动手动脑——流与文件

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 filesoperation;

import java.io.File;
import java.io.IOException;
import java.nio.file.FileVisitResult;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.SimpleFileVisitor;
import java.nio.file.attribute.BasicFileAttributes;


public class SearchSmallFiles extends SimpleFileVisitor<Path> {
    public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
        File f = new File(file.toString());
        if(f.length() > 1024 * 1024 *1)
            System.out.println(file.toString() + "大小为:" + (double)f.length()/1024/1024 + "M。");
        return FileVisitResult.CONTINUE;
    }
    public static void main(String[] args) {
        Path fileDirPath=Paths.get("F:\学习\作业\Java");
        SearchSmallFiles visitor=new SearchSmallFiles();
        try {
            Files.walkFileTree(fileDirPath, visitor);
        } catch (IOException e) {
            e.printStackTrace();
        }    
    }
}

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 filesoperation;

import java.io.IOException;
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 SearchTXTAndJAVA extends SimpleFileVisitor<Path> {
    public FileVisitResult visitFile(Path file, BasicFileAttributes attrs)
            throws IOException {
        Path name=file.getFileName();
        if(matcher.matches(name)){
            foundPaths.add(file);
        }
        return FileVisitResult.CONTINUE;
    }
    private PathMatcher matcher;    
    public ArrayList<Path> foundPaths=new ArrayList<>();
    public SearchTXTAndJAVA(String pattern){
        matcher=FileSystems.getDefault().getPathMatcher("glob:"+pattern);    
    }    
    public static void main(String[] args) {
        Path fileDir=Paths.get("F:\学习\作业\Java");
        SearchTXTAndJAVA finder1 = new SearchTXTAndJAVA("*.txt");
        SearchTXTAndJAVA finder2 = new SearchTXTAndJAVA("*.java");
        try {
            Files.walkFileTree(fileDir, finder1);
            ArrayList<Path> foundFiles1=finder1.foundPaths;
            if(foundFiles1.size()>0){
                for (Path path : foundFiles1) {
                System.out.println(path.toRealPath(LinkOption.NOFOLLOW_LINKS));
                }
            }else {
                System.out.println("未发现".txt"文件!");
            }    
            Files.walkFileTree(fileDir, finder2);
            ArrayList<Path> foundFiles2=finder2.foundPaths;
            if(foundFiles2.size()>0){
                for (Path path : foundFiles2) {
                System.out.println(path.toRealPath(LinkOption.NOFOLLOW_LINKS));
                }
            }else {
                System.out.println("未发现".java"文件!");
            }        
        } catch (IOException e) {    
            e.printStackTrace();
        }
    }
}

3.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 filesoperation;

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
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 SearchTheTXT extends SimpleFileVisitor<Path> {
    private PathMatcher matcher;    
    public ArrayList<Path> foundPaths=new ArrayList<>();
    public SearchTheTXT(String pattern){
        matcher=FileSystems.getDefault().getPathMatcher("glob:"+pattern);    
    }
    public FileVisitResult visitFile(Path file, BasicFileAttributes attrs)throws IOException {
        Path name = file.getFileName();
        if(matcher.matches(name)){
            BufferedReader br = new BufferedReader(new FileReader(file.toString()));
            String str;
            boolean isTheTXT = false;
            while((str = br.readLine()) != null) {
                if(str.indexOf("life") != -1) {
                    isTheTXT = true;
                    break;
                }
            }
            if(isTheTXT)
                foundPaths.add(file);
            br.close();
        }
        return FileVisitResult.CONTINUE;
    }
    public static void main(String[] args) {
        Path fileDir=Paths.get("F:\学习\作业");
        SearchTheTXT finder = new SearchTheTXT("*.txt");
        try {
            Files.walkFileTree(fileDir, finder);
            ArrayList<Path> foundFiles1=finder.foundPaths;
            if(foundFiles1.size()>0){
                for (Path path:foundFiles1) {
                    System.out.println(path.toRealPath(LinkOption.NOFOLLOW_LINKS));
                }
            }else {
                System.out.println("未发现含有"life"的".txt"文件!");
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}