java的read file 和write file

1.读文件

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;

public class Readfile {
    /*
  读取文件流
   */
    public BufferedReader bufferreader(String fileName) {
        BufferedReader reader = null; //使用缓冲区的方法将数据读入到缓冲区中
        try {
            reader = new BufferedReader(new InputStreamReader(new FileInputStream(fileName)));
        } catch (Exception e) {
            e.printStackTrace();
        }
        return reader;
    }
    /*
    读取文件中的某一行数据
     */
    public String readfile(BufferedReader reader, int lineNumber) {
        String line = null; //定义行数
        try {
            int num = 0;
            while (true) {
                num++;
                line = reader.readLine();
                if (num == lineNumber) {
                    break;
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (reader != null) {
                try {
                    reader.close();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
            return line;
        }

    }

    public static void main(String args[]){


        Readfile f=new Readfile();
        BufferedReader br= f.bufferreader("add2.txt");
        System.out.println(f.readfile(br,3));//获取某一行的数据


    }
}

　　2.写文件

 

import java.io.*;
import java.math.BigInteger;
import java.security.MessageDigest;
import java.text.DecimalFormat;
import java.time.LocalDate;
import java.time.format.DateTimeFormatter;
import java.util.*;
import java.util.concurrent.CountDownLatch;

public class Writefile2 {

    private static String[] id={"LB13","RR13","LR14","LR15","LR12",
           "LL13","LL14","LL12","LB14","LB12"};
    private static int tmp=0;
    private static FileWriter fw;
    private static FileWriter fw2;
    /*
    /*
获取需要生成的文件的大小
 */

    public BigInteger getsize(String size){
        //System.out.println(size.substring(0,size.length()-1));
        int x=Integer.valueOf(size.substring(0,size.length()-1));

        BigInteger resultlen=new BigInteger("0");
        if(size.endsWith("m")||size.endsWith("M")) {
            resultlen = BigInteger.valueOf(x).multiply(BigInteger.valueOf(1024)).multiply(BigInteger.valueOf(1024));
        }else if(size.endsWith("g")||size.endsWith("G")){
            resultlen = BigInteger.valueOf(x).multiply(BigInteger.valueOf(1024)).multiply(BigInteger.valueOf(1024)).multiply(BigInteger.valueOf(1024));
        }else if(size.endsWith("K")||size.endsWith("k")){
            resultlen = BigInteger.valueOf(x).multiply(BigInteger.valueOf(1024));
        }
        return resultlen;
    }

    public synchronized static int  getuuid()
    {
        tmp=tmp+1;

        return tmp;
    }
    /*
如果数据量不大的情况下，10G以下，可以使用该方法
file:文件名字
code:插入的内容
size是文件大小，可以是1G,1k,1m。如果想表示100B， 请用0.1K
 */
    public boolean writefile(int size) {
        DecimalFormat count=new DecimalFormat("00000000000");
        //经过测试：ufferedOutputStream执行耗时:1,1，1 毫秒
        int tmp_len=0;
        long begin0 = System.currentTimeMillis();
        try {
            StringBuffer data = new StringBuffer();
            String uuid=null;
            String uuid2=null;
            MessageDigest  md =MessageDigest.getInstance("MD5");
            LocalDate localdate=LocalDate.now();
            DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyyMMdd");
            String date=localdate.format(formatter);
            Random rd=new Random();
            int z=0;

            for(int i=0;i<size;i++){

                uuid=count.format(Integer.parseInt(String.valueOf(getuuid()))+1);
                md.update(uuid.getBytes());
                uuid2=(md.digest().toString()).substring(3);
                while(true) { //为了保证结果一定是有8位长度
                    if (uuid2.length()!= 8) {
                        uuid2 = (md.digest().toString()).substring(3);
                    }else{
                        break;
                    }
                }
                z= rd.nextInt(10);
                data.append("1|"); // 分区号
                data.append("B201912138999"); //批次号
                data.append("|C|1030844001362|");  //
                data.append(date+id[z]+uuid2+uuid);  //流水号
                data.append("|CNY|1.01|0110|00|C1030844001362|00|D1ANA102Y05ME003000062|1|1|1|1|1|1|CMB10|");  //
                data.append("2019-12-13-23.17.12.63504");//
                data.append("|1|ANA200X05ME007000E67|ANAVCK00|");//
                data.append(date);
                data.append("|231712|1|A|1|1|");
                data.append("\r\n");
                fw.write(data.toString());
                data.delete(0, data.length());
                }
                return true;
        } catch (Exception e1) {
            e1.printStackTrace();
            return false;
        } finally{
            long end0 = System.currentTimeMillis();
            System.out.println("BufferedOutputStream执行耗时:" + (end0 - begin0) + " 毫秒");
        }
    }

