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How to convert Strings into Numbers ?

There are two ways to convert Strings into Number :

1. The Number subclasses that wrap primitive numeric types Byte, Integer, Double, Float, Long, and Short each provide a class method named valueOf() that converts a String to an Object of that type.

Example : ValueOfDemo , that gets two strings from the command line, converts them to numbers, and performs arithmetic operations on the values

public class ValueOfDemo {
public static void main(String[] args) {

//this program requires two arguments on the command line
if (args.length == 2) {
//convert strings to numbers
float a = (Float.valueOf(args[0]) ).floatValue();
float b = (Float.valueOf(args[1]) ).floatValue();

//do some arithmetic
System.out.println("a + b = " + (a + b) );
System.out.println("a - b = " + (a - b) );
System.out.println("a * b = " + (a * b) );
System.out.println("a / b = " + (a / b) );
System.out.println("a % b = " + (a % b) );
} else {
System.out.println("This program requires two command-line arguments.");

The following is the output from the program when you use 4.5 and 87.2 for the command-line arguments :

a + b = 91.7
a - b = -82.7
a * b = 392.4
a / b = 0.0516055
a % b = 4.5

2. Each of the Number subclasses that wrap primitive numeric types also provides a parseXXXX() method (for example, parseFloat()) that can be used to convert Strings to primitive numbers. Since a primitive type is returned instead of an object, the parseFloat() method is more direct than the valueOf() method.

Example :

-Above ValueOfDemo program, we could use :

float a = Float.parseFloat(args[0]);
float b = Float.parseFloat(args[1]);
you can use static methods of wrapper classes to convert strings into primitive numbers
ex:int i= Integer.parseInt("10");
float i= Float.parseFloat("10.6");
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