我怎样才能让用户能够通过使用扫描仪功能在键盘上无限输入内容？
How can I allow the user to be able to input something by typing in the keyboard infinitely using the Scanner feature?
在我的代码中，我能够使用扫描仪功能来提示用户键入一段文本，但是，我只能做到这一点，因此用户只能键入一次。要再次输入，我将不得不关闭终端，然后再次打开它，我怎样才能做到这样我就可以无限地输入，这样我就不必每次都关闭它并重新打开它来再次输入？
对于上下文，这是我的代码，它是关于一个显示某些数据的售票机，比如人名、价格、总余额等。目前我正在做这些地方。这意味着我希望用户键入英格兰的任何城市，然后会出现一个价格。但正如我所说，用户一次只能刺耳地输入一件事，而他们应该可以无限制地输入。
import java.util.Scanner;
import java.lang.String;
public class TicketMachine
{
private int price;
private int balance;
private int total;
/**
* Create a machine that issues tickets of the given price.
*/
public TicketMachine(int cost)
{
price = cost;
balance = 0;
total = 0;
}
/**
* @Return The price of a ticket.
*/
public int getPrice()
{
return price;
}
/**
* Return The amount of money already inserted for the
* next ticket.
*/
public int getBalance()
{
return balance;
}
/**
* Receive an amount of money from a customer.
* Check that the amount is sensible.
*/
public void insertMoney(int amount)
{
if(amount > 0) {
balance = balance + amount;
}
else {
System.out.println("Use a positive amount rather than: " +
amount);
}
}
/**
* Print a ticket if enough money has been inserted, and
* reduce the current balance by the ticket price. Print
* an error message if more money is required.
*/
public void printTicket()
{
if(balance >= price) {
// Simulate the printing of a ticket.
System.out.println("HERE IS YOUR TICKET");
System.out.println("# Ticket");
System.out.println("# " + price + " cents.");
System.out.println("You have" + balance + "left");
// Update the total collected with the price.
total = total + price;
// Reduce the balance by the price.
balance = balance - price;
}
else {
System.out.println("You must insert at least: " +
(price - balance) + " more cents.");
}
}
/**
* Return the money in the balance.
* The balance is cleared.
*/
public int refundBalance()
{
int amountToRefund;
amountToRefund = balance;
balance = 0;
return amountToRefund;
}
public static void main(String [] args)
{
Scanner myScanner = new Scanner(System.in);
String answer = myScanner.nextLine();
if( answer.equals("London") )
{
System.out.println("£15");
}
if( answer.equals("Manchester") )
{
System.out.println("£20");
}
if( answer.equals("Brighton") )
{
System.out.println("£25");
}
if( answer.equals("Cornwall") )
{
System.out.println("£30");
}
if( answer.equals("Crystal Palace") )
{
System.out.println("£35");
}
if( answer.equals("Chealsea") )
{
System.out.println("£40");
}
if( answer.equals("Birmingham") )
{
System.out.println("£45");
}
if( answer.equals("Liverpool") )
{
System.out.println("£50");
}
if( answer.equals("Bristol") )
{
System.out.println("£55");
}
if( answer.equals("Leister") )
{
System.out.println("£60");
}
if( answer.equals("Newcastle") )
{
System.out.println("£65");
}
if( answer.equals("Cambridge") )
{
System.out.println("£70");
}
if( answer.equals("Bradford") )
{
System.out.println("£75");
}
if( answer.equals("Leeds") )
{
System.out.println("£80");
}
if( answer.equals("Oxford") )
{
System.out.println("£85");
}
if( answer.equals("Nottingham") )
{
System.out.println("£90");
}
if( answer.equals("Peterborough") )
{
System.out.println("£95");
}
if( answer.equals("Sheffield") )
{
System.out.println("£100");
}
}
}
使用 while true 或无限循环不是好的做法。您可以使用 do-while 并检查标志（例如“退出”）来关闭程序，例如
import java.util.Scanner;
import java.lang.String;
public class TicketMachine {
private int price;
private int balance;
private int total;
/**
* Create a machine that issues tickets of the given price.
