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Wrapper Classes
Prepared By
Soni Axay R. (130240116056)
5th
IT
Guided By
Prof. Hiral Shastri

Sub Topics
飪� Introduction
飪� Primitives & Wrappers
飪� Use of Wrapper Classes
飪� Wrapper Object Creation
飪� MAX_VALUE Constant
飪� Examples

Introduction
飦� In Java, the term wrapper class commonly
refers to a set of Java classes that 鈥渙bjectify鈥�
the primitive Java types.
飦� That is, for each primitive type, there is a
corresponding Java 鈥淲rapper鈥� class that represents
that type.
飦� e.g. the wrapper for the int type is the Integer
class.

Primitives & Wrappers
飦� Java has a wrapper class for each of the eight primitive data types:
Primitive
Type
Wrapper
Class
Primitive
Type
Wrapper
Class
boolean Boolean float Float
byte Byte int Integer
char Character long Long
double Double short Short

Use of the Wrapper Classes
飦� Java鈥檚 primitive data types (boolean, int, etc.) are not
classes.
飦� Wrapper classes are used in situations where objects
are required, such as for elements of a Collection:
List<Integer> a = new
ArrayList<Integer>();
methodRequiringListOfIntegers(a);

Value => Object: Wrapper Object
Creation
飦� Wrapper.valueOf() takes a value
(or string) and returns an object
of that class:
Integer i1 = Integer.valueOf(42);
Integer i2 = Integer.valueOf(鈥�42鈥�);
Boolean b1 = Boolean .valueOf(true);
Boolean b2 = Boolean .valueOf(鈥渢rue鈥�);
Long n1 = Long.valueOf(42000000L);
Long n1 = Long.valueOf(鈥�42000000L鈥�);

Object => Value
飦� Each wrapper class Type has a method
typeValue to obtain the object鈥檚 value:
Integer i1 = Integer.valueOf(42);
Boolean b1 = Boolean.valueOf(鈥渇alse鈥�);
System.out.println(i1.intValue());
System.out.println(b1.intValue());
=>
42
false

String => value
飦� The Wrapper class for each primitive type has
a method parseType() to parse a string
representation & return the literal value.
Integer.parseInt(鈥�42鈥�) => 42
Boolean.parseBoolean(鈥渢rue鈥�) => true
Double.parseDouble(鈥�2.71鈥�) => 2.71
//鈥�
飦� Common use: Parsing the arguments to a
program:

Each Number Wrapper has a
MAX_VALUE constant:
byteObj = new Byte(Byte.MAX_VALUE);
shortObj = new Short(Short.MAX_VALUE);
intObj = new Integer(Integer.MAX_VALUE);
longObj = new Long(Long.MAX_VALUE);
floatObj = new Float(Float.MAX_VALUE);
doubleObj = new
Double(Double.MAX_VALUE);
printNumValues("MAXIMUM NUMBER
VALUES:");

MAX values (output from previous
slide):
=>
Byte:127
Short:32767
Integer:2147483647
Long:9223372036854775807
Float:3.4028235E38
Double:1.7976931348623157E308

Convert Integer to Java
String object
1.public听class听IntegerToStringExample听{
2.听
3.听听public听static听void听main(String[]听args)听{
4.听听听听Integer听intObj听=听new听Integer(10);
5.听听听
6.听听听听//use toString method of Integer class to conver Integer into String.
7.听听听听String听str听=听intObj.toString();
8.听听听听System.out.println("Integer听converted听to听String听as听"听+听str);
9.听听}
10.}
11.听
12./*
13.Output of the program would be
14.Integer converted to String as 10
15.*/

Convert Java Float Object
to String Object Example
1.听
3.听
4.听
5.听听听听Float听fObj听=听new听Float(10.25);
6.public听class听JavaFloatToStringExample听{
7.听听听听//use toString method of Float class to convert Float into String.
8.听听听听String听str听=听fObj.toString();
9.听听听听System.out.println("Float听converted听to听String听as听"听+听str);
10.听听}
11.}
12.听
13./*
15.Float converted to String as 10.25

Convert Byte object to
String object
听
1.public听class听ByteToStringExample听{
2.听
4.听听听听Byte听bObj听=听new听Byte("10");
5.听听听
6.听听听听//use toString method of Byte class to convert Byte into String.
7.听听听听String听str听=听bObj.toString();
8.听听听听System.out.println("Byte听converted听to听String听as听"听+听str);
9.听听}
10.}
11.听
13.Byte converted to String as 10
飦�

Convert Long object to
String object
1. public听class听LongToStringExample听{
2. 听
3. 听听public听static听void听main(String[]听args)听{
4. 听听听听Long听lObj听=听new听Long(10);
5. 听听听
6. 听听听听//use toString method of Long class to convert Long into String.
7. 听听听听String听str听=听lObj.toString();
8. 听听听听System.out.println("Long听converted听to听String听as听"听+听str);
9. 听听}
10. }
11. 听
12. /*
13. Output of the program would be
14. Long converted to String as 10

Convert Short object to
String object
1. public听class听ShortToStringExample听{
2. 听
3. 听听public听static听void听main(String[]听args)听{
4. 听听听听short听s听=听10;
5. 听听听听Short听sObj听=听new听Short(s);
6. 听听听
7. 听听听听//use toString method of Short class to convert Short into String.
8. 听听听听String听str听=听sObj.toString();
9. 听听听听System.out.println("Short听converted听to听String听as听"听+听str);
10. 听听}
11. }
12. 听
13. /*
14. Output of the program would be
15. Short converted to String as 10
16. */

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