    public boolean writefile2(int size) {
        DecimalFormat count=new DecimalFormat("00000000000");
        //经过测试：ufferedOutputStream执行耗时:1,1，1 毫秒
        int tmp_len=0;
        long begin0 = System.currentTimeMillis();
        try {
            StringBuffer data2 = new StringBuffer();
            String uuid=null;
            String uuid2=null;
            MessageDigest  md =MessageDigest.getInstance("MD5");
            LocalDate localdate=LocalDate.now();
            DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyyMMdd");
            String date=localdate.format(formatter);
            Random rd=new Random();
            int z=0;

            for(int i=0;i<size;i++){

                uuid=count.format(Integer.parseInt(String.valueOf(getuuid()))+1);
                md.update(uuid.getBytes());
                uuid2=(md.digest().toString()).substring(3);
                while(true) { //为了保证结果一定是有8位长度
                    if (uuid2.length()!= 8) {
                        uuid2 = (md.digest().toString()).substring(3);
                    }else{
                        break;
                    }
                }
                z= rd.nextInt(10);
                data2.append("1|"); // 分区号
                data2.append("B201912138999"); //批次号
                data2.append("|C1030844001362|");
                data2.append(date+id[z]+uuid2+uuid);  //流水号
                //data2.append(date+"LR13"+uuid2+uuid);  //流水号
                data2.append("|CNY|0.12|0125|00|Q1030844001574|06|1|102100099996|C1030844001362|00|1|308584000013|1|");  //
                data2.append("2019-12-13-23.17.12.63504");//
                data2.append("|1|ANA200X05ME007000EUK|1|20191213|233601|1|A|2019121300000336507760041111111|");//
                data2.append("|1|2019121300000336507760041111111|1|1|1|1|");
                data2.append("\r\n");
                fw2.write(data2.toString());
                data2.delete(0, data2.length());
            }
            return true;
        } catch (Exception e1) {
            e1.printStackTrace();
            return false;
        } finally{
            long end0 = System.currentTimeMillis();
            System.out.println("BufferedOutputStream执行耗时:" + (end0 - begin0) + " 毫秒");
        }
    }

    public static void main(String args[]){

/*
file：文件名字
code需要生成的内容
size ：代表生成的文件的大小,单位只能是：G,K,M ,如果想表示B，请用0.1K
 */
        Scanner scan=new Scanner(System.in);
        int  size=5000000;
        int threadnum=2;
        final CountDownLatch cd=new CountDownLatch(threadnum);
        try {
          fw = new FileWriter(new File("zxm.dat"),true);  // 为了这张表数据ANA_VDT_CMB_T
            //fw2 = new FileWriter(new File("zxm2.dat"),true);  // 为了这张表数据ANA_VDT_CMB_T
        } catch (IOException e) {
            e.printStackTrace();
        }

        for(int j=0;j<threadnum;j++) {
            System.out.println("开启线程:"+String.valueOf(j));

            new Thread(new Runnable() {

                public void run() {

                    boolean result=false;
                    boolean result2=false;
                    while (true) {

                        result=  new Writefile2().writefile(size);
                        //result2=  new Writefile2().writefile2(size);
                        if(result){
                            System.out.println("执行写文件成功");
                            break;
                        }
                        if(!result){
                            System.out.println("写文件失败");
                            break;
                        }
                    }
                    cd.countDown();
                }

            }).start();
        }
        try {
            cd.await();
            if(fw!=null){
                fw.close();
            }
            if(fw2!=null){
                fw2.close();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}