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。