如何检查TextField是否仅包含（DOT）字符

Question

How to check if the TextField contains only (DOT) character. The TextField can contain the following below things...

.9 = > Valid
9. = > Valid
9.23 = >Valid

But if the TextField contains only (.), then the user should be thrown an error message. I cannot do a Text.startsWith() or neither Text.contains() as both may fail in other cases.

Answer 1

Use this regular expression

text.matches("\\d+|\\d*\\.\\d+|\\d+\\.\\d*")

• \\\\d+ matches only digits
• \\\\d*\\\\.\\\\d+ matches strings that start either with dot or digit and contain a dot
• \\\\d+\\\\.\\\\d* matches strings that start with digit, contain a dot and any number of digits after it

Keep in mind that numbers starting with 0 will also be accepted by this expression.

Answer 2

You can simply use

text.equals(".")

or, to take whitespaces into account,

text.trim().equals(".")

Answer 3

If you also have to check that in addition to the dot you also have a digit, you should probably write a couple of regexps.

In your case a string is valid if it matches the following patterns:

\d+       // Digits without the dot
\d*\.\d+  // Number with some digits after the dot
\d+\.\d*  // Number with some digits before the dot

Answer 4

you can just use two method

if(yourTextFieldName.getText().endsWith(".") && yourTExtFieldName.startsWith(".")) {
    //write your code here
}