Convert String to numeric data type in Java

Converting String to numeric values

To convert String data type to numeric data type we can use wrapper classes of numeric primitives.

public class Main {
    public static void main(String[] args) {
        String strNum = "12";
        int num = Integer.parseInt(strNum);
        System.out.println(num); // 12
    }
} 

We convert similarly for other numeric data types by using their wrapper class versions.

public class Main {
    public static void main(String[] args) {
        String strNum = "12av";
        // NumberFormatException here 
        int num = Integer.parseInt(strNum); 
        System.out.println(num); 
    }
}

If we try to convert a string that is not a number(the content of the string is not a number), we will get NumberFormatException which is a runtime exception.

Converting numeric data type into String data type is quite easy.

public class Main {
    public static void main(String[] args) {
        int num = 10;
        String str = "" + num;
    }
}

The String is a special class and everything that concatenates with string will become a string. So the easiest way is to just concatenate.

public class Main {
    public static void main(String[] args) {
        int num = 10;
        String str = String.valueOf(num);
    }
}

Another way is using valueOf method of String to convert numeric data to String.

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This article is part of the series of articles to learn Java programming language from Tech Lead Academy:
Introduction to programming 
OS, File, and File System
Working with terminal 
Welcome to Java Programming Language
Variables and Primitives in Java
Convert String to numeric data type
Input from the terminal in Java
Methods with Java
Java Math Operators and special operators
Conditional branching in Java
Switch statement in Java
Ternary operator in Java
Enum in Java
String class and its methods in Java
Loops in Java
Access modifiers in Java
Static keyword in Java
The final keyword in Java
Class and Object in Java
Object-Oriented Programming in Java
OOP: Encapsulation in Java
OOP: Inheritance in Java
OOP: Abstraction in Java
OOP: Polymorphism in Java
The method Overriding vs Overloading in Java
Array in Java
Data Structures with Java
Collection framework in Java
ArrayList in Java
Set in Java
Map in Java
Date and Time in Java
Exception in Java
How to work with files in Java
Design Patterns
Generics in Java
Multithreading in java
Annotations in Java
Reflection in Java
Reflection & Annotations - The Powerful Combination
Run terminal commands from Java
Lambda in Java
Unit Testing in Java
Big O Notation for coding interviews
Top Java coding interview questions for SDET