（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
     
       {    @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
      
        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
       
         foundFiles=finder1.foundPaths;            ArrayList
        
          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
     
      () {                @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
     
       filelist = new ArrayList
      
       ();    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：