[英]how do I break a while loop when asking for user input?
當用戶輸入空行而不是國家時,我需要嘗試打破 while 循環。 這是我到目前為止所做的代碼,它似乎不想結束詢問國家/地區的循環:
public void userInterface()
{
// interactive interface
Scanner input = new Scanner(System.in);
System.out.println("Enter the date:");
String date = input.nextLine();
ArrayList<String> countries = new ArrayList<String> ();
System.out.println ("Enter the list of countries (end with an empty line):");
while (input.hasNext()) {
String country = input.nextLine();
if (country.isEmpty()){
break;
}
char c = country.charAt(0);
if (Character.isUpperCase(c)==false){
System.out.println ("Type with Capital Letter!");
} else {
countries.add(country);
}
}
}
用戶輸入應如下所示:
Enter the date:
2022-02-17
Enter the list of countries (end with an empty line):
Norway
Suriname
South Namibia
您檢查hasNext()
但應該檢查hasNextLine()
。
但是,不要這樣做:
while (true) {
String country = input.nextLine();
if (country.isEmpty()){
break;
}
char c = country.charAt(0);
if (!Character.isUpperCase(c)){
System.out.println ("Type with Capital Letter!");
} else {
countries.add(country);
}
}
您還可以在 do while 循環之前設置一個空的國家/地區字符串,並在最后檢查該國家/地區是否為空:
public void userInterface()
{
// interactive interface
Scanner input = new Scanner(System.in);
System.out.println("Enter the date:");
String date = input.nextLine();
ArrayList<String> countries = new ArrayList<String> ();
System.out.println ("Enter the list of countries (end with an empty line):");
String country = "";
do
{
country = input.nextLine();
if(!country.isEmpty()) {
char c = country.charAt(0);
if (Character.isUpperCase(c) == false)
{
System.out.println("Type with Capital Letter!");
}
else
{
countries.add(country);
}
}
} while(!country.isEmpty());
}
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