java黑皮书课后习题：12.28更改文件名

import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.regex.Pattern;
import java.util.regex.Matcher;
import java.util.*;
public class test {

public static void main(String[] args) {
	for(int i = 0;i < args.length;i++) {
		File file = new File(args[i]);
		try {
			renameFile(file,"");

		}catch(Exception e) {
			System.out.println(e.getMessage());
		}
	}
	
}

public static void renameFile(File file,String rootPath) throws Exception{
	if(!file.exists())
		return;
	
	if(!file.isDirectory()) {
		rename(file,rootPath);
	}else {
		rename(file,rootPath);
		if(file.listFiles().length == 0)
			return ;
		for(File f : file.listFiles()) {
			renameFile(f,f.getParent());
		}
	}
}

public static void rename(File file,String rootPath) throws Exception{
	String fileName = file.getName();
	if(!fileName.contains("Exercise") || fileName.length() <= 10)
		return;
	String fileName1 = fileName.substring("Exercise".length(),fileName.length());
	if(Character.isDigit(fileName1.charAt(0)) && !Character.isDigit(fileName1.charAt(1))) {
		fileName1 = 0 + fileName1;
	}
	if(Character.isDigit(fileName1.charAt(fileName1.length() - 1)) && !Character.isDigit(fileName1.charAt(fileName1.length() - 2))){
		StringBuffer fileBuffer = new StringBuffer(fileName1);
		fileBuffer.insert(fileBuffer.length() - 1, '0');
		fileName1 = fileBuffer.toString();
	}
	String fileroot = file.getParent();
	fileName1 = "Exercise" + fileName1;
	File newfile = new File(fileroot +  File.separator +fileName1);
	file.renameTo(newfile);
}

}