Inner classes in java
- Java inner classes are classes declared within other classes or interfaces. They allow grouping of logically related classes and interfaces and can access all members of the outer class, including private ones. - There are three main advantages of inner classes: they can access private members of the outer class, they make code more readable by grouping related classes, and they require less code. - The two types of inner classes are non-static (inner) classes and static nested classes. Non-static classes can access outer class members like private variables while static classes cannot access non-static members only static ones. - Examples demonstrate member inner classes, anonymous inner classes, local inner classes, and static nested classes in Java and how they can
![Java Member inner class In this example, we are creating msg()
method in member inner class that is accessing the private data
member of outer class.
class TestMemberOuter1{
private int data=30;
class Inner{
void msg(){System.out.println("data is "+data);}
}
public static void main(String args[]){
TestMemberOuter1 obj=new TestMemberOuter1();
TestMemberOuter1.Inner in=obj.new Inner();
in.msg();
}
}](https://image.slidesharecdn.com/innerclassesinjava-171219100318/85/Inner-classes-in-java-7-320.jpg)
![Java anonymous inner class example using class
abstract class Person{
abstract void eat();
}
class TestAnonymousInner{
public static void main(String args[]){
Person p=new Person(){
void eat(){System.out.println("nice fruits");}
};
p.eat();
}
}](https://image.slidesharecdn.com/innerclassesinjava-171219100318/85/Inner-classes-in-java-8-320.jpg)
![Java local inner class example
public class localInner1{
private int data=30;//instance variable
void display(){
class Local{
void msg(){System.out.println(data);}
}
Local l=new Local();
l.msg();
}
public static void main(String args[]){
localInner1 obj=new localInner1();
obj.display();
}
}](https://image.slidesharecdn.com/innerclassesinjava-171219100318/85/Inner-classes-in-java-9-320.jpg)
![Java static nested class example with
instance method
class TestOuter1{
static int data=30;
static class Inner{
void msg(){System.out.println("data is "+data);}
}
public static void main(String args[]){
TestOuter1.Inner obj=new TestOuter1.Inner();
obj.msg();
}
}](https://image.slidesharecdn.com/innerclassesinjava-171219100318/85/Inner-classes-in-java-11-320.jpg)
Inner classes in java
- 1. Java Inner Classes -Arulkumar V Assistant Professor, SECE
- 2. Interface in Java Java inner class or nested class is a class which is declared inside the class or interface. We use inner classes to logically group classes and interfaces in one place so that it can be more readable and maintainable. Additionally, it can access all the members of outer class including private data members and methods.
- 3. Syntax of Inner class class Java_Outer_class{ //code class Java_Inner_class{ //code } }
- 4. Advantage of java inner classes There are basically three advantages of inner classes in java. They are as follows: 1) Nested classes represent a special type of relationship that is it can access all the members (data members and methods) of outer class including private. 2) Nested classes are used to develop more readable and maintainable code because it logically group classes and interfaces in one place only. 3) Code Optimization: It requires less code to write.
- 5. Types of Nested classes There are two types of nested classes non-static and static nested classes. The non-static nested classes are also known as inner classes. >Non-static nested class (inner class) Member inner class Anonymous inner class Local inner class >Static nested class
- 6. Cont.,
- 7. Java Member inner class In this example, we are creating msg() method in member inner class that is accessing the private data member of outer class. class TestMemberOuter1{ private int data=30; class Inner{ void msg(){System.out.println("data is "+data);} } public static void main(String args[]){ TestMemberOuter1 obj=new TestMemberOuter1(); TestMemberOuter1.Inner in=obj.new Inner(); in.msg(); } }
- 8. Java anonymous inner class example using class abstract class Person{ abstract void eat(); } class TestAnonymousInner{ public static void main(String args[]){ Person p=new Person(){ void eat(){System.out.println("nice fruits");} }; p.eat(); } }
- 9. Java local inner class example public class localInner1{ private int data=30;//instance variable void display(){ class Local{ void msg(){System.out.println(data);} } Local l=new Local(); l.msg(); } public static void main(String args[]){ localInner1 obj=new localInner1(); obj.display(); } }
- 10. Java static nested class A static class i.e. created inside a class is called static nested class in java. It cannot access non-static data members and methods. It can be accessed by outer class name. ◦ It can access static data members of outer class including private. ◦ Static nested class cannot access non-static (instance) data member or method.
- 11. Java static nested class example with instance method class TestOuter1{ static int data=30; static class Inner{ void msg(){System.out.println("data is "+data);} } public static void main(String args[]){ TestOuter1.Inner obj=new TestOuter1.Inner(); obj.msg(); } }
- 12. Thank You 19-12-2017 Sampath Kumar.S, AP/IT 12