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How can I get the int value from a string such as 423e - i.e. a string that contains a number but also maybe a letter?
Integer.parseInt() fails since the string must be entirely a number.
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To check whether a String contains only unicode letters or digits in Java, we use the isLetterOrDigit() method and charAt() method with decision-making statements. The isLetterOrDigit(char ch) method determines whether the specific character (Unicode ch) is either a letter or a digit.
Yes, that's fine. Characters are simply small integers, so of course the smaller value fits in the larger int variable, there's nothing to warn about. Many standard C functions use int to transport single characters, since they then also get the possibility to express EOF (which is not a character).
In order to check if a String has only Unicode letters in Java, we use the isDigit() and charAt() methods with decision-making statements. The isLetter(int codePoint) method determines whether the specific character (Unicode codePoint) is a letter. It returns a boolean value, either true or false.
Replace all non-digit with blank: the remaining string contains only digits.
Integer.parseInt(s.replaceAll("[\\D]", ""))
This will also remove non-digits inbetween digits, so "x1x1x" becomes 11.
If you need to confirm that the string consists of a sequence of digits (at least one) possibly followed a letter, then use this:
s.matches("[\\d]+[A-Za-z]?")
The NumberFormat class will only parse the string until it reaches a non-parseable character:
((Number)NumberFormat.getInstance().parse("123e")).intValue()
will hence return 123.
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