Java编程思想：File类getCanonicalFile()方法，listFile()方法

import java.io.IOException;import java.util.*;import java.util.regex.Pattern;import java.io.File;import java.io.FilenameFilter;public class Test {    public static void main(String[] args) {//        DirectoryDemo.test();        ProcessFileTest.test();        ProcessFileTest.test2();    }}/*    local():产生由本地目录中的文件构成的File对象数组    walk():产生给定目录下的由整个目录书中所有文件构成的List<File> */class Directory {    public static File[] local(File dir, String regex) {        return dir.listFiles(new FilenameFilter() {            Pattern pattern = Pattern.compile(regex);            @Override            public boolean accept(File dir, String name) {                return pattern.matcher(name).matches();            }        });    }    public static class TreeInfo implements Iterable<File>{        public List<File> dirs = new ArrayList<>();        public List<File> files = new ArrayList<>();        public TreeInfo() {        }        public void addAll(TreeInfo infos) {            this.dirs.addAll(infos.dirs);            this.files.addAll(infos.files);        }        @Override        public Iterator<File> iterator() {            return files.iterator();        }        public String toString() {            return "dirs: " + PPrint.pformat(dirs) + "\n\nfiles:" + PPrint.pformat(files);        }    }    public static File[] local(String path, String regex) {        return local(new File(path),regex);    }    private static TreeInfo recurseDirs(File startDir, String regex) {        TreeInfo result = new TreeInfo();        for (File item : startDir.listFiles()) {            if (item.isDirectory()) {                result.dirs.add(item);                result.addAll(recurseDirs(item,regex));            } else {                //这个地方的写法和我之前看到的不太一样                if (item.getName().matches(regex)) {                    result.files.add(item);                }            }        }        return result;    }    public static TreeInfo walk(String start, String regex) {        return recurseDirs(new File(start),regex);    }    public static TreeInfo walk(File start, String regex) {        return recurseDirs(start, regex);    }    public static TreeInfo walk(String start) {        return recurseDirs(new File(start), ".*");    }}class PPrint {    public static String pformat(Collection<?> collection) {        if (collection.size() == 0) {            return "[]";        }        StringBuilder result = new StringBuilder("[");        for (Object elem : collection) {            if (collection.size() != 1) {                result.append("\n   ");            }            result.append(elem);        }        if (collection.size() != 1) {            result.append("\n");        }        result.append("]");        return  result.toString();    }    public static void pprint(Collection<?> c) {        System.out.println(pformat(c));    }    public static void pprint(Object[] objects) {        System.out.println(pformat(Arrays.asList(objects)));    }}class DirectoryDemo {    public static void test() {        PPrint.pprint(Directory.walk(".").dirs);    }}/*    创建一个工具，它可以在目录中穿行，并且根据Strategy对象来处理这些目录中的文件    书中案例的逻辑：        1.针对上一个案例中walk方法计算出来的所有文件，执行一个策略方法 *///书中原代码：/*    ProcessFiles的工作是：执行查找具有特定扩展名的文件的所有工作    Strategy的工作是：查找到指定的文件后，执行某个指定的算法 */class ProcessFiles {    public interface Strategy {        void process(File file);    }    private Strategy strategy;    private String ext;    public ProcessFiles(Strategy s,String ext){        this.strategy=s;        this.ext=ext;    }    public void processDirectoryTree(File root) throws IOException {        for (File file : Directory.walk(root.getAbsolutePath(), ".*\\." + ext)) {            strategy.process(file.getCanonicalFile());        }    }    public void start(String[] args) {        try {            if (args.length == 0) {                processDirectoryTree(new File("."));            }else{                for (String arg : args) {                    File fileArg = new File(arg);                    if (fileArg.isDirectory()) {                        processDirectoryTree(fileArg);                    }else{                        if(!arg.endsWith("."+ext))                            arg+="."+ext;                        strategy.process(new File(arg).getCanonicalFile());                    }                }            }        } catch (IOException e) {            e.printStackTrace();        }    }}//改进后代码interface IStrategy{    void process(File file);}class ProcessFiles1 {    private IStrategy strategy;    private String ext;    public ProcessFiles1(IStrategy strategy, String ext) {        this.strategy=strategy;        this.ext=ext;    }    public void start(String[] paths){        for(String path:paths){            start(path);        }    }    public void start(String path) {        core(new File(path));    }    public void start(){        start(".");    }    private void core(File root){        if(root.isFile()){            strategy.process(root);            return;        }        for (File item : Directory.walk(root.getAbsolutePath(), ".*\\." + ext)) {            strategy.process(root);        }        return;    }}class ProcessFileTest {    public static void test() {        new ProcessFiles(new ProcessFiles.Strategy(){            public void process(File file) {                System.out.println(file);            }        },"java").start(new String[0]);    }    public static void test2() {        new ProcessFiles1(new IStrategy(){            public void process(File file) {                try {                    System.out.println(file.getCanonicalFile());                } catch (IOException e) {                    e.printStackTrace();                }            }        },"java").start();    }}