy
    		 * 5.高效字符行copy
    		 */
    		copy_01();
    		copy_02();
    		copy_03();
    		copy_04();
    		copy_05();
    	}
    	private static void copy_01() throws IOException
    	{
    		FileReader fr = new FileReader("D:\\dn.txt");
    		FileWriter fw = new FileWriter("E:\\CopyFile\\copy_01.txt");
    		
    		int num = 0;
    		long start = System.currentTimeMillis();
    		while((num=fr.read())!=-1)
    		{
    			fw.write(num);
    			fw.flush();
    		}
    		long end = System.currentTimeMillis();
    		System.out.println("time_01: "+(end-start));
    		fr.close();
    		fw.close();
    	}
    	private static void copy_02() throws IOException
    	{
    		FileReader fr = new FileReader("D:\\dn.txt");
    		FileWriter fw = new FileWriter("E:\\CopyFile\\copy_02.txt");
    		int len = 0;
    		char ch[] = new char[1024];
    		long start = System.currentTimeMillis();
    		while((len=fr.read(ch))!=-1)//len是读取的字符数。如果已到达流的末尾，则返回 -1 。
    		{
    //			fw.write(ch,0,len);
    //			fw.write(len);
    //			fw.write(ch.toString(),0,len);//toString()方法没有被重写
    //			fw.write(new String(ch),0,len);
    			fw.write(new String(ch,0,len));//传递一个字符串对象！
    			fw.flush();
    		}
    		long end = System.currentTimeMillis();
    		System.out.println("time_02: "+(end-start));
    		fr.close();
    		fw.close();
    	}
    	private static void copy_03() throws IOException
    	{
    		BufferedReader bur = new BufferedReader(new FileReader("D:\\dn.txt"));
    		BufferedWriter buw = new BufferedWriter(new FileWriter("E:\\CopyFile\\copy_03.txt"));
    		
    		int num = 0;
    		long start = System.currentTimeMillis();
    		while((num=bur.read())!=-1)
    		{
    			buw.write(num);
    			buw.flush();
    		}
    		long end = System.currentTimeMillis();
    		System.out.println("time_03: "+(end-start));
    		
    		bur.close();
    		buw.close();
    	}
    	private static void copy_04() throws IOException
    	{
    		BufferedReader bur = new BufferedReader(new FileReader("D:\\dn.txt"));
    		BufferedWriter buw = new BufferedWriter(new FileWriter("E:\\CopyFile\\copy_04.txt"));
    		
    		int num = 0;
    		char ch[] = new char[1024];
    		long start = System.currentTimeMillis();
    		while((num=bur.read(ch,0,ch.length))!=-1)//num为读取的字符数，如果已到达流末尾，则返回 -1 
    		{
    //			buw.write(ch,0,num);
    			buw.write(new String(ch),0,num);
    			buw.flush();
    		}
    		long end = System.currentTimeMillis();
    		System.out.println("time_04: "+(end-start));
    		
    		bur.close();
    		buw.close();
    	}
    	private static void copy_05() throws IOException
    	{
    		BufferedReader bur = new BufferedReader(new FileReader("D:\\dn.txt"));
    		BufferedWriter buw = new BufferedWriter(new FileWriter("E:\\CopyFile\\copy_05.txt"));
    		
    		String str = null;
    		long start = System.currentTimeMillis();
    		while((str=bur.readLine())!=null)//str为包含该行内容的字符串，不包含任何行终止符，如果已到达流末尾，则返回 null(遇到换行就停)
    		{
    //			buw.write(ch,0,num);
    			buw.write(str);//写完一行，使用的是父类中的write(String str);方法
    			buw.newLine();
    			buw.flush();
    		}
    		long end = System.currentTimeMillis();
    		System.out.println("time_05: "+(end-start));
    		
    		bur.close();
    		buw.close();
    	}
    
    }

运行结果如下：

![20180505031456797][]

![2018050503150769][]

经检查，copy出来的文件与源文件属性相同。

由此可见，虽然都是对文件进行了copy，但是快慢却不相同， 单个字符copy>高效单字符copy>字符数组copy>高效字符行copy>高效字符数组copy。由此得出，字符流copy文本文件时，使用高效字符数组copy文本文件是较合适的选择。

