CBSE Class 11 Informatics Practices Chapter 2 Introduction to Programming Languages Part 2

Class Notes of Chapter 2: Introduction to Programming Languages

Class 11th Informatics Practices
Part 2

Introduction to Programming Languages

      Topics:

• Data Types
• Primitive Data Types
• Reference Data Types
• Type Conversion

 
Data Types

There are two data types available in Java:
Primitive Data Types
Reference/Object Data Types




Primitive Data Types

There are eight primitive data types supported by Java. Primitive data types are predefined by the language and named by a keyword.

• byte

1. Byte data type is an 8-bit signed two's complement integer.
2. Minimum value is -128 (-2^7)
3. Maximum value is 127 (inclusive)(2^7 -1)
4. Default value is 0
5. Byte data type is used to save space in large arrays, mainly in place of integers, since a byte is four times smaller than an int.
6. Example: byte a = 100 , byte b = -50

• short

1. The short data type is a 16-bit signed two's complement integer.
2. Minimum value is -32,768 (-2^15)
3. Maximum value is 32,767 (inclusive) (2^15 -1)
4. Short data type can also be used to save memory as byte data type. A short is 2 times smaller than an int
5. Default value is 0.
6. Example: short s = 10000, short r = -20000

• int

1. int data type is a 32-bit signed two's complement integer.
2. Minimum value is - 2,147,483,648.(-2^31)
3. Maximum value is 2,147,483,647(inclusive).(2^31 -1)
4. int is generally used as the default data type for integral values unless there is a concern about memory.
5. The default value is 0.
6. Example: int a = 100000, int b = -200000

• long

1. Long data type is a 64-bit signed two's complement integer
2. Minimum value is -9,223,372,036,854,775,808.(-2^63)
3. Maximum value is 9,223,372,036,854,775,807 (inclusive). (2^63 -1)
4. This type is used when a wider range than int is needed.
5. Default value is 0L.
6. Example: long a = 100000L, int b = -200000L

• float

1. Float data type is a single-precision 32-bit IEEE 754 floating point.
2. Float is mainly used to save memory in large arrays of floating point numbers.
3. Default value is 0.0f.
4. Float data type is never used for precise values such as currency.
5. Example: float f1 = 234.5f

• double

1. double data type is a double-precision 64-bit IEEE 754 floating point.
2. This data type is generally used as the default data type for decimal values, generally the default choice.
3. Double data type should never be used for precise values such as currency.
4. Default value is 0.0d.
5. Example: double d1 = 123.4

• boolean

1. boolean data type represents one bit of information. 21
2. There are only two possible values: true and false.
3. This data type is used for simple flags that track true/false conditions.
4. Default value is false.
5. Example: boolean one = true

• char

1. char data type is a single 16-bit Unicode character.
2. Minimum value is '\u0000' (or 0).
3. Maximum value is '\uffff' (or 65,535 inclusive). • Char data type is used to store any character.
4. Example: char letterA ='A'

Reference Data Types

• Reference variables are created using defined constructors of the classes. They are used to access objects. These variables are declared to be of a specific type that cannot be changed. For example, Employee, Puppy etc.
• Class objects, and various type of array variables come under reference data type.
• Default value of any reference variable is null. • A reference variable can be used to refer to any object of the declared type or any compatible type.Example: Animal animal = new Animal("giraffe");

Type Conversion

Java supports two types of castings – primitive data type casting and reference type casting. Reference type casting is nothing but assigning one Java object to another object. It comes with very strict rules and is explained clearly in Object Casting. Now let us go for data type casting. Java data type casting comes with 2 flavors.

1. Implicit Casting
2. Explicit Casting

• Implicit Casting (Widening Conversion)

A data type of lower size (occupying less memory) is assigned to a data type of higher size. This is done implicitly by the JVM. The lower size is widened to higher size. This is also named as automatic type conversion.

Examples:
int x = 10; // occupies 4 bytes
double y = x; // occupies 8 bytes
System.out.println(y); // prints 10.0
In the above code 4 bytes integer value is assigned to 8 bytes double value.

• Explicit casting (narrowing conversion)

A data type of higher size (occupying more memory) cannot be assigned to a data type of lower size. This is not done implicitly by the JVM and requires explicit casting; a casting operation to be performed by the programmer. The higher size is narrowed to lower size.
double x = 10.5; // 8 bytes
int y = x; // 4 bytes ; raises compilation error In the above code, 8 bytes value is narrowed to 4 bytes int value. It raises error. Let us explicitly type cast it.
double x = 10.5;
int y = (int) x;