public static int inputChoose(String m) {//返回整形
  Scanner sc = new Scanner(System.in);
  System.out.print(m + "：");
  return sc.nextInt();
 }
//---------------------------------------------------------------------------
 public static String inputAccount(){//输入账号
  Console c = System.console();
  return c.readLine("请输入账号：");
 }

//---------------------------------------------------------------------------
 public static void  sleep(int i ){//系统等待
  try {
   Thread.sleep(i*1000);
  } catch (InterruptedException e) {
   e.printStackTrace();
   } 
 }

//---------------------------------------------------------------------------

public static void  writeUser(User u){//把对象放入Map并写入文件
  HashMap<String, User> map = new HashMap<String,User>();
  try {
   ObjectInputStream ois = new ObjectInputStream(new FileInputStream("bank/user.dat"));
   try {
    map = (HashMap<String,User>)ois.readObject();
    map.put(u.getCd(), u);
    ois.close();
   } catch (ClassNotFoundException e) {
    e.printStackTrace();
   }
  } catch (FileNotFoundException e1) {
   e1.printStackTrace();
  } catch (IOException e1) {
   e1.printStackTrace();
  }
  try {
   ObjectOutputStream oos =new ObjectOutputStream(new FileOutputStream("bank/user.dat"));
   oos.writeObject(map);
   oos.close();
  } catch (FileNotFoundException e) {
   e.printStackTrace();
  } catch (IOException e) {
   e.printStackTrace();
  }
 }

//---------------------------------------------------------------------------
 public static String inputPassword(String m){//console输入密码

  Console c = System.console();
  return new String(c.readPassword(m+"："));
 }
//---------------------------------------------------------------------------

 public static String input(){//输入 String
  Scanner sc =new Scanner(System.in);
  return sc.next();
 }
//--------------------------------------------------------------------------- 
 public static String inputPassword(){//console输入密码//控制台输入！eclipse会报异常

  Console c = System.console();
  return new String(c.readPassword("请输入密码："));
 }
//---------------------------------------------------------------------------
 public static int inputChoose(){//返回值int类型
  Scanner sc = new Scanner(System.in);
  System.out.print("请选择：");
  return sc.nextInt();
 }
//---------------------------------------------------------------------------
 public static String md(String md,String pass){//密码加密 MD5方法
  MessageDigest m;
  String passok = "";
  try {
   m = MessageDigest.getInstance(md);
   m.update(pass.getBytes());
   for (byte b : m.digest()) {
    passok += String.format("%x", b);
   }
  } catch (NoSuchAlgorithmException e) {
   e.printStackTrace();
  }
  return passok;
 }
//---------------------------------------------------------------------------
public  static  boolean  authenticationKey(String cd){// 用户密码验证
     System.out.println("请输入密码");
     String newKey = md("MD5",input());
     String oldKey = outUser(cd).getKey();
     if(newKey.equals(oldKey)){
      return true;
     }else{
      return false;
     }
}
//-------------------------------------------------------
@SuppressWarnings("unchecked")
public static void  removeUser(User user){//删除对象
 HashMap<String, User> map = new HashMap<String,User>();
 try {
  ObjectInputStream ois = new ObjectInputStream(new FileInputStream("bank/user.dat"));
  try {
   map = (HashMap<String,User>)ois.readObject();
   map.remove(user.getCd());
   ois.close();
  } catch (ClassNotFoundException e) {
   e.printStackTrace();
  }
 } catch (FileNotFoundException e1) {
  e1.printStackTrace();
 } catch (IOException e1) {
  e1.printStackTrace();
 }
 try {
  ObjectOutputStream oos =new ObjectOutputStream(new FileOutputStream("bank/user.dat"));
  oos.writeObject(map);
  oos.close();
 } catch (FileNotFoundException e) {
  e.printStackTrace();
 } catch (IOException e) {
  e.printStackTrace();
 }
}
//-------------------------------------------------------------------------------------

Java 常用方法搜集 欢迎补充