java例程练习（批量修改文件后缀名）

/**
 * 文件后缀名修改器
 * 说明：UI部分
 * @author Yours风之恋
 * 
 * 创建时间：2012-8-8
 *
 */
public class UserInterface {
	public static void mainMenuDisplay() {
		System.out.println("-------------------批量修改文件后缀名----------------------");
		System.out.println("  Copyright 2012              ");
		System.out.println("  @author Yours风之恋                     ");
		System.out.println("-----------------------------------------------------------\n");
	}
	
	public static void helpMenuDisplay() {
		System.out.println("-------------------系统帮助-------------------");
		System.out.println("本系统需要两个参数：");
		System.out.println("1,需要修改的文件所在文件夹目录");
		System.out.println("2,自定义的后缀名");
	}
	
	public static void waitUserInput() {
		System.out.println();
		System.out.println("系统正在等待您的输入：");
	}
}

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

public class FEA {

	public static void main(String[] args) {
		init();
		start();
	}
	
	public static void start() {
		System.out.println("请输入文件所在文件夹目录,按回车键结束。");
		String dir = getInput();
		list(dir, 0);
		System.out.println("请输入自定义的后缀名,按回车键结束。");
		String extension = getInput();
		long l1 = System.currentTimeMillis();
		change(dir, extension);
		long l2 = System.currentTimeMillis();
		System.out.println("后缀名修改成功,用时：" + (l2-l1) + "毫秒");
	}

	public static void listFiles(File f, int level, int key) {
		if (!f.isDirectory()) {
			System.out.println("目录不正确，本次服务结束 ！");
			System.exit(0);
		}
		
		String preStr = "";
		for (int i = 0; i < level; i++) {
			preStr += "    ";
		}

		File[] childs = f.listFiles();
		for (int i = 0; i < childs.length; i++) {
			System.out.println(preStr + childs[i].getName());

			if (childs[i].isDirectory() && key == 0) {
				listFiles(childs[i], level + 1, key);
			}
		}
	}

	public static void changeExtension(File f, String extension) {
		if (!f.isDirectory()) {
			System.out.println("目录不正确，本次服务结束 ！");
			System.exit(0);
		}

		File[] childs = f.listFiles();
		for (int i = 0; i < childs.length; i++) {
			if (childs[i].isFile()) {
				String parStr = childs[i].getParent();

				String filStr = childs[i].getName();
				StringBuilder sbStr = new StringBuilder(filStr);
				
				for(int k = sbStr.length() -1; k >= 0 ; k--) {
					char c = sbStr.charAt(k);
					if(c != '.') {
						sbStr.deleteCharAt(k);
					} else {
						break;
					}
				}
				sbStr.append(extension);
				File fx = new File(parStr, sbStr.toString());
				childs[i].renameTo(fx);
				
			}

			if (childs[i].isDirectory()) {
				changeExtension(childs[i], extension);
			}
		}
	}

	public static void change(String dir, String extension) {
		File f = new File(dir);
		changeExtension(f, extension);
	}

	public static void list(String dir, int key) {
		File f = new File(dir);
		listFiles(f, 0, key);
	}

	public static String getInput() {
		Scanner sc = new Scanner(System.in);
		return sc.next();
	}

	public static void init() {
		UserInterface.mainMenuDisplay();
		UserInterface.helpMenuDisplay();
		UserInterface.waitUserInput();
	}
}

另有源码和可执行文件:http://download.csdn.net/detail/haifengzhilian/4494395