在我的if语句中，如何使用，检查和比较“ enter”键作为用户的输入。 使用Java

Question

我必须：更新帐户信息：该程序应首先要求管理员输入要更新的帐户号：输入帐户号：15然后，应显示一个菜单，其中显示管理员所有的旧信息，然后执行以下步骤：分步查询以更改特定字段。 如果他将字段留空，则传播旧信息，即先前的信息保持不变。

问题：将字段保留为空白意味着按下回车键时。 我应该如何实现呢？ 我尝试使用char'10'/'13'以及'\\ n'，但是它们不能与不同类型进行比较，例如string到char以及int到char。

Heres my code:
import java.util.*;
class Customers
{

    private String name;
    private int accountno;
    private String status;
    private String type;
    private int currbal;
    private String Login;
    private int Pin;

    public Customers()
    {

        this.name   = " ";
        this.accountno = accountno;
        this.currbal = currbal; 
    }
    public Customers( String name1, int A, int Bal)
    {
        name = name1;
        accountno = A;
        currbal = Bal;      
    }
    public Customers ( String name1,int accountno1, String status1, String type1, int curr, String Login1, int Pin1)
    {   
        name = name1;
        accountno = accountno1;
        status = status1;
        type = type1;
        currbal = curr;
        Login = Login1;
        Pin = Pin1;
    }
    public String getHolderName()
    {
        return name;
    }
    public int getaccountno()
    {
        return accountno;
    }
    public String getStatus()
    {
        return status;
    }
    public String getType()
    {
        return type;
    }
    public int getCurrentBalance()
    {
        return currbal;
    }
    public String getLogin()
    {
        return Login;
    }
    public int getPin()
    {
        return Pin;
    }

    public void setName( String N)
    {
        name = N;
    }
    public void setAccountno(int account )
    {   
        accountno = account;
    }
    public void setStatus( String S)
    {
        status = S;
    }
    public void setType( String T)
    {
        type = T;
    }
    public void setCurrentBalance(int Bal )
    {
        currbal = Bal;
    }
    public void setLogin( String Log)
    {
        Login = log;
    }
    public void setPin( int Pinn )
    {
        Pin = Pinn;
    }
}

class ATMmain
{
    public static void main( String [] args)
    {   
        Customers [] Carray = new Customers [100];
        int count = 0;
        System.out.println ("Begin session (Y/N)? ");
        char ch = 'Y';
        Scanner S = new Scanner(System.in);
        ch = S.next().charAt(0);


        while ( ch == 'Y' || ch == 'y' )
        {
        System.out.println(" 1----Create New Account.");
        System.out.println("2----Delete Existing Account");
        System.out.println("3----Update Account Information. ");
        System.out.println(" 4----Search for Account.");
        System.out.println(" 5----View Reports");
        System.out.println(" 6----Exit");

        //Scanner S = new Scanner(System.in);
        int input = S.nextInt();

        if ( input == 1)
        {

        //Customers [] C1 = new Customers[1];
        //Customers [] C2 = new Customers[1];
        System.out.println(createNewAccount(count, Carray));
        count++;


        }
        if (input == 2)
        {
            System.out.println(DeleteExistingAcc(count, Carray));
            count--;

        }
        System.out.println("Do you wish to do some action" );
        ch = S.next().charAt(0);
        if (ch != 'Y' || ch != 'y' )
        {
            System.out.println ("Thank you for your time");
        }
        }
    }

    public static int createNewAccount( int count, Customers [] Carray)
    {
        //Customers [] Carray = new Customers[10];
        System.out.println("Enter account information");
        Scanner S = new Scanner (System.in); 
        System.out.println("Login:");
        String log = S.next();
        System.out.println("Pin Code:");
        int Pin = S.nextInt();
        System.out.println("Holder's name: ");
        String holderN = S.next();
        System.out.println("Type:" );
        String type = S.next();
        if (!type.equals("Savings") && !type.equals("Current"))
        {
            System.out.println("error type! please Re-enter");
            System.out.println("Type:" );
            type = S.next();
        }
        System.out.println("Starting Balance:");
        int SBal = S.nextInt();
        System.out.println("Status:");
        String Stat = S.next();
        Customers ACC = new Customers(holderN, count,Stat, type,SBal,log, Pin );
        Carray[count] = ACC;

