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();
}
}