Java 简单小程序 急！！！

Question

利用I/O类库，编写一个dir命令，要求：不输入命令行参数显示当前文件夹的

所有文件，输入命令行参数则显示当前文件夹中的制定文件类型。如：输入java

显示所有扩展名为。java的文件。

Answer 1

import java.io.File;
import java.io.FilenameFilter;
import java.util.Scanner;

public class IoFilter {

private static Scanner san = new Scanner(System.in);

public static File[] doFilter(File dist, String tail) {
FilenameFilter filter = new JavaFileFilter(tail);
File[] fs = dist.listFiles(filter);
return fs;
}

public IoFilter() {
}

public static void list(File [] fs) {
if(fs == null) {
return;
}
for(File f: fs) {
System.out.println(f.getName());
}
}

public static void main(String[] args) {
String path = ".";
System.out.print("Input dist path: ");
path = san.nextLine();
File dist = new File(path);
System.out.print("filter(input dir *): ");
String input = san.nextLine();
input = input.trim();
if(!input.matches("dir.*")) {
System.err.println("Error Command!");
System.exit(-1);
return;
} else if(input.equals("dir")){
IoFilter.list(IoFilter.doFilter(dist, null));
return;
} else {
String tail = null;
tail = input.replaceFirst("dir\\s", "");
IoFilter.list(IoFilter.doFilter(dist, tail));
return;
}

}

}

class JavaFileFilter implements FilenameFilter {

private String tail = ".*";
private String filter = ".*\\.";

public JavaFileFilter(String tail) {
this.tail = tail;
}

public boolean accept(File dir, String name) {
if (this.tail == null) {
this.filter = ".*";
} else {
this.filter = ".*\\." + this.tail;
}
return name.matches(this.filter);
}

}

Answer 2

import java.io.File;
import java.io.FileFilter;
import java.util.Date;
public class Dir{
public static void main(final String[] args){
File[] subItems;
if(args.length==0){
subItems=new File(".").listFiles();
}
else{
subItems=new File(".").listFiles(new FileFilter(){
public boolean accept(File f){
return f.getName().toLowerCase().endsWith("."+args[0].toLowerCase());
}
});
}
for(int i=0;i<subItems.length;i++){
System.out.println(String.format("%1$-28s\t%2$12s\t%3$s",subItems[i].getName(),subItems[i].isDirectory()?"<DIR>":String.valueOf(subItems[i].length()),new Date(subItems[i].lastModified()).toLocaleString()));
}
}
}