*/
public TicketMachine(int cost) {
price = cost;
balance = 0;
total = 0;
}
/**
* @Return The price of a ticket.
*/
public int getPrice() {
return price;
}
/**
* Return The amount of money already inserted for the next ticket.
*/
public int getBalance() {
return balance;
}
/**
* Receive an amount of money from a customer. Check that the amount is sensible.
*/
public void insertMoney(int amount) {
if (amount > 0) {
balance = balance + amount;
} else {
System.out.println("Use a positive amount rather than: "
+ amount);
}
}
/**
* Print a ticket if enough money has been inserted, and reduce the current balance by the
* ticket price. Print an error message if more money is required.
*/
public void printTicket() {
if (balance >= price) {
// Simulate the printing of a ticket.
System.out.println("HERE IS YOUR TICKET");
System.out.println("# Ticket");
System.out.println("# " + price + " cents.");
System.out.println("You have" + balance + "left");
// Update the total collected with the price.
total = total + price;
// Reduce the balance by the price.
balance = balance - price;
} else {
System.out.println("You must insert at least: "
+ (price - balance) + " more cents.");
}
}
/**
* Return the money in the balance. The balance is cleared.
*/
public int refundBalance() {
int amountToRefund;
amountToRefund = balance;
balance = 0;
return amountToRefund;
}
public static void main(String[] args) {
Scanner myScanner = new Scanner(System.in);
String answer = "";
do {
System.out.println("Enter your city, please:");
answer = myScanner.nextLine();
if (answer.equals("London")) {
System.out.println("£15");
}
else if (answer.equals("Manchester")) {
System.out.println("£20");
}
else if (answer.equals("Brighton")) {
System.out.println("£25");
}
else if (answer.equals("Cornwall")) {
System.out.println("£30");
}
else if (answer.equals("Crystal Palace")) {
System.out.println("£35");
}
else if (answer.equals("Chealsea")) {
System.out.println("£40");
}
else if (answer.equals("Birmingham")) {
System.out.println("£45");
}
else if (answer.equals("Liverpool")) {
System.out.println("£50");
}
else if (answer.equals("Bristol")) {
System.out.println("£55");
}
else if (answer.equals("Leister")) {
System.out.println("£60");
}
else if (answer.equals("Newcastle")) {
System.out.println("£65");
}
else if (answer.equals("Cambridge")) {
System.out.println("£70");
}
else if (answer.equals("Bradford")) {
System.out.println("£75");
}
else if (answer.equals("Leeds")) {
System.out.println("£80");
}
else if (answer.equals("Oxford")) {
System.out.println("£85");
}
else if (answer.equals("Nottingham")) {
System.out.println("£90");
}
else if (answer.equals("Peterborough")) {
System.out.println("£95");
}
else if (answer.equals("Sheffield")) {
System.out.println("£100");
}else {
System.out.println("ERROR: INVALID INPUT");
}
} while (answer != "exit");
}
}
PS 使用 switch case 而不是 if(){} 例如
import java.util.Scanner;
import java.lang.String;
public class TicketMachine {
private int price;
private int balance;
private int total;
/**
* Create a machine that issues tickets of the given price.
*/
public TicketMachine(int cost) {
price = cost;
balance = 0;
total = 0;
}
/**
* @Return The price of a ticket.
*/
public int getPrice() {
return price;
}
/**
* Return The amount of money already inserted for the next ticket.
*/
public int getBalance() {
return balance;
}
/**
* Receive an amount of money from a customer. Check that the amount is sensible.
*/
public void insertMoney(int amount) {
if (amount > 0) {
balance = balance + amount;
} else {
System.out.println("Use a positive amount rather than: "
+ amount);
}
}
/**
* Print a ticket if enough money has been inserted, and reduce the current balance by the
* ticket price. Print an error message if more money is required.