2.字节流对文件的copy

package com.yidongxueyuan.Iofile;
    
    import java.io.BufferedInputStream;
    import java.io.BufferedOutputStream;
    import java.io.FileInputStream;
    import java.io.FileNotFoundException;
    import java.io.FileOutputStream;
    import java.io.IOException;
    
    public class StreamCopyDemo_01 {
    	public static void main(String[] args) throws IOException, InterruptedException {
    		/**
    		 * 字节流copy
    		 * 一、文本文档
    		 *   1.单个字节copy
    		 *   2.字节数组copy
    		 *   3.高效的单字节copy
    		 *   4.高效的字节数组copy
    		 * 二、图片
    		 *   1.单个字节copy
    		 *   2.字节数组copy
    		 *   3.高效的单字节copy
    		 *   4.高效的字节数组copy
    		 * 三、视频
    		 *   1.单个字节copy
    		 *   2.字节数组copy
    		 *   3.高效的单字节copy
    		 *   4.高效的字节数组copy
    		 */
    		txtcopy_01();
    		txtcopy_02();
    		txtcopy_03();
    		txtcopy_04();
    		photocopy_01();
    		photocopy_02();
    		photocopy_03();
    		photocopy_04();
    		videocopy_01();
    		videocopy_02();
    		videocopy_03();
    		videocopy_04();
    	}
    	//文本文档单个字节copy
    	private static void txtcopy_01() throws FileNotFoundException, IOException {
    		FileInputStream fis = new FileInputStream("D:\\dn.txt");
    		FileOutputStream fos = new FileOutputStream("E:\\CopyFile\\1copy_01.txt");
    		
    		int num = 0;
    		long start = System.currentTimeMillis();
    		while((num=fis.read())!=-1)//num为下一个数据字节；如果到达流的末尾，则返回 -1。
    		{
    			fos.write(num);
    		}
    		long end = System.currentTimeMillis();
    		System.out.println("txttime_01: "+(end-start));
    		fis.close();
    		fos.close();
    	}
    	//文本文档字节数组copy
    	private static void txtcopy_02() throws FileNotFoundException, IOException {
    		FileInputStream fis = new FileInputStream("D:\\dn.txt");
    		FileOutputStream fos = new FileOutputStream("E:\\CopyFile\\1copy_02.txt");
    		
    		int len = 0;
    		byte b[] = new byte[1024];
    		long start = System.currentTimeMillis();
    		while((len=fis.read(b))!=-1)//len为读入缓冲区的总字节数；如果因为已经到达流末尾而不再有数据可用，则返回 -1。
    		{
    //			fos.write(b);
    			fos.write(b, 0, len);//将指定 byte 数组中从偏移量 off 开始的 len 个字节写入此输出流。
    		}
    		long end = System.currentTimeMillis();
    		System.out.println("txttime_02: "+(end-start));
    		fis.close();
    		fos.close();
    	}
    	//文本文档高效的单字节copy
    	private static void txtcopy_03() throws IOException
    	{
    		BufferedInputStream bis = new BufferedInputStream(new FileInputStream("D:\\dn.txt"));
    		BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream("E:\\CopyFile\\1copy_03.txt"));
    		
    		int num = 0;
    		long start = System.currentTimeMillis();
    		while((num=bis.read())!=-1)//num为下一个数据字节；如果到达流的末尾，则返回 -1。
    		{
    			bos.write(num);
    		}
    		long end = System.currentTimeMillis();
    		System.out.println("txttime_03: "+(end-start));
    		
    		bis.close();
    		bos.close();
    	}
    	//文本文档高效的字节数组copy
    	private static void txtcopy_04() throws IOException
    	{
    		BufferedInputStream bis = new BufferedInputStream(new FileInputStream("D:\\dn.txt"));
    		BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream("E:\\CopyFile\\1copy_04.txt"));
    		
    		int len = 0;
    		byte b[] = new byte[1024];
    		long start = System.currentTimeMillis();
    		while((len=bis.read(b,0,b.length))!=-1)//num为下一个数据字节；如果到达流的末尾，则返回 -1。
    		{
    //			bos.write(num);
    			bos.write(b,0,len);//这里必须有范围，否则重复
    		}
    		long end = System.currentTimeMillis();
    		System.out.println("txttime_04: "+(end-start));
    		
