File类

运用File类进行文件操作
    file.getPath()        相对路径
    file.getAbsolutePath()    绝对路径
路径：/  \
方法： 
    创建文件
    exists()
    createNewFile()
    
    删除文件
    exists()
    delete()
    
    获取文件相关信息
    isFile()
    isDirectory()
    getName()
    getPath()
    getAbsolutePath()
    length()
范例1：
public class FileMethods {
    //创建文件
    public void creatFile(File file){
        if (!file.exists()) {
            try {
                file.createNewFile();
                System.out.println("文件创建成功");
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
    
    //查看文件信息
    public void showFileInfo(File file){
        if (file.exists()) {
            if (file.isFile()) {
                System.out.println("文件名：" + file.getName());
                System.out.println("文件绝对路径：" + file.getAbsolutePath());
                System.out.println("文件相对路径：" + file.getPath());
                System.out.println("文件大小（字节）：" + file.length());
            }
            
            if (file.isDirectory()) {
                System.out.println("这是一个目录");
            }
        }
    }
    
    //删除文件
    public void deleteFile(File file){
        if (file.exists()) {
            file.delete();
            System.out.println("文件删除成功");
        }
    }
    
    //测试
    public static void main(String[] args) {
        //调用方法，创建方法的对象
        FileMethods fm = new FileMethods();
        //创建文件对象
//        File file = new File("e:" + File.separator + "Java实训课总结" + File.separator + "2016.3.26" + File.separator + "FileDemo.txt");
        File file = new File("FileDemo.txt");
        fm.creatFile(file);
        fm.showFileInfo(file);
        fm.deleteFile(file);
    }
}    

范例2：
public class FileMethod {
    //判断文件夹是否存在
    public String existFile(String pathName){
        File file = new File(pathName);
        if (!file.exists()) {
            return null;
        } else {
            return pathName;
        }
    }
    
    //显示文件信息
    public void showFileInfo(String pathName){
        File file = new File(pathName);
        String str = existFile(pathName);
        if (str != null) {
            file.getAbsolutePath();
            System.out.println("文件名：" + file.getName());
            System.out.println("文件大小：" + file.length());
            System.out.println("文件绝对路径：" + file.getAbsolutePath());
            System.out.println("文件相对路径：" + file.getPath());
//            System.out.println("文件大小(单位：字节)：" + new BigDecimal((double)file.length()/1024/1024).divide(new BigDecimal(1), 2, BigDecimal.ROUND_HALF_UP) + "M");
        }
    } 
    
    //分割类
    public long unitSize = 0;//每个小文件的大小
    public String targetDir = null;//分割后小文件所在的文件夹
    
    public int cutFile(String pathName) throws IOException{
        File file = new File(pathName);
        String str = existFile(pathName);
        long size = file.length();//总字节数
        int count = 0;//小文件数
        long pos = 0;//当前位置
        long last = 0;//剩余字节数
        DataInputStream dis = new DataInputStream(new BufferedInputStream(new FileInputStream(pathName),(int)unitSize));
        byte[] data = new byte[(int)this.unitSize];
        while (pos < size) {
            count++;
            last = size - pos;
            if (last < this.unitSize) {
                data = new byte[(int)last];
            }
            dis.read(data);
            pos = pos + data.length;
            //写小文件
            try {
                RandomAccessFile raFile = new RandomAccessFile(this.targetDir + "-" + count,"rw");
                System.out.println(this.targetDir + "-" + count);
                raFile.write(data);
                raFile.close();
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }    
        }
        //记载小文件数
        File file2 = new File(this.targetDir + "_count");
        BufferedWriter bw = new BufferedWriter(new FileWriter(file2));
        String str2 = (new Integer(count)).toString();
        bw.write(str2, 0, str2.length());
        bw.flush();
        bw.close();
        return count;
    }

    public long getUnitSize() {
        return unitSize;
    }

    public void setUnitSize(long unitSize) {
        this.unitSize = unitSize;
    }

    public String getTargetDir() {
        return targetDir;
    }

    public void setTargetDir(String targetDir) {
        this.targetDir = targetDir;
    }
}

//测试
public class SegmentationTxt {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        FileMethod fm = new FileMethod();
        //1.输入文件路径
        System.out.println("请输入文件路径：");
        String pathName = input.next();
        File file = new File(pathName);
        String str = fm.existFile(pathName);
        while (str == null) {
            System.out.println("文件不存在！");
            System.out.println("请输入文件路径：");
            pathName = input.next();
            str = fm.existFile(pathName);
        }
        System.out.println("======文件信息=====");
        //2.打印文件信息
        fm.showFileInfo(pathName);
        //3.分割文件
        System.out.println("请输入文件分割的大小（单位byte）：");
        int dividNum = input.nextInt();
        System.out.println("开始分割......");
        try {
            Thread.sleep(2000);
            fm.setUnitSize(dividNum);
            fm.setTargetDir(pathName);
            fm.cutFile(pathName);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}