How to convert String to Integer in Java

There are a couple of methods which are being followed in order to convert a number represented as a String into an integer data type. The method which is widely used to convert String to int is known as parseInt().

Integer.parseInt()

parseInt() is the static method of Integer class. Let us look at an example and understand how parseInt() works.

public class string_to_int { public static void main(String args[]) { String str = "555"; int i = Integer.parseInt(str); System.out.println(i); //Differentiate string and int data type System.out.println(str + 100); System.out.println(i + 100); } }

Output

Let us look at the output of the above example code.

String to Int using parseInt() — Fig.1- String to Integer using *parseInt()*

Here we can clearly differentiate between String data type and int data type. The second output statement, “555100” is a String which concatenates the String “555” with “100” whereas the next output statement, 655 is of the type int which adds 555 with 100.
There is another method which is used to convert String to int in Java.

Integer.valueOf()

The method parseInt() converts String to a primitive int, whereas the method valueOf() converts String to an Integer object. Let us look at an example depicting valueof() method.

public class string_to_int { public static void main(String args[]) { String str = "200"; int i = Integer.valueOf(str); System.out.println(i); } }

Output

Let us look at the output of the above example code.

String to Int using valueOf() — Fig.2- String to Int using *valueOf()*

It should be noted that valueOf() internally uses parseInt() to convert String to int.

NumberFormatException

In certain scenarios, when the String which is being converted to int does not contain a parsable integer, then the NumberFormatException is thrown.
Let us look at an example for those scenarios.

public class string_to_int { public static void main(String args[]) { String str = "200AB"; int i = Integer.valueOf(str); System.out.println(i); } }

Output

Let us look at the output of the above example code.

String to Int NumberFormatException — Fig.3- String to Int *NumberFormatException*

Here the String which is being parsed is “200AB”. It contains the characters “AB” concatenated with "200", which cannot be parsed to int. Therefore, the program throws an exception.
Now, let us look at the code which will handle this exception.

public class string_to_int { public static void main(String args[]) { String str1 = "200AB"; String str2 = "200"; try { int i = Integer.valueOf(str1); System.out.println(i); } catch (NumberFormatException e) { System.out.println("The String cannot be converted to int."); } try { System.out.println(Integer.parseInt(str2)); } catch (NumberFormatException e) { System.out.println("The String cannot be converted to int."); } } }

Output

Let us look at the output of the above example code.

The program is self explanatory how the exception case is handled using the catch clause, which is executed when the program runs into some kind of run time error.

Summary

To convert String data type to Integer data type in Java, we have a couple of methods which are being followed widely, namely, parseInt() and valueOf(). Both these methods are static method of Integer class. The method valueOf() uses the method parseInt() internally in order to convert a String to an integer data type. However, there are at times when the program throws a NumberFormatException when the String entered is not parsable in number format.

How to convert String to Integer in Java

Integer.parseInt()

Output

Integer.valueOf()

Output

NumberFormatException

Output

Output

Summary

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Author : Satyam Kumar -

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