Table of Contents
In this article, you will learn how to convert a string to an integer In Java. A string should be parsable in order for the operation to succeed. Otherwise, the program will throw a NumberFormatException
exception.
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Convert String to an integer using Java
In Java, we can simply use the function Integer.valueOf
to convert a string into an integer.
For example:
Integer.valueOf("33");
Will return an integer value of 33.
Examples of converting string to an integer using Java
public class Main { public static void main (String[]args) { Integer.valueOf ("10"); // returns 10 Integer.valueOf ("+10"); // returns 10 Integer.valueOf ("-10"); // returns -10 Integer.valueOf ("1 0");// NumberFormatException, cannot caintain space Integer.valueOf ("9087984321");// NumberFormatException, exeeds max integer values of 2,147,483,647 bytes Integer.valueOf ("1 @ 1");// NumberFormatException, symbols are not allowed Integer.valueOf ("");// NumberFormatException, empty string Integer.valueOf (null);// NumberFormatException, null value } }
NumberFormatException Exception in Java
as mentioned before, if a string is not parsable, the program will throw the NumberFormatException
exception.
For Example:
Integer.valueOf ("1 0"); // Space is not allowed
This code will throw the exception below since space is not allowed character in a number.
Exception in thread "main" java.lang.NumberFormatException: For input string: "1 0" at java.base/java.lang.NumberFormatException.forInputString(NumberFormatException.java:65) at java.base/java.lang.Integer.parseInt(Integer.java:652) at java.base/java.lang.Integer.valueOf(Integer.java:983) at Main.main(Main.java:14)
Example of NumberFormatException Exception in Java
Use the Try Catch
block to avoid a termination of the program when an exception occurs. The example below demonstrate how to handle the NumberFormatException
exception in your Java program.
public class Main { public static void main (String[]args) { String stringNumber = " 10"; // Contains space. Integer result; try { result = Integer.valueOf (stringNumber); System.out.println (result); } catch (NumberFormatException e) { System.err.println ("Invalid number format."); } } }
Output
Invalid number format.
Happy coding!

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