        System.out.println("Account Successfully created!");
        System.out.println("account number is" +count);
        //count++;
        return 1;
    }

    public static int DeleteExistingAcc(int count, Customers [] Carray )
    {
        System.out.println ("Enter Account Number: ");
        Scanner S = new Scanner(System.in);
        int acc = S.nextInt();

        System.out.println("Are you sure you want to delete this Account:" +acc);
        String x = Carray[acc].getHolderName();
        System.out.println("You wish to delete the account held by: "  + x);
        System.out.println("If this information is correct, please re-enter account number: " );
        acc = S.nextInt();
        int accnew = acc + 1;
        Carray[acc] = Carray[accnew];
        System.out.println ("Account successfully deleted");

        //Carray.splice(acc,1, 0);
        return 0;

    }
    public static void display( int acc, Customer [] arr)
    {
        arr[acc].getHolderName();
        arr[acc].getLogin();
        arr[acc].getCurrentBalance();
        arr[acc].getPin();
        arr[acc].getStatus();
        arr[acc].getType();
        arr[acc].getaccountno();
    }


    public static int UpdateAccountInfo( Customers [] Carray)
    {
        System.out.println("Enter Account Number:");
        Scanner S = new Scanner(System.in);
        int acc = S.nextInt();

        display( acc, Carray);
        char ent = '/n';
        int ent1 = '/n';

        Carray[acc].getHolderName();
        String Str = S.next();
        if ( Str != '\n')                 //See here
        {
            Carray[acc].setName( Str);
        }
        Carray[acc].getaccountno();
        int account = S.nextInt();
        if( account != '10')                 //here
        {
            Carray[acc].setAccountno(account);
        }
        Carray[acc].getType();
        String type1 = S.next();
        if ( type1 != '/n' )                  //here
        {
            Carray[acc].setType( type1);
        }

        Carray[acc].getCurrentBalance();
        int bal = S.nextInt();
        if (bal != '13')              //here
        {
            Carray[acc].setCurrentBalance( bal);
        }
        Carray[acc].getStatus();
        String stat = S.next();
        if ( stat != '13')                   //here
        {
            Carray[acc].setStatus( stat);
        }

        System.out.println("Your account has been successfully updated");
    }

    }

Answer 1

您可以将S.next()替换为S.nextLine() ，并使用以下命令检测空行（ENTER键）：

String str = S.nextLine();
if (str.equals("") {
   // empty line
}

Answer 2

我在您的代码中看到的是，在UpdateAccountInfo（）方法下，您已将String对象和int数据与char文字进行了比较。

在这里，您已将String与char进行了比较。 因此，该表达式将结果为false。

    Carray[acc].getHolderName();
    String Str = S.next();
    if ( Str != '\n')                 //See here
    {
        Carray[acc].setName( Str);
    }

在这里，int对抗char。

    Carray[acc].getaccountno();
    int account = S.nextInt();
    if( account != '10')                 //here
    {
        Carray[acc].setAccountno(account);
    }

在这里，再次是针对char的String。

    Carray[acc].getType();
    String type1 = S.next();
    if ( type1 != '/n' )                  //here
    {
        Carray[acc].setType( type1);
    }

在这里，int对抗char。

    Carray[acc].getCurrentBalance();
    int bal = S.nextInt();
    if (bal != '13')              //here
    {
        Carray[acc].setCurrentBalance( bal);
    }

在这里，再次是针对char的String。

    Carray[acc].getStatus();
    String stat = S.next();
    if ( stat != '13')                   //here
    {
        Carray[acc].setStatus( stat);
    }

尝试以与获取“是/否”和菜单选项选择相同的方式进行数据比较。

好了，更好的选择是读取整行并检查其是否为空（长度为零）。

Scanner S = new Scanner(System.in);
String input = S.nextLine();
if (input != null || input.trim().length() > 0) {
    //do the update task
}
//otherwise you need not update the value