Java课堂动手动脑

　　　　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：

代码：

package test;

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.PathMatcher;
import java.nio.file.Paths;
import java.nio.file.attribute.BasicFileAttributes;
import java.util.EnumSet;
public class KnownSize implements FileVisitor {
 private final PathMatcher matcher;
 private final long accepted_size;
 public KnownSize(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
    Path fileTree = Paths.get("C:/");
    KnownSize walk=new KnownSize(glob, size);
    EnumSet opts=EnumSet.of(FileVisitOption.FOLLOW_LINKS);
    System.out.println("C盘中大小等于1M的文件有");
    Files.walkFileTree(fileTree, opts, Integer.MAX_VALUE, walk);
   }
}

运行结果：

　　　　2.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 test;

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 WalkFileTree {
        public static void main(String[] args) throws IOException {
            String glob ="glob:**/*.{java,txt}";//采用组模式查找拓展名为.java和.txt的文件
            String path ="E:/";//想要查询的目录
            match(glob,path);
        }

        public static void match(String glob,String location)throws IOException{
            final PathMatcher pathmatcher =FileSystems.getDefault().getPathMatcher(glob);//新建pathmatcher对象用FileSystems.getDefault().getPathMatcher()方法接收匹配的字符串，返回一个可用的pathmatcher对象，然后进行匹配工作
            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;
            }});
        }
}

运行结果：