Thinking in Java(10)-Java IO，

Thinking in Java(10)-Java IO，

1.一个目录列表器的实现

package interfaces.classprocessor;
import java.io.*;
public class DirList {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        try{
            File path = new File("C:/Docs/Java8 API/docs/api/java/io");
            String[] list = null;
            if (args.length == 0)
                list = path.list();
            else
                list = path.list(new DirFilter(list[0]));
            for (int i = 0;i < list.length;i++)
                System.out.println(list[i]);
        }
        catch(Exception e) {
            e.printStackTrace();
        }
    }
}

class DirFilter implements FilenameFilter {
    String afn;
    DirFilter(String afn){
        this.afn = afn;
    }
    @Override
    public boolean accept(File dir, String name) {
        // TODO Auto-generated method stub
        String f = new File(name).getName();
        return f.indexOf(afn) != -1;
    }

}

这个小例子中使用了回调机制，list()回调了accept()方法。不是很理解回调的话，看完这篇文章就理解了:一个经典例子让你彻彻底底理解java回调机制.
用匿名内部类重写目录列表器:

package interfaces.classprocessor;
import java.io.*;
public class DirList2 {
    public static FilenameFilter filter(final String afn) {
        return new FilenameFilter() {
            String fn = afn;
            @Override
            public boolean accept(File dir, String name) {
                // TODO Auto-generated method stub
                String f = new File(name).getName();
                return f.indexOf(fn) != -1;
            }

        };
    }

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        try {
            File path = new File("C:/Docs/Java8 API/docs/api/java/io");
            String[] list;
            if (args.length == 0)
                list = path.list();
            else
                list = path.list(filter(args[0]));
            for (int i = 0;i < list.length;i++)
                System.out.println(list[i]);
        }
        catch(Exception e)
        {
            e.printStackTrace();
        }
    }
}

甚至可以把匿名内部类写成list的一个参数:

package interfaces.classprocessor;
import java.io.*;
public class DirList3 {

    public static void main(final String[] args) {
        // TODO Auto-generated method stub
        try {
            File path = new File("C:/Docs/Java8 API/docs/api/java/io");
            String[] list;
            if (args.length == 0)
                list = path.list();
            else
                list = path.list(
                        new FilenameFilter() {
                            public boolean accept(File dir,String name)
                            {
                                String f = new File(name).getName();
                                return f.indexOf(args[0]) != -1;

                            }
                        }
                        );
            for(int i = 0;i < list.length;i++)
                System.out.println(list[i]);
        }
        catch (Exception e)
        {
            e.printStackTrace();
        }

    }

}