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int a=7; // Example of Primitive data type
Sometime, primitive data types are not fulfilling the requirement of the user. In this type of situation, Java allows you use
composite data types. Composite data types are those data types that are defined by the user using the primitive data
types. In other words, a composite data type is a collection of primitive data types. Composite data types are also known
as non-primitive data types. There are mainly three composite data types used in Java which are class, array and interface.
int ar[] = new int[10]; // Example of Composite data type
The ar[] is an array containing 10 integer values. We will learn about array later in this book. Another example of
composite data type is String. String is a class that is a collection of char data type.
13.2 CLASS AS A COMPOSITE DATA TYPE
As you know that a class contains data members and member methods. Data members are the primitive data types
and member methods use these data members. Hence, a class can also be considered as a composite data type. As it
is defined by the user, so it also called user-defined data type. A class may be considered as a new data type created by
the user that has its own functionality.
13.3 DIFFERENCE BETWEEN PRIMITIVE AND COMPOSITE DATA TYPES
Primitive Data Type Composite Data Type
It predefined data type. It is user-defined data type.
It always contains a value. It can also contain null values.
It always starts with lowercase letter. It can start with lowercase or uppercase letter.
13.4 INTRODUCTION TO WRAPPER CLASSES
Wrapper classes are the in-built classes that contain primitive data types. These classes are used to convert primitive
data types into objects and vice-versa with the help of their methods. Every wrapper class has various methods too
Thus, providing a way to use the primitive data types (short, double, boolean, etc.) as objects. Every primitive data type
is attached to its wrapper class. For example, the float data type is attached to the Float class, the double data type is
attached to the Double class, and so on.
All the wrapper classes are part of java.lang package in the Java library. The eight wrapper classes in java.lang package
are given below:
Wrapper Class Primitive Data Type
Boolean boolean
Character char
Byte byte
Short short
Integer int
Long long
Float float
Double double
13.4.1 Need for Using a Wrapper Class
Wrapper classes are used:
a. To allow primitive data types to convert from one data type to another.
b. To store primitive data types as objects.
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