Wrapper classes in Java

Wrapper classes: Java provides a rich set of wrapper classes. Wrapper classes are used to convert primitive data.

Integer class: A wrapper around the data type “int”.

Constructor:

1. Integer(int num); Constructs an integer object from an integer variable.
   
2. Integer(String str); Constructs an “Integer” object from a “String” object.

import java.lang.*;
class App50
{
public static void main(String yck[])
{
int z;
z=10;
Integer x=new Integer(z);
String s=new String("200");
Integer y=new Integer(s);
System.out.println(x);
System.out.println(y);
}
}


output:

\>javac App50.java
\>java App50
10
200

Methods:

1. byte byteValue(); Converts to byte.
   
2. double doubleValue(); Converts to double.
   
3. float floatValue(); Converts to float.
   
4. int intValue(); Converts to int.
   
   
5. long longValue(); Converts to long.
   
6. short shortValue(); Converts to short.
   
7. String toString(); Converts to String.

import java.lang.*;
class App51
{
public static void main(String yck[])
{
int x;
x=10;
Integer i1=new Integer(x);

byte b;
b=i1.byteValue();
System.out.println("byte equivalent :"+b);

double d;
d=i1.doubleValue();
System.out.println("double equivalent :"+d);

float f;
f=i1.floatValue();
System.out.println("float equivalent :"+f);

int p;
p=i1.intValue();
System.out.println("int equivalent :"+p);

long l;
l=i1.longValue();
System.out.println("long equivalent :"+l);

short s;
s=i1.shortValue();
System.out.println("short equivalent :"+s);

String s1;
s1=i1.toString();
System.out.println("String equivalent :"+s1);
}
}


output:

\>javac App51.java
\>java App51
byte equivalent :10
double equivalent :10.0
float equivalent :10.0
int equivalent :10
long equivalent :10
short equivalent :10
String equivalent :10

Static StringtoBinaryString(int num); Converts to binary format.

Static StringtoHexString(int num); Converts to hexadecimal format.

Static StringtoOctalString(int num); Converts to octal format.

Note: “Static” methods of the class can be invoked directly with the name of the class. To use them you need not create objects.

import java.lang.*;
class App52
{
public static void main(String yck[])
{
System.out.println(Integer.toBinaryString(10));
System.out.println(Integer.toHexString(10));
System.out.println(Integer.toOctalString(10));
}
}


output:

\>javac App52.java
\>java App52
1010
a
12


Static int.parseInt(String str); Converts the contents of the object 'str' into 'int' data type.

import java.lang.*;
class App53
{
public static void main(String yck[])
{
String s1=new String("100");
String s2=new String("200");
int sum=Integer.parseInt(s1)+Integer.parseInt(s2);
System.out.println("The sum of two strings is : "+sum);
}
}


output:

\>javac App53.java
\>java App53
The sum of two strings is : 300

boolean equals(object integerobject); Returns true if the invoking integer object is equivalent to integerobject.

int compareTo(integer); Compares the numerical value of the invoking object with that of given integers.