    		bis.close();
    		bos.close();
    	}
    	//图片单个字节copy
    	private static void photocopy_01() throws FileNotFoundException, IOException {
    		FileInputStream fis = new FileInputStream("D:\\dn.jpg");
    		FileOutputStream fos = new FileOutputStream("E:\\CopyFile\\2copy_01.jpg");
    		
    		int num = 0;
    		long start = System.currentTimeMillis();
    		while((num=fis.read())!=-1)//num为下一个数据字节；如果到达流的末尾，则返回 -1。
    		{
    			fos.write(num);
    		}
    		long end = System.currentTimeMillis();
    		System.out.println("phototime_01: "+(end-start));
    		fis.close();
    		fos.close();
    	}
    	//图片字节数组copy
    	private static void photocopy_02() throws FileNotFoundException, IOException {
    		FileInputStream fis = new FileInputStream("D:\\dn.jpg");
    		FileOutputStream fos = new FileOutputStream("E:\\CopyFile\\2copy_02.jpg");
    		
    		int len = 0;
    		byte b[] = new byte[1024];
    		long start = System.currentTimeMillis();
    		while((len=fis.read(b))!=-1)//len为读入缓冲区的总字节数；如果因为已经到达流末尾而不再有数据可用，则返回 -1。
    		{
    //			fos.write(b);
    			fos.write(b, 0, len);//将指定 byte 数组中从偏移量 off 开始的 len 个字节写入此输出流。
    		}
    		long end = System.currentTimeMillis();
    		System.out.println("phototime_02: "+(end-start));
    		fis.close();
    		fos.close();
    	}
    	//图片高效的单字节copy
    	private static void photocopy_03() throws IOException
    	{
    		BufferedInputStream bis = new BufferedInputStream(new FileInputStream("D:\\dn.jpg"));
    		BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream("E:\\CopyFile\\2copy_03.jpg"));
    		
    		int num = 0;
    		long start = System.currentTimeMillis();
    		while((num=bis.read())!=-1)//num为下一个数据字节；如果到达流的末尾，则返回 -1。
    		{
    			bos.write(num);
    		}
    		long end = System.currentTimeMillis();
    		System.out.println("phototime_03: "+(end-start));
    		
    		bis.close();
    		bos.close();
    	}
    	//图片高效的字节数组copy
    	private static void photocopy_04() throws IOException
    	{
    		BufferedInputStream bis = new BufferedInputStream(new FileInputStream("D:\\dn.jpg"));
    		BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream("E:\\CopyFile\\2copy_04.jpg"));
    		
    		int len = 0;
    		byte b[] = new byte[1024];
    		long start = System.currentTimeMillis();
    		while((len=bis.read(b,0,b.length))!=-1)//num为下一个数据字节；如果到达流的末尾，则返回 -1。
    		{
    //			bos.write(num);
    			bos.write(b,0,len);//这里必须有范围，否则重复
    		}
    		long end = System.currentTimeMillis();
    		System.out.println("phototime_04: "+(end-start));
    		
    		bis.close();
    		bos.close();
    	}
    	//视频单个字节copy
    	private static void videocopy_01() throws FileNotFoundException, IOException {
    		FileInputStream fis = new FileInputStream("D:\\（二）PrintStream类.wmv");
    		FileOutputStream fos = new FileOutputStream("E:\\CopyFile\\3copy_01.wmv");
    		
    		int num = 0;
    		long start = System.currentTimeMillis();
    		while((num=fis.read())!=-1)//num为下一个数据字节；如果到达流的末尾，则返回 -1。
    		{
    			fos.write(num);
    		}
    		long end = System.currentTimeMillis();
    		System.out.println("videotime_01: "+(end-start));
    		fis.close();
    		fos.close();
    	}
    	//视频字节数组copy
    	private static void videocopy_02() throws FileNotFoundException, IOException {
    		FileInputStream fis = new FileInputStream("D:\\（二）PrintStream类.wmv");
    		FileOutputStream fos = new FileOutputStream("E:\\CopyFile\\3copy_02.wmv");
    		
