This document discusses inner classes, including: - The different types of inner classes - member classes, local classes, and anonymous classes - How to use classes from other packages by importing them - Examples of inner class code showing member classes, local classes, and using imported classes The key points are that inner classes allow classes to be defined within other classes, the different types have specific characteristics like whether they can have static members or not, and importing is needed to use classes from other packages in a Java file. Examples are provided to illustrate these concepts.

1. Objectives
On completion of this period, you would be
able to learn
• Inner classes
• Using classes from other packages
• Importing packages
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2. Recap
Access protection
• To protect the access of members of an object
• Done with the help of access modifiers
• private, public, protected
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3. Inner Classes
• Inner classes ?
• We know what is nesting
• Nested if
• Nested looping
• Nested blocks
• Likewise, classes can also be nested
• And such a class is an example of inner class
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4. Inner Classes Contd..
• Classes can be defined as members of other
classes
• Classes can also be defined within a block of
Java code
• Types
• Member class
• Local Class
• Anonymous Class
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5. Member Class
• A class defined as a member (non-static) of
another
• Can use members of enclosing classes
• Cannot have static members
• Cannot have same name as a containing class
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6. Example
public class A {
public String name = "a";
public class B {
public String name = "b";
public class C {
public String name = "c";
public void print_names() {
System.out.println(name); // "c": name field of class C
System.out.println(this.name);// "c": name field of class C
System.out.println(C.this.name);// "c": name field of class
C
System.out.println(B.this.name); // "b": name field of classB
System.out.println(A.this.name);// "a": name field of class A
}
}
}
}
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7. Example Contd..
class Member Class Test {
public static void main (String[] args ) {
A a = new A(); // Create an instance of A.
A.B b = a. new B(); // Create an instance of B within the
instance of A.
A.B.C c = b. new C(); // Create an instance of C within the
instance of B.
c. print _ names(); // Invoke a method of the instance of c.
} Output
}
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8. Local Class
• A class defined in a block of code
• Can use members of enclosing classes
• Cannot have static members
• Cannot have same name as a containing class
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9. Anonymous Class
• Unnamed class defined within an expression
• Can use members of enclosing classes
• Cannot have static members
• Cannot have same name as a containing class
• Has no name or constructor
• Only one instance of the class is created
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10. Summary
• In this class we have discussed
• Inner classes
• Types of inner classes
• Different ways of using a class from other
package
• Import statement
• Some example programs
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11. Frequently Asked Questions
1. What is inner class ?
2. List the types of inner classes
3. What are the different ways of using a class
defined in other package?
4. Write a program in Java that illustrates the use of
import statement
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12. Quiz
1. Among the following which is NOT an inner
class ?
1. Member Class
2. Local Class
3. Implicit Class
4. Anonymous Class
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13. Quiz Contd..
2. Which package is imported by default ?
1. java. util.*
2. java. lang.*
3. java. sql.*
4. java. net.*
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14. Quiz Contd..
3. How many import statements can a Java
class contain?
1. Only one
2. Two
3. Three
4. Zero or more
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15. Quiz Contd..
4. Which of the following class has no name ?
Member Class
Anonymous Class
Local Class
Inner Class
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