Java讀取大文件方法

2019-11-14 15:29:45

字體：大中小

供稿：網(wǎng)友

需求：實(shí)際開發(fā)中讀取文本文件的需求還是很多，如讀取兩個(gè)系統(tǒng)之間FTP發(fā)送文件，讀取后保存到數(shù)據(jù)庫中或日志文件的數(shù)據(jù)庫中保存等。

為了測試首先利用數(shù)據(jù)庫SQL生成大數(shù)據(jù)文件。

規(guī)則是編號|姓名|手機(jī)號，如 10|張10|13900000010

利用下面語句可以生成1,000,000條數(shù)據(jù)。生成的數(shù)據(jù)保存到 D://test//customer_info.txt 文件里面。

SELECT LEVEL||'|'||'張'||LEVEL||'|'||(13900000000+LEVEL)  FROM DUAL CONNECT BY LEVEL < 1000000;

利用java程序讀取剛生成的文件。

實(shí)現(xiàn)如下：

package com.test.common.util;import java.io.BufferedReader;import java.io.File;import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.FileReader;import java.io.IOException;import java.util.Scanner;import org.apache.commons.io.FileUtils;import org.apache.commons.io.LineIterator;public class HandleTextFile {        // 使用commons-io.jar包的FileUtils的類進(jìn)行讀取    public static void readTxtFileByFileUtils(String fileName) {        File file = new File(fileName);        try {            LineIterator lineIterator = FileUtils.lineIterator(file, "UTF-8");            while (lineIterator.hasNext()) {                String line = lineIterator.nextLine();                System.out.PRintln(line);            }        } catch (IOException e) {            e.printStackTrace();        }    }        // 使用Scanner進(jìn)行讀取    public static void readTxtByScanner(String fileName) {        FileInputStream fileInputStream = null;         Scanner scanner = null;                try {            fileInputStream = new FileInputStream(fileName);            scanner = new Scanner(fileInputStream, "UTF-8");            while (scanner.hasNext()) {                String line = scanner.nextLine();                System.out.println(line);            }        } catch (FileNotFoundException e) {            e.printStackTrace();        } finally {            if (fileInputStream != null) {                try {                    fileInputStream.close();                } catch (IOException e) {                    e.printStackTrace();                }            }            if (scanner != null) {                scanner.close();            }        }            }    // 使用cache進(jìn)行讀取    public static void readTxtByStringBuffer(String fileName) throws IOException {        File file = new File(fileName);                BufferedReader reader = null;                try {            reader = new BufferedReader(new FileReader(file), 10 * 1024 * 1024);            String stringMsg = null;            while ((stringMsg = reader.readLine()) != null) {                System.out.println(stringMsg);            }            reader.close();        } catch (FileNotFoundException e) {            e.printStackTrace();        }     }        public static void main(String[] args) {        try {            HandleTextFile.readTxtByStringBuffer("D://test//customer_info.txt");        } catch (IOException e) {            e.printStackTrace();        }    }}