Check that the string is a number between 0 and 99

Question

public class raceCar{
    private String driver;
    private String car;

    public raceCar(String driver, String car){
        this.driver = driver;
        this.car = car;
    }
}

I need to pass in two strings in the constructor, but the constructor needs to check that the string is a number between 0 and 99, If it is not, set it to "00".

[Convert int to string](http://stackoverflow.com/questions/5585779/how-to-convert-string-to-int-in-java), [basic if-then tutorial](http://docs.oracle.com/javase/tutorial/java/nutsandbolts/if.html). — rutter, Oct 21 '13 at 23:59

Bohemian · Answer 1 · 2013-10-22T00:37:57.473

3

To test, use regex:

if (str.matches("[1-9]?\\d")) {
    // it's a number between 0 and 99
}

This works by using a regular expression to check the string. The parts of the expression are:

[1-9]? a single character in the range 1 to 9, made optional by the ?
\d any digit

The regex could have been \d\d, but that would have allowed "00".

FYI, in java String.matches() only returns true if the entire String matches the pattern, so no need for ^ and $. This is unlike many other languages that return true for a partial match.

edited Oct 22 '13 at 00:37

answered Oct 22 '13 at 00:00

Bohemian

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This is a great answer, but it may be harder for the opening poster to understand without an explanation of what's going on – But I'm Not A Wrapper Class Oct 22 '13 at 00:03

score 2 · Answer 2 · edited Oct 22 '13 at 00:01

2

You could convert your string to an int using Integer.parseInt() and then use an if-statement to check if its both greater then -1 and less then 100.

edited Oct 22 '13 at 00:01

Beau Grantham

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answered Oct 21 '13 at 23:59

sirFunkenstine

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This is something simple that a beginner to Java can understand. Use try/catch with an if statement check under the try. – But I'm Not A Wrapper Class Oct 22 '13 at 00:04
Thank you! This also works, and i've learned about it in class before – user2905087 Oct 22 '13 at 00:13

score 0 · Answer 3 · answered Oct 22 '13 at 00:14

public class raceCar
{
    private String driver;
    private String car;

    public raceCar(String driver, String car)
    {
        if (Integer.parseInt(driver) < 100 && Integer.parseInt(driver) >= 0)
            this.driver = driver;
        else
            this.driver = "00";

        if (Integer.parseInt(car) < 100 && Integer.parseInt(car) >= 0)
            this.car = car;
        else
            this.car = "00";
    }

Check that the string is a number between 0 and 99

3 Answers3