*/
public void printTicket() {
if (balance >= price) {
// Simulate the printing of a ticket.
System.out.println("HERE IS YOUR TICKET");
System.out.println("# Ticket");
System.out.println("# " + price + " cents.");
System.out.println("You have" + balance + "left");
// Update the total collected with the price.
total = total + price;
// Reduce the balance by the price.
balance = balance - price;
} else {
System.out.println("You must insert at least: "
+ (price - balance) + " more cents.");
}
}
/**
* Return the money in the balance. The balance is cleared.
*/
public int refundBalance() {
int amountToRefund;
amountToRefund = balance;
balance = 0;
return amountToRefund;
}
public static void main(String[] args) {
Scanner myScanner = new Scanner(System.in);
String answer = "";
do {
System.out.println("Enter your city, please:");
answer = myScanner.nextLine();
switch (answer) {
case "London":
System.out.println("£15");
break;
case "Manchester":
System.out.println("£20");
break;
case "Brighton":
System.out.println("£25");
break;
case "Cornwall":
System.out.println("£30");
break;
case "Crystal Palace":
System.out.println("£35");
break;
case "Chealsea":
System.out.println("£40");
break;
case "Birmingham":
System.out.println("£45");
break;
case "Liverpool":
System.out.println("£50");
break;
case "Bristol":
System.out.println("£55");
break;
case "Leister":
System.out.println("£20");
break;
case "Newcastle":
System.out.println("£65");
break;
case "Cambridge":
System.out.println("£70");
break;
case "Bradford":
System.out.println("£75");
break;
case "Leeds":
System.out.println("£80");
break;
case "Oxford":
System.out.println("£85");
break;
case "Nottingham":
System.out.println("£90");
break;
case "Peterborough":
System.out.println("£95");
break;
case "Sheffield":
System.out.println("£100");
break;
default:
System.out.println("ERROR: INVALID INPUT");
break;
}
} while (answer != "exit");
}
}
在我的代码中，我能够使用扫描仪功能来提示用户键入一段文本，但是，我只能做到这一点，因此用户只能键入一次。要再次输入，我将不得不关闭终端，然后再次打开它，我怎样才能做到这样我就可以无限地输入，这样我就不必每次都关闭它并重新打开它来再次输入？ 对于上下文，这是我的代码，它是关于一个显示某些数据的售票机，比如人名、价格、总余额等。目前我正在做这些地方。这意味着我希望用户键入英格兰的任何城市，然后会出现一个价格。但正如我所说，用户一次只能刺耳地输入一件事，而他们应该可以无限制地输入。
import java.util.Scanner;
import java.lang.String;
public class TicketMachine
{
private int price;
private int balance;
private int total;
/**
* Create a machine that issues tickets of the given price.
*/
public TicketMachine(int cost)
{
price = cost;
balance = 0;
total = 0;
}
/**
* @Return The price of a ticket.
*/
public int getPrice()
{
return price;
}
/**
* Return The amount of money already inserted for the
* next ticket.
*/
public int getBalance()
{
return balance;
}
/**
* Receive an amount of money from a customer.
* Check that the amount is sensible.
*/
public void insertMoney(int amount)
{
if(amount > 0) {
balance = balance + amount;
}
else {
System.out.println("Use a positive amount rather than: " +
amount);
}
}
/**
* Print a ticket if enough money has been inserted, and
* reduce the current balance by the ticket price. Print
* an error message if more money is required.
*/
public void printTicket()
{
if(balance >= price) {
// Simulate the printing of a ticket.
System.out.println("HERE IS YOUR TICKET");
System.out.println("# Ticket");
System.out.println("# " + price + " cents.");
System.out.println("You have" + balance + "left");
// Update the total collected with the price.
total = total + price;
// Reduce the balance by the price.
balance = balance - price;
}
else {
System.out.println("You must insert at least: " +
(price - balance) + " more cents.");
}
}
/**
* Return the money in the balance.
