关于对文件的操作

（1）遍历指定文件夹，输出带有.txt和.java的文件

package Demo1;

import java.io.IOException;
import java.nio.file.FileSystem;
import java.nio.file.FileSystems;
import java.nio.file.FileVisitResult;
import java.nio.file.Files;
import java.nio.file.LinkOption;
import java.nio.file.Path;
import java.nio.file.PathMatcher;
import java.nio.file.Paths;
import java.nio.file.SimpleFileVisitor;
import java.nio.file.attribute.BasicFileAttributes;
import java.util.ArrayList;


public class FileFinder extends SimpleFileVisitor<Path> {



    @Override
    public FileVisitResult visitFile(Path file, BasicFileAttributes attrs)
            throws IOException {
        Path name=file.getFileName();
        System.out.println("Examining "+name);
        if(matcher.matches(name)){
            foundPaths.add(file);
        }
        return FileVisitResult.CONTINUE;
    }

    private PathMatcher matcher;
    
    public ArrayList<Path> foundPaths=new ArrayList<>();
    
    public FileFinder(String pattern){
        matcher=FileSystems.getDefault().getPathMatcher("glob:"+pattern);    
    }
    
    public static void main(String[] args) {
        Path fileDir=Paths.get("E:\Eclipse IDE for java developers");
        FileFinder finder1=new FileFinder("*.java");
        FileFinder finder2=new FileFinder("*.txt");
        try {
            Files.walkFileTree(fileDir, finder1);
            Files.walkFileTree(fileDir, finder2);
            ArrayList<Path> foundFiles=finder1.foundPaths;
            ArrayList<Path> foundFiles1=finder2.foundPaths;
            if(foundFiles.size()>0){
                for (Path path : foundFiles) {
                System.out.println(path.toRealPath(LinkOption.NOFOLLOW_LINKS));
                }
            }
            else {
                System.out.println("No files were found!");
            }
            if(foundFiles1.size()>0){
                for (Path path : foundFiles1) {
                System.out.println(path.toRealPath(LinkOption.NOFOLLOW_LINKS));
                }
            }
            else {
                System.out.println("No files were found!");
            }
            
        } catch (IOException e) {
        
            e.printStackTrace();
        }

    }

}

输出结果：

 （2）输出大小为1M的文件

import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.file.FileSystems;
import java.nio.file.FileVisitOption;
import java.nio.file.FileVisitResult;
import java.nio.file.FileVisitor;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.PathMatcher;
import java.nio.file.Paths;
import java.nio.file.attribute.BasicFileAttributes;
import java.util.EnumSet;
public class Search implements FileVisitor {
 private final PathMatcher matcher;
 private final long accepted_size;
 public Search(String glob,long accepted_size) {
      matcher= FileSystems.getDefault().getPathMatcher("glob:" +glob);
      this.accepted_size=accepted_size; 
    }
   void search(Path file) throws IOException {
    long size = (Long) Files.getAttribute(file, "basic:size");
    if(size ==accepted_size) {
     System.out.println(file);
    }
   }
   @Override
   public FileVisitResult postVisitDirectory(Object dir, IOException exc)throws IOException {
    return FileVisitResult.CONTINUE;
   }
   @Override
   public FileVisitResult preVisitDirectory(Object dir, BasicFileAttributes attrs)throws IOException {
    return FileVisitResult.CONTINUE;
   }
   @Override
   public FileVisitResult visitFile(Object file, BasicFileAttributes attrs)throws IOException {
  search((Path) file);
     return  FileVisitResult.CONTINUE;
  }
   @Override
   public FileVisitResult visitFileFailed(Object file, IOException exc)throws IOException {
  return FileVisitResult.CONTINUE;
   }
   public static void main(String[] args) throws IOException{
    String glob= "*.jpg";
    long size = 1048576;//1M=1024k=1048576字节
    RandomAccessFile f = new RandomAccessFile("E:\f1.txt", "rw");
    f.setLength(1024 * 1024);  //设置其大小为1M。
    Path fileTree = Paths.get("E:\f1");
    Search walk=new Search(glob, size);
    EnumSet opts=EnumSet.of(FileVisitOption.FOLLOW_LINKS);
    System.out.println("E盘f1文件中中大小等于1M的文件有");
    Files.walkFileTree(fileTree, opts, Integer.MAX_VALUE, walk);
   }
}

结果：

 

 由于没有恰好1M的文件，所以我用了代码：

RandomAccessFile f = new RandomAccessFile("E:\f1.txt", "rw");
    f.setLength(1024 * 1024);  //设置其大小为1M。

将此文件设为恰好1M。

（3）找出包容指定字符串的TXT文件

　　

import java.nio.file.FileVisitResult;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.PathMatcher;
import java.nio.file.Paths;
import java.nio.file.SimpleFileVisitor;
import java.nio.file.attribute.BasicFileAttributes;

public class filesearch {
     public static void main(String args[]) throws IOException {
            String glob = "glob:**/*.txt";
            String path = "E:\f1";
            match(glob, path);
        }

        public static void match(String glob, String location) throws IOException {

            final PathMatcher pathMatcher = FileSystems.getDefault().getPathMatcher( glob);

            Files.walkFileTree(Paths.get(location), new SimpleFileVisitor<Path>() {

                @Override
                public FileVisitResult visitFile(Path path,BasicFileAttributes attrs) throws IOException {
                    if (pathMatcher.matches(path)) {
                     BufferedReader reader =Files.newBufferedReader(path);//读取文件内的内容 
                      String line=null;
                      while((line = reader.readLine()) !=null) {
                       if(line=="ABC")//若读取的内容等于“ABC"则输出文件名
                       {
                             System.out.println(path);
                             break;
                       }
                       else {
                           System.out.println("没有对应文件");
                       }
                      }
                    }
                      return FileVisitResult.CONTINUE;
                }

                @Override
                public FileVisitResult visitFileFailed(Path file, IOException exc)
                        throws IOException {
                    return FileVisitResult.CONTINUE;
                }
            });
        }

}

结果：

（5）计算文件总容量

package Demo1;

import java.io.File;
import java.util.ArrayList;

public class Size {
    static long size = 0;
    private static ArrayList<String> filelist = new ArrayList<String>();

    public static void main(String[] args) {
        Size s = new Size();
        String filePath = "E:\f1";
        s.getFiles(filePath);

    }
    void getFiles(String filePath) {

        File root = new File(filePath);
        File[] files = root.listFiles();
        for (File file : files) {
            if (file.isDirectory()) {
                getFiles(file.getAbsolutePath());
                filelist.add(file.getAbsolutePath());

            } else {
                size += file.getAbsolutePath().length();
            }
        }
        System.out.println("总容量是" + size);

    }

}

结果：