This document discusses Java wrapper classes. It introduces wrapper classes as classes that "objectify" the primitive Java types, with each primitive type having a corresponding wrapper class (e.g. Integer for int). It describes using wrapper classes for collection elements, creating wrapper objects from values using valueOf(), getting the primitive value from a wrapper object, parsing strings to primitive values, and MAX_VALUE constants in the number wrappers. Examples are provided for converting between Integer, Float, Byte, Long, Short, and string objects.

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

2. Sub Topics
 Introduction
 Primitives & Wrappers
 Use of Wrapper Classes
 Wrapper Object Creation
 MAX_VALUE Constant
 Examples

3. Introduction
 In Java, the term wrapper class commonly
refers to a set of Java classes that “objectify”
the primitive Java types.
 That is, for each primitive type, there is a
corresponding Java “Wrapper” class that represents
that type.
 e.g. the wrapper for the int type is the Integer
class.

4. Primitives & Wrappers
 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

5. Use of the Wrapper Classes
 Java’s primitive data types (boolean, int, etc.) are not
classes.
 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);

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

7. Object => Value
 Each wrapper class Type has a method
typeValue to obtain the object’s value:
Integer i1 = Integer.valueOf(42);
Boolean b1 = Boolean.valueOf(“false”);
System.out.println(i1.intValue());
System.out.println(b1.intValue());
=>
42
false

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

9. 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:");

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

11. Integer

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

13. Float

14. Convert Java Float Object
to String Object Example
1.
2. public static void main(String[] args) {
3.
4.
5. Float fObj = new Float(10.25);
6.public class JavaFloatToStringExample {
7. //use toString method of Float class to convert Float into String.
8. String str = fObj.toString();
9. System.out.println("Float converted to String as " + str);
10. }
11.}
12.
13./*
14.Output of the program would be
15.Float converted to String as 10.25

15. Byte

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

17. Long

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

19. Short

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

21. Thank You