* The balance is cleared.
*/
public int refundBalance()
{
int amountToRefund;
amountToRefund = balance;
balance = 0;
return amountToRefund;
}
public static void main(String [] args)
{
Scanner myScanner = new Scanner(System.in);
String answer = myScanner.nextLine();
if( answer.equals("London") )
{
System.out.println("£15");
}
if( answer.equals("Manchester") )
{
System.out.println("£20");
}
if( answer.equals("Brighton") )
{
System.out.println("£25");
}
if( answer.equals("Cornwall") )
{
System.out.println("£30");
}
if( answer.equals("Crystal Palace") )
{
System.out.println("£35");
}
if( answer.equals("Chealsea") )
{
System.out.println("£40");
}
if( answer.equals("Birmingham") )
{
System.out.println("£45");
}
if( answer.equals("Liverpool") )
{
System.out.println("£50");
}
if( answer.equals("Bristol") )
{
System.out.println("£55");
}
if( answer.equals("Leister") )
{
System.out.println("£60");
}
if( answer.equals("Newcastle") )
{
System.out.println("£65");
}
if( answer.equals("Cambridge") )
{
System.out.println("£70");
}
if( answer.equals("Bradford") )
{
System.out.println("£75");
}
if( answer.equals("Leeds") )
{
System.out.println("£80");
}
if( answer.equals("Oxford") )
{
System.out.println("£85");
}
if( answer.equals("Nottingham") )
{
System.out.println("£90");
}
if( answer.equals("Peterborough") )
{
System.out.println("£95");
}
if( answer.equals("Sheffield") )
{
System.out.println("£100");
}
}
}
使用 while true 或无限循环不是好的做法。您可以使用 do-while 并检查标志（例如“退出”）来关闭程序，例如
import java.util.Scanner;
import java.lang.String;
public class TicketMachine {
private int price;
private int balance;
private int total;
/**
* Create a machine that issues tickets of the given price.
*/
public TicketMachine(int cost) {
price = cost;
balance = 0;
total = 0;
}
/**
* @Return The price of a ticket.
*/
public int getPrice() {
return price;
}
/**
* Return The amount of money already inserted for the next ticket.
*/
public int getBalance() {
return balance;
}
/**
* Receive an amount of money from a customer. Check that the amount is sensible.
*/
public void insertMoney(int amount) {
if (amount > 0) {
balance = balance + amount;
} else {
System.out.println("Use a positive amount rather than: "
+ amount);
}
}
/**
* Print a ticket if enough money has been inserted, and reduce the current balance by the
* ticket price. Print an error message if more money is required.
*/
public void printTicket() {
if (balance >= price) {
// Simulate the printing of a ticket.
System.out.println("HERE IS YOUR TICKET");
System.out.println("# Ticket");
System.out.println("# " + price + " cents.");
System.out.println("You have" + balance + "left");
// Update the total collected with the price.
total = total + price;
// Reduce the balance by the price.
balance = balance - price;
} else {
System.out.println("You must insert at least: "
+ (price - balance) + " more cents.");
}
}
/**
* Return the money in the balance. The balance is cleared.
