What s the best way to check if a String represents an integer in Java

0 votes
I normally use the following idiom to check if a String can be converted to an integer.

public boolean isInteger( String input ) {
    try {
        Integer.parseInt( input );
        return true;
    }
    catch( Exception e ) {
        return false;
    }
}

Is it just me, or does this seem a bit hackish? What's a better way?
Apr 26, 2018 in Java by developer_1
• 3,350 points
3,897 views

2 answers to this question.

0 votes
If you are not concerned with potential overflow problems this function will perform about 20-30 times faster than using Integer.parseInt().

public static boolean isInteger(String str) {
    if (str == null) {
        return false;
    }
    int length = str.length();
    if (length == 0) {
        return false;
    }
    int i = 0;
    if (str.charAt(0) == '-') {
        if (length == 1) {
            return false;
        }
        i = 1;
    }
    for (; i < length; i++) {
        char c = str.charAt(i);
        if (c < '0' || c > '9') {
            return false;
        }
    }
    return true;
}
answered Apr 26, 2018 by Rishabh
• 3,620 points
0 votes

You can also use regular expression.

str.matches("-?\\d+");

It will give you output as:

-?     --> negative sign, could have none or one
\\d+   --> one or more digits
answered Aug 9, 2018 by Daisy
• 8,140 points

Related Questions In Java

0 votes
0 answers

What's the best way to convert a number to a string in JavaScript?

What method is the "best" for convert ...READ MORE

Nov 8, 2022 in Java by Nicholas
• 7,760 points
353 views
0 votes
2 answers

what is the best way to convert an ArrayList to a String

You could probably use the Joiner class ...READ MORE

answered Aug 19, 2019 in Java by Sirajul
• 59,230 points
1,191 views
0 votes
2 answers

What is the easiest way to iterate through the characters of a string in Java?

There are two approaches to this: for(int i ...READ MORE

answered Aug 19, 2019 in Java by Sirajul
• 59,230 points
1,782 views
0 votes
2 answers

In Java, what is the best way to determine the size of an object?

I happened to find a java class "jdk.nashorn.internal.ir.debug.ObjectSizeCalculator", ...READ MORE

answered Aug 19, 2019 in Java by Sirajul
• 59,230 points
12,899 views
0 votes
3 answers

How to check if a String is numeric in Java?

Check if a string is numeric public class ...READ MORE

answered Dec 29, 2020 in Java by Carlos
2,717 views
0 votes
3 answers

Check if a String is numeric in Java

Java 8 Lambda Expression is used: String someString ...READ MORE

answered Sep 3, 2018 in Java by Daisy
• 8,140 points
3,612 views
0 votes
1 answer

The best way to filter a Java Collection?

 this problem is solved using streams and ...READ MORE

answered May 29, 2018 in Java by Parth
• 4,640 points
789 views
0 votes
1 answer

How to pad an integer with zeros on the left in Java?

Use java.lang.String.format() method. String.format("%05d", number ...READ MORE

answered May 31, 2018 in Java by Daisy
• 8,140 points
2,215 views
0 votes
2 answers

Integer to String conversion in java

We can do this in 2 ways: String ...READ MORE

answered Jul 28, 2018 in Java by samarth295
• 2,220 points
1,056 views
0 votes
1 answer

How to divide a string in two parts

String s="yourstring"; boolean flag = true; for(int i=0;i<s.length();i++) { ...READ MORE

answered Apr 13, 2018 in Java by Rishabh
• 3,620 points
1,137 views
webinar REGISTER FOR FREE WEBINAR X
REGISTER NOW
webinar_success Thank you for registering Join Edureka Meetup community for 100+ Free Webinars each month JOIN MEETUP GROUP