Strings / Number Conversions

Converting Numbers to Strings

The most common way to turn any number into a string is using String.valueOf(), though a quick "hack" is to concatenate the number with an empty string. 

 

// Method 1: The standard way

int age = 25;

String s1 = String.valueOf(age);

 

// Method 2: The shortcut

int age = 25;

String s2 = age + "";

 

Converting Strings to Numbers

To turn a string back into a number, you use "Wrapper Classes" (like Integer or Double). These classes provide "parse" methods. Note: If the string contains non-numeric characters (like "25a"), Java will throw a NumberFormatException.

 

// To Integer

int i = Integer.parseInt(numericText);

 

// To Double

double d = Double.parseDouble("19.99");

 

Summary of Common Conversion Methods
Target Type	Conversion Method
String	String.valueOf(number)
int	Integer.parseInt(string)
long	Long.parseLong(string)
double	Double.parseDouble(string

 

🎯 Simple Exam Definition

Number data types store numeric values used in calculations.

String data type stores text enclosed in double quotation marks.