JAVA 读写文件

1，JAVA读写文件主要用到JAVA的IO里边的BufferedReader来读取，BufferedWriter来写文件。

import java.io.BufferedReader;

import java.io.BufferedWriter;

import java.io.File;

import java.io.FileInputStream;

import java.io.FileNotFoundException;

import java.io.FileWriter;

import java.io.IOException;

import java.io.InputStreamReader;



public class MBFileManager {



    

    

    private  static final String PATH="E:/test";

    

    

    //constructor

    

    public MBFileManager(){

        initFolder();

        

    }

    

    public File initFolder(){

        File folder=new File(PATH);

        //folder not exist create a new folder

        if(!folder.exists()){

            folder.mkdir();

        }

        return folder;    

        

    }

    

    public  File getFile() {

        File[] fileList=initFolder().listFiles();

        File   file2get = null;

        if(fileList.length>0){

            file2get=fileList[fileList.length-1];

        }

        else{

            file2get=new File(PATH+"/"+"test"+fileList.length+".txt");

            //create a file

            try {

                file2get.createNewFile();

            } catch (IOException e) {

                // TODO Auto-generated catch block

                e.printStackTrace();

            }

        }

        return file2get;

    }

    

    public void createAnewFile(){

        File[] fileList=initFolder().listFiles();

        File   file2create=new File(PATH+"/"+"test"+fileList.length+".json");

        try {

            file2create.createNewFile();

        } catch (IOException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        }

    }

    

    public void readFile(){

        BufferedReader bufReader = null;

        try {

            

            bufReader=new BufferedReader(new InputStreamReader(new FileInputStream(getFile())));

        } catch (FileNotFoundException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        }

        

        try {

            String temp=null;

            while((temp=bufReader.readLine())!=null){

                System.out.println(temp);

            }

            bufReader.close();

        } catch (IOException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        }

        

    }

    public void writeFile(String[] content){

        createAnewFile();

        File file2write = getFile();

        String content2write="{" +

                "\"MemberDB_Coordinate_IMEI\":\"@a@\"" +","+

                "\"MemberDB_Coordinate_Longitude\":\"@b@\"" +","+

                "\"MemberDB_Coordinate_Latitudes\":\"@c@\"" +","+

                "\"MemberDB_Coordinate_CurrentTime\":\"@d@\"" +","+

                "\"MemberDB_Coordinate_UploadTime\":\"@e@\"" +","+

                "\"Coordinate_VersionCode\":\"@f@\""+

                "}";

       //replaceFirst这个方法一定要像下面这样写，才能有效果，因为如果你6个下来都是这样的话，不赋值，就保存不了你已经替换的字符串。因为它只管操作不管保存。

        content2write=content2write.replaceFirst("@a@", content[0]);

        content2write=content2write.replaceFirst("@b@", content[1]);

        content2write=content2write.replaceFirst("@c@", content[2]);

        content2write=content2write.replaceFirst("@d@", content[3]);

        content2write=content2write.replaceFirst("@e@", content[4]);

        content2write=content2write.replaceFirst("@f@", content[5]);

　　　　　//下面这部分是当文件大小超过5KB的时候就新建一个文件

        /*try {

            if(file2write.length()>5000){

                createAnewFile();

                file2write=getFile();

            }

            raf=new RandomAccessFile (file2write,"rw");

            raf.seek(raf.length());

            raf.writeBytes("\n"+content);

            raf.close();

        } catch (IOException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        }*/

        try {

            BufferedWriter bufWriter=new BufferedWriter(new FileWriter(file2write));

            bufWriter.write(content2write);

            bufWriter.close();

        } catch (IOException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        }

        

        

        

    }

}

2.字符串的拆分

很多时候拆分字符串的时候我们都用string的subString。但是如果用split();这个方法会更加简单。

public static String[] getValues(String v){

String value=v;

String values[]=value.split(",");

return values;

}

输入一个字符（假如以字符串里面的  ，号为分割）串就会返回字符串数组。