Type casting
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Type casting is the process of converting an object or variable from one data type to another, with widening being the safe conversion from a lower to a higher data type, and narrowing being the potentially unsafe conversion from a higher to a lower data type. Data types are categorized into primitive and referenced types, with type casting possible between classes that have an inheritance relationship. Generalization and specialization describe the phenomena of promoting subclasses to superclasses and narrowing superclasses to subclasses, respectively.
![Widening in referenced data
types
ClassTest
{
public static void main{String args[]}
{
One o;
o = (One) newTwo();
o.show1();
}
}
Note : we are able to access show1() method of the super
class. But in this case, it is not possible to call show2().](https://image.slidesharecdn.com/typecasting-190704071938/85/Type-casting-9-320.jpg)
Type casting
- 1. ● Type casting is used to convert an object or variable of one type into another. ●Assigning a value of one type to a variable of another type is known as type casting. Syntax : dataType variableName = (dataType) variableToConvert ;
- 2. Type Casting Types of Data Types ◦ Primitive or Fundamental Data Types ◦ Referenced or Advanced Data Types • Casting Primitive Data Type ▫ Widening - Converting lower data type into higher data type is called widening. ▫ Narrowing – Converting a higher data type into lower data type is called narrowing.
- 4. WIDENING IN PRIMITIVE DATA TYPES Char ch = ‘A’ ; int num = ( int ) ch ; int x = 9500 ; float sal = ( float ) x ; Widening is safe because there will not be any loss of data. That is why, compiler does the casting internally and hence this is called “Implicit Casting”.
- 5. int x = 66 ; char ch = ( char ) x ; double d = 12.6879 ; int n = ( int ) d ; Narrowing is not safe because there will be loss of data. That is why, compiler forces the programmer to use cast operator and hence this is called “Explicit Casting”.
- 6. Casting Referenced Data Types A class is referenced data type. Converting a class type into another class type is also possible through casting. But the classes should have the same relationship between them by the way of inheritance. University ↑ College ↑ Department
- 7. Type Casting Generalization : Generalization is a phenomenon where a sub class is promoted to a super class, and hence becomes more general . It needs widening or up-casting. Specialization : Specialization is a phenomenon where a super class is narrowed down to a sub class. It needs narrowing or down-casting.
- 8. Class One { void show1() { System.out.println (“I am class one“); } } class Two extends One { void show1() { System.out.println(“I am class Two”); } }
- 9. Widening in referenced data types ClassTest { public static void main{String args[]} { One o; o = (One) newTwo(); o.show1(); } } Note : we are able to access show1() method of the super class. But in this case, it is not possible to call show2().