Java IO 目录列表器(二)

目录列表–DirFilter这个类存在的唯一原因就是将accept()方法。创建这个类的目的在于把accept()方法提供给list()使用，使list()可以回调accept()，进而决定那些文件包含在列表中。

package cn.io;
import java.io.File;
import java.io.FilenameFilter;
import java.util.Arrays;
import java.util.regex.Pattern;

public class DirList {
	public static void main(String[] args) {
		File path = new File(".");
		String [] list;
		if(args.length == 0)
			list = path.list();
		else
			list = path.list(new DirFilter(args[0]));
		Arrays.sort(list,String.CASE_INSENSITIVE_ORDER);
		for(String dirItem:list)
			System.out.println(dirItem);
	}
}
class DirFilter implements FilenameFilter{
	private Pattern pattern;
	public DirFilter(String regex){
		pattern =Pattern.compile(regex);
	}
	public boolean accept(File dir,String name){
		return pattern.matcher(name).matches();
	}
}

匿名—注意，传向filter()的参数必须未final。这在匿名内部类中是必须的，这样它才能够使用来自
该类范围之外的对象。

package cn.io;

import java.io.File;
import java.io.FilenameFilter;
import java.util.Arrays;
import java.util.regex.Pattern;

public class DIrList2 {
	public static FilenameFilter filter(final String regex){
		return new FilenameFilter(){
			private Pattern pattern = Pattern.compile(regex);
			public boolean accept(File dir,String name){
				return pattern.matcher(name).matches();
			}
		};//End of anonymous inner class(匿名内部类)
	}
	public static void main(String[] args) {
		File path = new File(".");
		String [] list;
		if(args.length == 0)
			list = path.list();
		else
			list = path.list(filter(args[0]));
		Arrays.sort(list,String.CASE_INSENSITIVE_ORDER);
		for(String dirItem:list)
			System.out.println(dirItem);
	}

}

优化–定义一个作为list()参数的匿名内部类

public class DirList3 {

	public static void main(final String[] args) {
		File path = new File(".");
		String [] list;
		if(args.length == 0)
			list =path.list();
		else
			list = path.list(new FilenameFilter() {
				private Pattern pattern = Pattern.compile(args [0]);
				public boolean accept(File dir,String name){
					return pattern.matcher(name).matches();
				}
		});
		Arrays.sort(list ,String.CASE_INSENSITIVE_ORDER);
		for(String dirItem:list)
			System.out.println(dirItem);
	}

}