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java基础 之 TXT文件处理(感觉比c++好用一些)

一:c/c++ 处理文件的用法,详见博客 c++文件操作

二:java与c++的方便之处:

(1) java在读取文件时,可以对字符流进行处理,重新进行编码,如 InputStreamReader reader = new InputStreamReader(new FileInputStream(file),encoding);

 (2) BufferReader bufferReader = new BufferReader(file) 进行buffer处理

(3)java的非常好用的一点就是,伸手就来,如 int 转 string  ( 如Integer.toString(intNumber) ),字符串分隔(stringStr.split(exp); ) ,字符串重新合成,直接加即可,非常好用;

(4)再借助于集成开发环境 IDE 缺少的依赖类,自动引入功能,更是如虎添翼。

三:处理TXT问文件的示例

package edu.tju.cs;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileWriter;
import java.io.InputStreamReader;

public class OriginalDevideByTime {
	
	String times[] = {"6:00:00","6:30:00","7:00:00","7:30:00","8:00:00","8:30:00","9:00:00","9:30:00","10:00:00","10:30:00",
			"11:00:00","11:30:00","12:00:00","12:30:00","13:00:00","13:30:00","14:00:00","14:30:00","15:00:00","15:30:00",
			"16:00:00","16:30:00","17:00:00","17:30:00","18:00:00","18:30:00","19:00:00","19:30:00","20:00:00","20:30:00",
			"21:00:00","21:30:00","22:00:00","22:30:00","23:00:00","23:30:00","24:00:00"};
	
	// 合成输出文件名
	public String getFileName(int cp){
		String fileName = "D:\\tjdata_metro\\results\\";
		fileName = fileName + Integer.toString(cp) + ".csv";
		return fileName;
	}
	// 读取文件,并分隔数据
	public void readTxtFile(String filePath){
		try {
	            String encoding="GBK";
	            File file=new File(filePath);
	            int cp = 1;
	            if(file.isFile() && file.exists()){ //判断文件是否存在
	                InputStreamReader read = new InputStreamReader(
	                new FileInputStream(file),encoding);//考虑到编码格式
	                BufferedReader bufferedReader = new BufferedReader(read);
	                
	                String originalLine = null;
	                String newLine = null;
	                
	                while((originalLine = bufferedReader.readLine()) != null){
	                	bufferedReader.mark((int)file.length()+1);// 设置文件标志位
	                
		                //写入文件名处理
	                	if(cp >= times.length)
	                		return;
		                String fileName = getFileName(cp);
	                	BufferedWriter writer = new BufferedWriter(new FileWriter(new File(fileName)));
	                	
		                while((originalLine = bufferedReader.readLine()) != null){
		                	// 字符串分隔
		                	String tmp[] = originalLine.split(",");
		                	// 如果符合重新合成
		                	if(tmp.length>3)
		                		if(tmp[3].compareTo(times[cp-1])>=0&&tmp[3].compareTo(times[cp])<0){
			                		newLine = tmp[0] + "," + tmp[1] + "," + tmp[2] + "," + tmp[3] + "," + tmp[4] + "," + tmp[5] + "," + tmp[6] + "," + tmp[7];
			                		System.out.println(newLine);
			                		writer.write(newLine + "\n");
			                	}
			                	else
			                		System.out.println("Not between times");
		                }
		                // 关闭写文件
		                writer.close();
		                // 重置为文件开始位置,cp自加
		                bufferedReader.reset();
		                cp ++;
	                }
	                bufferedReader.close();
	                read.close();
			    }
	            else
	            {
			        System.out.println("OriginalDevideByTime……找不到指定的文件");
			    }
	            
		    } catch (Exception e) {
		        System.out.println("OriginalDevideByTime……读取文件内容出错");
		        e.printStackTrace();
		    	}
			System.out.println("OriginalDevideByTime……Devide is over!!!");
	}
	
	// main 函数入口
	 public static void main(String argv[]){
	        String filePath = "D:\\tjdata_metro\\TOKEN_ENEX_201404_20W.csv";
	        OriginalDevideByTime devide = new OriginalDevideByTime();
	        
	        devide.readTxtFile(filePath);
	    }
	
}

四:学习心得:

(1)JAVA中文件指针复位到文件开头

File file = new File("temp.txt");  
BufferedReader  reader = null;  
reader = new BufferedReader(new FileReader(file));  
reader.mark((int)file.length()+1);  

// to do something

reader.reset();  
注意:如果文件串的最后一个字符是中文,使用mark()中的长度设为file.length()
如果文件的最后一个字符串是英文或数字,则java.io.IOException: Mark invalid,使用mark()中的长度设为file.length()+1  

mark用于标记当前位置;在读取一定数量的数据(小于readlimit的数据)后使用reset可以回到mark标记的位置;FileInputStream不支持mark/reset操作;BufferedInputStream支持此操作;
mark(readlimit)的含义是在当前位置作一个标记,制定可以重新读取的最大字节数,也就是说你如果标记后读取的字节数大于readlimit,你就再也回不到回来的位置了;通常InputStream的read()返回-1后,说明到达文件尾,不能再读取。除非使用了mark/reset

(2)JAVA中int转String类型有三种方法
1》String.valueOf(i)
2》 Integer.toString(i)
3》 i+""
valueOf()和toString()方法可以明白,但为什么3中加上一个""引号也可以?谁有资料可以看到?

(3)stringStr.compareTo(otherstring) ,相等返回 0 ,若是stringStr大于otherstring返回正数,若是stringStr小于otherstring返回负数

java基础 之 TXT文件处理(感觉比c++好用一些)