How do I make my Java program not accept numbers as given by the user?
I would like, in a field that requires the user's name, if a number is inserted, such as a badge, do with what program reorder the name.
I have already thought of several options such as making a "alphabet of numbers", but I do not know if Java will be the best option.
One way you can use to check whether a string contains certain characters is through regular expressions, in Java you can use the String.Matches() , this method returns true if the given string parameter matches a given regex . p>
In practice it would look something like this:
public boolean checkLetters(String str)
{
return str.matches("[a-zA-Z]+");
}
Example:
public Main()
{
Scanner sc = new Scanner(System.in);
System.out.println("Digite o seu nome: ");
String nome = sc.nextLine().trim();
if (checkLetters(nome))
{
// Fazer alguma coisa aqui.
}
else
{
System.out.println("Neste campo não é permitido números. Tente Novamente.");
}
}
Demo on Ideone .
Assuming you're using console, you can do something like this:
public static String lerNome(String mensagem, Scanner scanner) {
while (true) {
System.out.println(mensagem);
String lido = scanner.nextLine().trim();
if (lido.isEmpty()) {
System.out.println("Desculpe, você não digitou nada. Tente novamente.");
continue;
}
try {
new BigDecimal(lido);
System.out.println("Desculpe, mas " + lido + " é um número. Você deveria ter digitado um nome. Tente novamente.");
} catch (NumberFormatException e) {
return lido;
}
}
}
And then you would use this method like this:
Scanner ent = new Scanner(System.in);
String nome = lerNome("Digite o nome.", ent);
This code shows the message Digite o nome. and reads a line of text read from the user. If this line of text is blank or a number, it gives an error message and does not exit the loop, prompting the user to retype. Otherwise (not blank and not number), it accepts and returns typed text.
You can create a unique method that takes as an argument the String to be checked for numbers or not. For example:
public boolean hasNumbers(final String string){
String numbers = "0123456789";
for(char a : string.toCharArray())
for(char b : numbers.toCharArray())
if(a == b) return true;
return false;
}
So you can use it in any application, be it Swing, console or web.
Scanner input = new Scanner(System.in);
if(hasNumbers(input.nextLine())){
// tem números, faz algo...
}
String input = textField.getText(); // pega o valor no jtextfield
if(hasNumbers(input)){
// tem números, faz algo...
}
Test at Ideone .
See also QMechanic73 response using regex .
Only Put That In KeyReleased Event:
char[] text = txt.getText().toCharArray();
if (txt.getText().length() > 0){
for (int i = 0; i < text.length; i++){
if (text[i] >= '0' && text[i] <= '9'){
txt.setText(txt.getText().replace(String.valueOf(text[i]), ""));
}
}
}
Since you use Netbeans it will not be difficult to add it, select the Textbox, go to events in the lower right corner and search for KeyReleased.