Java文件与类动手动脑

动手动脑1：

使用Files. walkFileTree()找出指定文件夹下所有大于指定大小（比如1M）的文件。

package classJava;

import java.io.IOException;
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.Paths;
import java.nio.file.attribute.BasicFileAttributes;
import java.util.EnumSet;

public class titletwo implements FileVisitor<Object> {
 private long accepted_size;
 public  void titletwo(String glob,long accepted_size) {
      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 = 28672;
       Path fileTree = Paths.get("D:/");
       titletwo walk=new titletwo();
       EnumSet<FileVisitOption> opts=EnumSet.of(FileVisitOption.FOLLOW_LINKS);
       System.out.println("D盘中大小等于28672字节的文件有");
       Files.walkFileTree(fileTree, opts, Integer.MAX_VALUE, walk);
   }
}

使用Files. walkFileTree()找出指定文件夹下所有扩展名为.txt和.java的文件。

package classJava;

import java.io.IOException;
import java.nio.file.FileSystems;
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 titletwo {

    public static void main(String args[]) throws IOException {
        String glob = "glob:**/*.{java,txt}";
        String path = "D:/";
        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)) {
                    System.out.println(path);
                }
                return FileVisitResult.CONTINUE;
            }

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

}

使用Files. walkFileTree()找出指定文件夹下所有包容指定字符串的txt文件。

package classJava;

import java.io.IOException;
import java.io.*;
import java.nio.file.FileSystems;
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 titletwo {

    public static void main(String args[]) throws IOException {
        String glob = "glob:**/*.txt";
        String path = "D:\\wenjian";
        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.equals("account"))//若读取的内容等于“account"则输出文件名
                   {
                         System.out.println(path);
                         break;
                   }

                  }
                }
                  return FileVisitResult.CONTINUE;
            }

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

}

动手动脑2：

java.nio.file.WatchService文件系统监视服务的接口类，它的具体实现由监视服务提供者负责加载。

java.nio.file.Watchable 实现了 java.nio.file.Watchable 的对象才能注册监视服务 WatchService。java.nio.file.Path实现了 watchable 接口，后文使用 Path 对象注册监视服务。

java.nio.file.WatchKey 该类代表着 Watchable 对象和监视服务 WatchService 的注册关系。WatchKey 在 Watchable 对象向 WatchService 注册的时候被创建。它是 Watchable 和 WatchService 之间的关联类。

原文地址：https://www.cnblogs.com/vvxvv/p/11808524.html