Type Casting

Type Casting

Assigning a value of one type to a variable of another type is known as Type Casting.

Example :

int x = 10;
byte y = (byte)x;

In Java, typecasting is classified into two types,

Widening Casting(Implicit)

Narrowing Casting(Explicitly done)

Widening or Automatic type conversion

Automatic Type casting take place when,

• the two types are compatible
• the target type is larger than the source type

Example :

public class Test
{
    public static void main(String[] args)
    {
      int i = 100; 
      long l = i; //no explicit type casting required  
      float f = l; //no explicit type casting required  
      System.out.println("Int value "+i);
      System.out.println("Long value "+l);
      System.out.println("Float value "+f);
    }
    
}

Output :

Int value 100
Long value 100
Float value 100.0

Narrowing or Explicit type conversion

When you are assigning a larger type value to a variable of smaller type, then you need to perform explicit type casting.

Example :

public class Test
{
    public static void main(String[] args)
    {
      double d = 100.04;  
      long l = (long)d;  //explicit type casting required  
      int i = (int)l; //explicit type casting required  
      
      System.out.println("Double value "+d);
      System.out.println("Long value "+l);
      System.out.println("Int value "+i);
     
    }
    
}

Output :

Double value 100.04
Long value 100
Int value 100

Java Variable

A variable is a container which holds the value while the java program is executed. A variable is assigned with a datatype.

Variable is a name of the memory location. There are three types of variables in Java: local, instance and static.

There are two types of data types in Java: primitive and non-primitive.

Variable

The variable is a name of a reserved area allocated in memory. In other words, it is a name of a memory location. It is a combination of "vary + able" that means its value can be changed.

Types of Variable

There are three types of variables in Java:

• local variable
• instance variable
• static variable

1) Local Variable

A variable declared inside the body of the method is called local variable. You can use this variable only within that method and the other methods in the class aren't even aware that the variable exists.

A local variable cannot be defined with "static" keyword.

2) Instance Variable

A variable declared inside the class but outside the body of the method, is called the instance variable. It is not declared as static.

It is called instance variable because its value is instance specific and is not shared among instances.

3) Static variable

A variable which is declared as static is called static variable. It cannot be local. You can create a single copy of static variable and share among all the instances of the class. Memory allocation for static variable happens only once when the class is loaded in the memory.

Example to understand the types of variables in java

class A
{
  int data=50;  //instance variable
  static int m=100;  //static variable
  void method()
  {
    int n=90;  //local variable
  }
}   //end of class

Java Variable Example: Add Two Numbers

class Simple{
public static void main(String[] args){
int a=10;
int b=10;
int c=a+b;
System.out.println(c);
}}

Output:

20

Java Variable Example: Widening

class Simple{
public static void main(String[] args){
int a=10;
float f=a;
System.out.println(a);
System.out.println(f);
}}

Output:

10
10.0

Java Variable Example: Narrowing (Typecasting)

class Simple{
public static void main(String[] args){
float f=10.5f;
//int a=f;//Compile time error
int a=(int)f;
System.out.println(f);
System.out.println(a);
}}

Output:

10.5
10