Introduction
In Java, converting a string to an integer is a common task, especially when handling user inputs or processing data from external sources. However, this conversion can be tricky if the string is not properly formatted or if the input contains non-numeric characters. In this blog, we will explore different methods to convert a string to an integer in Java.
Also Read About, Multithreading in java, and Duck Number in Java.
How to Convert String to Integer in Java?
In Java, converting a String to an int is a common requirement when working with user input, data parsing, or file handling. For instance, when you receive numerical data as a String (e.g., from a text field in a form or a configuration file), you need to convert it to an int for mathematical operations or logical comparisons. This conversion is essential to ensure that your program can process numerical data correctly and efficiently.
In Java, two primary methods exist for converting a string to an integer. Here’s a detailed explanation of both methods with examples:
1. Using Integer.parseInt() Method in Java
The first function that we use to convert java string to int is Integer.parseInt(). The string is returned as an int primitive type when we use this. Let's see an example code that will convert java string to int.
Syntax of parseInt
int number = Integer.parseInt(String s);Parameters
- s: The String to be parsed into an integer.
Return Type
- int: The method returns an integer representation of the String. If the string cannot be parsed as an integer, a NumberFormatException is thrown.
We can see that compiler is giving is error. You can try it on online java compiler.
Cases of parseInt() Method
The parseInt() method in Java is used to convert a String into an integer. This method is commonly used when parsing numbers from user input, configuration files, or other data sources that provide numeric values as strings. The method can handle both positive and negative numbers, and it also allows for specifying a radix (e.g., binary, octal, decimal, hexadecimal) when parsing the string.
Number Format Exceptions of parseInt() Method
A NumberFormatException occurs when the parseInt() method is unable to convert the provided String into an integer due to invalid format or characters.
Example:
public class ParseIntExample {
public static void main(String[] args) {
try {
int number = Integer.parseInt("123abc");
} catch (NumberFormatException e) {
System.out.println("NumberFormatException: " + e.getMessage());
}
}
}
Explanation:
In this example, the string "123abc" contains non-numeric characters (abc), causing the parseInt() method to throw a NumberFormatException. The exception indicates that the string cannot be parsed as an integer.
2. Using Integer.valueOf() Method
Another approach to converting a String to an integer in Java is by using the valueOf() method. This method also belongs to the Integer class and works similarly to parseInt(). However, it returns an Integer object instead of a primitive int.
Syntax:
Integer.valueOf(String s);
Example:
Integer number = Integer.valueOf("123");Explanation:
The valueOf() method converts the string "123" into an Integer object. This approach is useful when you need to work with Integer objects instead of primitive int values. If the string cannot be converted, a NumberFormatException will also be thrown.
Let's see an example code that will convert java string to int.
string s="69";
Integer integer = integer.valueOf(str);
System.out.println(integer);
Note: Similar to Integer.parseInt() A NumberFormatException will be thrown if the string does not include a valid number.
As a result, we must handle this exception every time we convert java string to int by placing the code within the try-catch block. Let's see the example and see the error that we will receive when we try to convert java string to int, which contains invalid input.
string s = "69P";
try
{
Integer integer = integer.valueOf(str);
System.out.println(integer);
}
catch (NumberFormatException ex)
{
ex.printStackTrace();
}Output
java.lang.NumberFormatException: For input string: "69P"
at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
at java.lang.Integer.parseInt(Integer.java:580)
at java.lang.Integer.valueOf(Integer.java:766)
at OOP.StringTest.main(StringTest.java:42)
Also check out Addition of Two Numbers in Java here.
569+ registered 