*/
public int refundBalance() {
int amountToRefund;
amountToRefund = balance;
balance = 0;
return amountToRefund;
}
public static void main(String[] args) {
Scanner myScanner = new Scanner(System.in);
String answer = "";
do {
System.out.println("Enter your city, please:");
answer = myScanner.nextLine();
if (answer.equals("London")) {
System.out.println("£15");
}
else if (answer.equals("Manchester")) {
System.out.println("£20");
}
else if (answer.equals("Brighton")) {
System.out.println("£25");
}
else if (answer.equals("Cornwall")) {
System.out.println("£30");
}
else if (answer.equals("Crystal Palace")) {
System.out.println("£35");
}
else if (answer.equals("Chealsea")) {
System.out.println("£40");
}
else if (answer.equals("Birmingham")) {
System.out.println("£45");
}
else if (answer.equals("Liverpool")) {
System.out.println("£50");
}
else if (answer.equals("Bristol")) {
System.out.println("£55");
}
else if (answer.equals("Leister")) {
System.out.println("£60");
}
else if (answer.equals("Newcastle")) {
System.out.println("£65");
}
else if (answer.equals("Cambridge")) {
System.out.println("£70");
}
else if (answer.equals("Bradford")) {
System.out.println("£75");
}
else if (answer.equals("Leeds")) {
System.out.println("£80");
}
else if (answer.equals("Oxford")) {
System.out.println("£85");
}
else if (answer.equals("Nottingham")) {
System.out.println("£90");
}
else if (answer.equals("Peterborough")) {
System.out.println("£95");
}
else if (answer.equals("Sheffield")) {
System.out.println("£100");
}else {
System.out.println("ERROR: INVALID INPUT");
}
} while (answer != "exit");
}
}
PS 使用 switch case 而不是 if(){} 例如
import java.util.Scanner;
import java.lang.String;
public class TicketMachine {
private int price;
private int balance;
private int total;
/**
* Create a machine that issues tickets of the given price.
*/
public TicketMachine(int cost) {
price = cost;
balance = 0;
total = 0;
}
/**
* @Return The price of a ticket.
*/
public int getPrice() {
return price;
}
/**
* Return The amount of money already inserted for the next ticket.
*/
public int getBalance() {
return balance;
}
/**
* Receive an amount of money from a customer. Check that the amount is sensible.
*/
public void insertMoney(int amount) {
if (amount > 0) {
balance = balance + amount;
} else {
System.out.println("Use a positive amount rather than: "
+ amount);
}
}
/**
* Print a ticket if enough money has been inserted, and reduce the current balance by the
* ticket price. Print an error message if more money is required.
*/
public void printTicket() {
if (balance >= price) {
// Simulate the printing of a ticket.
System.out.println("HERE IS YOUR TICKET");
System.out.println("# Ticket");
System.out.println("# " + price + " cents.");
System.out.println("You have" + balance + "left");
// Update the total collected with the price.
total = total + price;
// Reduce the balance by the price.
balance = balance - price;
} else {
System.out.println("You must insert at least: "
+ (price - balance) + " more cents.");
}
}
/**
* Return the money in the balance. The balance is cleared.
*/
public int refundBalance() {
int amountToRefund;
amountToRefund = balance;
balance = 0;
return amountToRefund;
}
public static void main(String[] args) {
Scanner myScanner = new Scanner(System.in);
String answer = "";
do {
System.out.println("Enter your city, please:");
answer = myScanner.nextLine();
switch (answer) {
case "London":
System.out.println("£15");
break;
case "Manchester":
System.out.println("£20");
break;
case "Brighton":
System.out.println("£25");
break;
case "Cornwall":
System.out.println("£30");
break;
case "Crystal Palace":
System.out.println("£35");
break;
case "Chealsea":
System.out.println("£40");
break;
case "Birmingham":
System.out.println("£45");
break;
case "Liverpool":
System.out.println("£50");
break;
case "Bristol":
System.out.println("£55");
break;
case "Leister":
System.out.println("£20");
break;
case "Newcastle":
System.out.println("£65");
break;
case "Cambridge":
System.out.println("£70");
break;
case "Bradford":
System.out.println("£75");
break;
case "Leeds":
System.out.println("£80");
break;
case "Oxford":
System.out.println("£85");
break;
case "Nottingham":
System.out.println("£90");
break;
case "Peterborough":
System.out.println("£95");
break;
case "Sheffield":
System.out.println("£100");
break;
default:
System.out.println("ERROR: INVALID INPUT");
break;
}
} while (answer != "exit");
}
}