    		int len = 0;
    		byte b[] = new byte[1024];
    		long start = System.currentTimeMillis();
    		while((len=fis.read(b))!=-1)//len为读入缓冲区的总字节数；如果因为已经到达流末尾而不再有数据可用，则返回 -1。
    		{
    //			fos.write(b);
    			fos.write(b, 0, len);//将指定 byte 数组中从偏移量 off 开始的 len 个字节写入此输出流。
    		}
    		long end = System.currentTimeMillis();
    		System.out.println("videotime_02: "+(end-start));
    		fis.close();
    		fos.close();
    	}
    	//视频高效的单字节copy
    	private static void videocopy_03() throws IOException
    	{
    		BufferedInputStream bis = new BufferedInputStream(new FileInputStream("D:\\（二）PrintStream类.wmv"));
    		BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream("E:\\CopyFile\\3copy_03.wmv"));
    		
    		int num = 0;
    		long start = System.currentTimeMillis();
    		while((num=bis.read())!=-1)//num为下一个数据字节；如果到达流的末尾，则返回 -1。
    		{
    			bos.write(num);
    		}
    		long end = System.currentTimeMillis();
    		System.out.println("videotime_03: "+(end-start));
    		
    		bis.close();
    		bos.close();
    	}
    	//视频高效的字节数组copy
    	private static void videocopy_04() throws IOException
    	{
    		BufferedInputStream bis = new BufferedInputStream(new FileInputStream("D:\\（二）PrintStream类.wmv"));
    		BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream("E:\\CopyFile\\3copy_04.wmv"));
    		
    		int len = 0;
    		byte b[] = new byte[1024];
    		long start = System.currentTimeMillis();
    		while((len=bis.read(b,0,b.length))!=-1)//num为下一个数据字节；如果到达流的末尾，则返回 -1。
    		{
    //			bos.write(num);
    			bos.write(b,0,len);//这里必须有范围，否则重复
    		}
    		long end = System.currentTimeMillis();
    		System.out.println("videotime_04: "+(end-start));
    		
    		bis.close();
    		bos.close();
    	}
    
    
    }

运行结果如下：

![20180505101955636][]

![2018050509484054][]

经检查，copy过来的文件属性值与源文件相同，copy成功。

分析得知： 单个字节copy>高效的单字节copy>字节数组copy>高效的字节数组copy。显然，高效字节数组copy方法是较合适的。

总结：copy文件时，如果是字符类，则可以在条件允许的情况下，使用高效字符数组copy。如果不是，则可以选择高效字节数组copy。

3.跟踪行号的缓冲字符输入流

read()读取单个字符。行结束符被压缩为一个换行（'\\n'）字符。无论何时读取行结束符，当前行号将加 1。

private static void copy_05() throws IOException,FileNotFoundException
    	{
    		//跟踪行号的缓冲字符输入流
    		LineNumberReader lnr = new LineNumberReader(new FileReader("D:\\dn.txt"));
    		BufferedWriter buw = new BufferedWriter(new FileWriter("E:\\CopyFile\\tcopy5.docx"));
    		
    		int num = 0;
    		long start1 = System.currentTimeMillis();
    		while((num=lnr.read())!=-1)//读到行结束符的时候行结束符被压缩为一个换行（'\n'）字符，因此在记事本中不能正常显示。
    		{
    			buw.write(num);
    			buw.flush();
    		}
    		long end1 = System.currentTimeMillis();
    		System.out.println("copytime5: "+(end1-start1));
    		lnr.close();
    		buw.close();
    		
    	}

copy之前文件里的数据：

![20180505104644791][]

copy之后文件里的数据：

![20180505104910235][]

可以看到，由于行分隔符被压缩为“\\n”,而记事本的行分隔符为“/r/n”，因此不能正常显示。

[20180505031456797]: /images/20220525/3e74abb0f6d84ce08c8ce8931f6c4df2.png
[2018050503150769]: /images/20220525/46f58b4fb0e64539a9d5672586325eb9.png
[20180505101955636]: /images/20220525/a993f349bd924440ba1f2f7f3f0e7353.png
[2018050509484054]: /images/20220525/27d2c769c5764a43bd3c3cdbb732ae95.png
[20180505104644791]: /images/20220525/721ca9db92d74d1bb87082c38a984503.png
[20180505104910235]: /images/20220525/235df1c05b4d4c47aacbead5502f6c39.png