文件操作工具

r囧r小猫 2022-01-11 02:59 279阅读 0赞

import java.io.*;
    import java.nio.ByteBuffer;
    import java.nio.MappedByteBuffer;
    import java.nio.channels.FileChannel;
    
    /**
     * DateTime: 2016/9/18 21:04
     * 功能：文件操作工具
     * 思路：
     */
    public class FileUtil {
        public static void main(String[] args) {
    
        }
    
        /**
         *创建目录
         * @param destDirName 目标目录名
         * @return
         */
        public static boolean createDir(String destDirName){
            File dir=new File(destDirName);
            if(dir.exists()){
                return  false;
            }
            if(!destDirName.endsWith(File.separator)){  //如果结尾没有文件分隔符
                destDirName+=File.separator;
            }
            //创建单个目录
            if(dir.mkdir()){
                return true;
            }else return false;
    
        }
    
        /**
         * 删除文件
         * @param filePathAndName   文件路径及名称 如c:/fqf.txt
         */
        public static void delFile(String filePathAndName){
            try {
                String filePath=filePathAndName;
                filePath=filePath.toString();
                File myDelFile=new File(filePath);
                myDelFile.delete();
    
            }catch ( Exception e ){
                System.out.println("删除文件出错");
                e.printStackTrace();
            }
        }
    
        /**
         * 读取到字节数组0
         * @param filePath  路径
         * @return
         * @throws IOException
         */
        public static byte[] getContent(String filePath) throws IOException{
            File file=new File(filePath);
            long fileSize=file.length();
            if(fileSize>Integer.MAX_VALUE){
                System.out.println("文件太大....");
                return null;
            }
    
            FileInputStream fi=new FileInputStream(file);
            byte[] buffer=new byte[(int)fileSize];
            int offset=0;
            int numRead=0;
            while ( offset<buffer.length &&(numRead=fi.read(buffer,offset,buffer.length-offset))>=0 ){
                offset+=numRead;
            }
            //确保所有数据均被读完
            if(offset!=buffer.length){
                throw new IOException("不能全部读取文件:"+file.getName());
            }
            fi.close();
            return  buffer;
        }
    
        /**
         * 读取到字节数组1
         * @param filePath
         * @return
         * @throws IOException
         */
        public static byte[] toByteArray(String filePath) throws IOException{
            File f=new File(filePath);
            if(!f.exists()){
                throw new FileNotFoundException("文件不能找到:"+filePath);
            }
            ByteArrayOutputStream bos=new ByteArrayOutputStream((int)f.length());
            BufferedInputStream in=null;
    
            try {
                in=new BufferedInputStream(new FileInputStream(f));
                int buf_size=1024;
                byte[] buffer=new byte[buf_size];
                int len=0;
                while ( -1!=(len=in.read(buffer,0,buf_size)) ){
                    bos.write(buffer,0,len);
                }
                return bos.toByteArray();
            }catch ( IOException e ){
                e.printStackTrace();
                throw e;
            }finally {
                in.close();
                bos.close();
            }
    
        }
    
    
        public static byte[] toByteArray2(String filePath) throws IOException{
            File f=new File(filePath);
            if(!f.exists()){
                throw new FileNotFoundException("文件不能找到:"+filePath);
            }
            FileChannel channel=null;   //Java NIO中的FileChannel是一个连接到文件的通道。可以通过文件通道读写文件。FileChannel无法设置为非阻塞模式，它总是运行在阻塞模式下。
            FileInputStream fs=null;
            try {
                fs=new FileInputStream(f);
                channel=fs.getChannel();
                ByteBuffer byteBuffer=ByteBuffer.allocate((int)channel.size());
                while ( (channel.read(byteBuffer)) >0 ){
    
                }
                return byteBuffer.array();
            }catch ( IOException e ){
                e.printStackTrace();
                throw e;
            }finally {
                channel.close();
                fs.close();
            }
    
        }
    
        /**
         * Mapped File way MappedByteBuffer 可以在处理大文件时，提升性能
         * @param filePath
         * @return
         * @throws IOException
         */
        public static byte[] toByteArray3(String filePath) throws IOException{
            FileChannel fc=null;
            RandomAccessFile rf=null;
    
            try {
                rf=new RandomAccessFile(filePath,"r");
                fc=rf.getChannel();
                MappedByteBuffer byteBuffer=fc.map(FileChannel.MapMode.READ_ONLY,0,fc.size()).load();
                byte[] result=new byte[(int)fc.size()];
                if(byteBuffer.remaining()>0){
                    byteBuffer.get(result,0,byteBuffer.remaining());
                }
                return result;
            }catch ( IOException e ){
                e.printStackTrace();
                throw e;
            }finally {
                rf.close();
                fc.close();
            }
    
        }
    
    
    }