基于Java IO API实现文件查找工具

/**
 * Sample code that finds files that match the specified glob pattern.
 * For more information on what constitutes a glob pattern, see
 * https://docs.oracle.com/javase/tutorial/essential/io/fileOps.html#glob
 *
 * The file or directories that match the pattern are printed to
 * standard out.  The number of matches is also printed.
 *
 * When executing this application, you must put the glob pattern
 * in quotes, so the shell will not expand any wild cards:
 *              java Find . -name "*.java"
 */

import java.io.*;
import java.nio.file.*;
import java.nio.file.attribute.*;
import static java.nio.file.FileVisitResult.*;
import static java.nio.file.FileVisitOption.*;
import java.util.*;


public class Find {

    public static class Finder
        extends SimpleFileVisitor<Path> {

        private final PathMatcher matcher;
        private int numMatches = 0;

        Finder(String pattern) {
            matcher = FileSystems.getDefault()
                    .getPathMatcher("glob:" + pattern);
        }

        // Compares the glob pattern against
        // the file or directory name.
        void find(Path file) {
            Path name = file.getFileName();
            if (name != null && matcher.matches(name)) {
                numMatches++;
                System.out.println(file);
            }
        }

        // Prints the total number of
        // matches to standard out.
        void done() {
            System.out.println("Matched: "
                + numMatches);
        }

        // Invoke the pattern matching
        // method on each file.
        @Override
        public FileVisitResult visitFile(Path file,
                BasicFileAttributes attrs) {
            find(file);
            return CONTINUE;
        }

        // Invoke the pattern matching
        // method on each directory.
        @Override
        public FileVisitResult preVisitDirectory(Path dir,
                BasicFileAttributes attrs) {
            find(dir);
            return CONTINUE;
        }

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

    static void usage() {
        System.err.println("java Find <path>" +
            " -name \"<glob_pattern>\"");
        System.exit(-1);
    }

    public static void main(String[] args)
        throws IOException {

        if (args.length < 3 || !args[1].equals("-name"))
            usage();

        Path startingDir = Paths.get(args[0]);
        String pattern = args[2];

        Finder finder = new Finder(pattern);
        Files.walkFileTree(startingDir, finder);
        finder.done();
    }
}

$ java Find . -name "*.java"

public static void main(String[] args) throws IOException {
    if (args.length < 3 || !args[1].equals("-name"))
        usage();

    Path startingDir = Paths.get(args[0]);
    String pattern = args[2];

    Finder finder = new Finder(pattern);
    Files.walkFileTree(startingDir, finder);
    finder.done();
}

public static class Finder extends SimpleFileVisitor<Path> {

matcher = FileSystems.getDefault().getPathMatcher("glob:" + pattern);

void find(Path file) {
    Path name = file.getFileName();
    if (name != null && matcher.matches(name)) {
        numMatches++;
        System.out.println(file);
    }
}

public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) {
    find(dir); // 匹配目录名
    return CONTINUE;
}

public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) {
    find(file);
    return CONTINUE;
}

public FileVisitResult visitFileFailed(Path file, IOException exc) {
    System.err.println(exc);
    return CONTINUE;
}

void done() {
    System.out.println("Matched: " + numMatches);
}

$ java Find . -name "*.html"