Wrapper Classes in Java

Wrapper Classes In Java

We know that when we pass any "Command Line Argument" through the command prompt and which is directly sending to the main method ( main ( ) ), It is available in the form "Array of object of String class" (String args[]). The string type of data we cannot perform any numerical operations. 

 So hence it is designed to convert string type data into numerical / fundamental type data by using wrapper classes.

Define Wrapper class & Explain its purpose

For each & every fundamental data types their exist one pre-defined class then it is also known as "Wrapper classes".  The purpose of Wrapper class is that to convert String data type into numerical / fundamental data type values. 

The following table gives fundamental data type with  corresponding wrapper class name & conversion method which will convert string type of  data into fundamental type data.

In generally each & every Wrapper class contain the following method whose purpose into convert string data type into numerical / fundamental data type.
                      
                                              Wrapper class name
                                                                 🔺
Public  static  xxx  parse xxx ( String )

Here note that xxxx represents any fundamental data type( Expect char data type ).

Points to Remembers to use Methods In a Class.

1. Beside the  what type of method (instance or static method) We are using and presenting which class.

2. Beside what type of parameters a method is taking and pass it values return type.

3. Beside what type of method is returning and hold the result in a variable of return type.

EX:-   Math ↴

             int  sum( int,int ) 
The below example will shown how to useful in the wrapper classes in java.

Math m = new Math(  );
int x  = m. sum ( 10,20 );

System.out.println(x) = //30.

EX 1:- String s = "100";
            S = s + 2

            System.out.println ( S );     //1002 (invalid)

Here the value of s is declared as  "100" , In java if any values put  into a  "100"  then it called as String. So String type of values as  convert into fundamental type by using Wrapper class.

  int a = Integer.parseInt(s) // wrapper class name

  a = a+2;    // valid

 System.out.println(a);    // 102

EX : 2 String S1 = " 10.5f";

              S1  =  S1+2; 

              System.out.println( s1 );    // 10.5f2 ( invalid ) 

float x = Float. parseFloat ( s1 );  // wrapper class name

x = x+2;   // valid

System.out.println(x); //12.5f

EX : 3

String s [ ] = { "10", "20"};   10/20

System.out.println( s[0] + s[1] );  //1020 (invalid)

int x = Integer.parse Int ( s[0] );  // wrapper class name

int y = Integer.parse Int ( s[1] );  // wrapper class name

int z = x+y;   

⧭ Here we will discuss more examples on wrapper class.

System.out.println ( "sum="+z);        //sum=30 (valid)
System.out.println("sum="+x+y);    //sum1020

System.out.println ("sum="+x+y);   //sum=30

System.out.println(="mul"=+x+y);  //mul=200

System.out.println ("sub="+x-y);     //error

System.out.println("sub="+(y-x));   //sub=10

System.out.println("div="+x/y);      //Div=D

System.out.println ("MOD="+y/x);  //mod=0