文件读写操作

import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.LineNumberReader;
import java.text.SimpleDateFormat;
import java.util.Date;

/**
 * 这是一个与日志读写有关的类，定义了一些通用的方法
 *
 * @author Devon
 *
 */
public class LogReaderWriter {
    
    public static int getTotalLines(String fileName) throws IOException {
        FileReader in = new FileReader(fileName);
        LineNumberReader reader = new LineNumberReader(in);
        String strLine = reader.readLine();
        int totalLines = 0;
        while (strLine != null) {
            totalLines++;
            strLine = reader.readLine();
        }
        reader.close();
        in.close();
        return totalLines;
    }

    public static void readForPage(String filePath, int pageNo, int pageSize) throws IOException {
        File file = new File(filePath);
        FileReader in = new FileReader(file);
        LineNumberReader reader = new LineNumberReader(in);
        String s = "";
        /*if (lineNumber <= 0 || lineNumber > getTotalLines(sourceFile)) {  
         System.out.println("不在文件的行数范围(1至总行数)之内。");  
         System.exit(0);  
         }  */
        int startRow = (pageNo - 1) * pageSize + 1;
        int endRow = pageNo * pageSize;
        int lines = 0;
        System.out.println("startRow:" + startRow);
        System.out.println("endRow:" + endRow);
        while (s != null) {
            lines++;
            s = reader.readLine();
            if (lines >= startRow && lines <= endRow) {
                System.out.println("line:" + lines + ":" + s);
            }
        }
        reader.close();
        in.close();
    }

    /**
     *
     * @param filePath 文件路径的字符串表示形式
     * @param KeyWords 查找包含某个关键字的信息：非null为带关键字查询；null为全文显示
     * @return 当文件存在时，返回字符串；当文件不存在时，返回null
     */
    public static String readFromFile(String filePath, String KeyWords) {
        StringBuffer stringBuffer = null;
        File file = new File(filePath);
        if (file.exists()) {
            stringBuffer = new StringBuffer();
            FileReader fileReader = null;
            BufferedReader bufferedReader = null;
            String temp;
            try {
                fileReader = new FileReader(file);
                bufferedReader = new BufferedReader(fileReader);
                while ((temp = bufferedReader.readLine()) != null) {
                    if (KeyWords == null) {
                        stringBuffer.append(temp).append("
");
                    } else {
                        if (temp.contains(KeyWords)) {
                            stringBuffer.append(temp).append("
");
                        }
                    }
                }
            } catch (FileNotFoundException e) {
                //e.printStackTrace();
            } catch (IOException e) {
                //e.printStackTrace();
            } finally {
                try {
                    if (fileReader != null) {
                        fileReader.close();
                    }
                } catch (IOException e) {
                    //e.printStackTrace();
                }
                try {
                    if (bufferedReader != null) {
                        bufferedReader.close();
                    }
                } catch (IOException e) {
                    //e.printStackTrace();
                }
            }
        }
        if (stringBuffer == null) {
            return null;
        } else {
            return stringBuffer.toString();
        }

    }

    /**
     * 将指定字符串写入文件。如果给定的文件路径不存在，将新建文件后写入。
     *
     * @param log 要写入文件的字符串
     * @param filePath 文件路径的字符串表示形式，目录的层次分隔可以是“/”也可以是“\”
     * @param isAppend true：追加到文件的末尾；false：以覆盖原文件的方式写入
     * @return 文件是否写入成功
     */
    public static boolean writeIntoFile(String log, String filePath, boolean isAppend) {
        boolean isSuccess = true;
        File file = new File(filePath);
        if (!file.exists()) {
            createNewFile(filePath);
        }
        //将logs写入文件
        FileWriter fileWriter = null;
        try {
            fileWriter = new FileWriter(file, isAppend);
            fileWriter.write(log + "
");
            fileWriter.flush();
        } catch (IOException e) {
            isSuccess = false;
            //e.printStackTrace();
        } finally {
            try {
                if (fileWriter != null) {
                    fileWriter.close();
                }
            } catch (IOException e) {
                //e.printStackTrace();
            }
        }

        return isSuccess;
    }

    /**
     * 创建文件，如果该文件已存在将不再创建（即不起任何作用）
     *
     * @param filePath 要创建文件的路径的字符串表示形式，目录的层次分隔可以是“/”也可以是“\”
     * @return 创建成功将返回true；创建不成功则返回false
     */
    public static boolean createNewFile(String filePath) {
        boolean isSuccess;
        //创建文件
        File file = new File(filePath);
        try {
            isSuccess = file.createNewFile();
        } catch (IOException e) {
            isSuccess = false;
        }
        return isSuccess;
    }

    public static void main(String[] args) {
        String filename = "b.txt";
        
        String str;
        for (int i = 0; i < 100; i++) {
            str = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss").format(new Date()) + " - 插入数据" + i;
            writeIntoFile(str, filename, true);
        }
        
        try {
            long time = System.currentTimeMillis();
            int count = getTotalLines(filename);
            System.out.println(System.currentTimeMillis() - time);
            
            System.out.println("当前文件总行数: " + count);
            readForPage(filename, 10, 10);
        } catch (IOException ex) {
           ex.printStackTrace();
        }
    }
}