I'am a newbie in JAVA and this came across this word called. "A class i.e. created inside a method is called local inner class in java. If you want to invoke the methods of local inner class, you must instantiate this class inside the method". The word in bold. Can anyone please help me out with this one.I know it's embarrassing and i should've researched more but I just cannot understand. Thanks.
First of all Declaring mean:
ClassName obj;
Simple meaning of instantiate is creating an object from class.
ClassName obj = new ClassName();
What is a object?
- An instance of a class. From one class we can create many instances.
- They are the basic runtime entities in in our program.
- They may also represent user-defined data types such as lists and vectors.
- Any programming problem is analyzed in terms of objects and nature of communication between them.
As a example:
//Define a reference(a variable) which can hold a `Person` obect.
Person p;
//Create a Person object(instantiate).
//new - use to allocate memory space for the new object
p = new Person();
What is a nested class?
A class that defined inside a class is called nested class. There 2 categories of nested classes.
Inner class:
- Inner class can only be accessed by the outer class. Not by any other class.
- Inner class is a member of outer class.
- Outer class can access inner class without importing.
- Inner class can access any attribute or a method belong to outer directly.
- Outer class cannot access directly to a inner class.
Example for a inner class:
class Outer{
int i = 10;
void main(){
//instantiate inner class.
Inner in = new Inner();
in.show();
}
class Inner{
void show(){
System.out.print(i);
}
}
}
What is a local class?
Which are classes that are defined in a block.
Example:
public class{
int i = 10;
public main(){
class A{
void show(){
System.out.println(i);
}
}
//inside the method instantiate local class.
A obj = new obj();
obj.show();
}
//outside the main() -block(method)
//inside another method instantiate local class.
public test(){
A obj = new A();
obj.show();
}
}