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Passing Behavior 

 
/**
 * LAMBDAS - PASSING BEHAVIOR, NOT OBJECTS
 * ---------------------------------------
 * Before Java 8, anonymous inner classes were the primary way to
 * pass 'behavior' (code) as a parameter.
 * 
 * Lambdas allow us to pass 'behavior' (a block of code) insteed of 
 * passing an object that wraps that behavior.
 * 
 * A lambdas expression:
 *  - has no name
 *  - implements a functional interface
 */

package com.minte9.lambdas.anonymous_inner_classes;

import javax.swing.JButton;
import javax.swing.JFrame;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class PassingBehavior {
    public static void main (String[] args) {
        
        JFrame frame = new JFrame("Inner Class vs Lambda");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(400, 200);

        // ---------------------------------------------
        // Button 1 - Annonymous Inner Class (old style)
        // ---------------------------------------------
        JButton buttonInner = new JButton("Inner Class");
        buttonInner.addActionListener(
            new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    System.out.println("Clicked via INNER CLASS");
                }
            }
        );

        // ---------------------------------------------------
        // Button 2 - Lambda Expressions (modern style)
        // ---------------------------------------------------
        JButton buttonLambda = new JButton("Lambda");
        buttonLambda.addActionListener(
            event -> System.out.println("Clicked via LAMBDA")
        );

        // ---------------------------------------------------
        // Layout 
        // ---------------------------------------------------
        frame.getContentPane().setLayout(new java.awt.FlowLayout());
        frame.getContentPane().add(buttonInner);
        frame.getContentPane().add(buttonLambda);        
        frame.setVisible(true);

    }
}

Real Example 

 
/**
 * ANNONYMOUS INNER CLASS vs LAMBDA - REAL LIFE EXAMPLE
 * ----------------------------------------------------
 * Scenario:
 *  We have a list of orders and want to sort them by price.
 * 
 * This example demonstrate:
 *   1) Sorting with an anonymous inner class (pre-Java 8)
 *   2) Sorting with a lambda expression (Java 8+)
 * 
 * Both approaches pass behavior (comparition logic) to the sort() method.
 */

package com.minte9.lambdas.anonymous_inner_classes;

import java.util.ArrayList;
import java.util.Comparator;
import java.util.List;

public class RealExample {
    public static void main(String[] args) {

        List<Order> orders = new ArrayList<>();
        orders.add(new Order("Book", 15.99));
        orders.add(new Order("Laptop", 1200.));
        orders.add(new Order("Pen", 1.50));

        // -------------------------------------
        // 1) Anonymous Inner Class (pre-Java 8)
        // --------------------------------------
        orders.sort(
            new Comparator<Order>() {
                @Override
                public int compare(Order o1, Order o2) {
                    return Double.compare(o1.price(), o2.price());
                }
            }
        );
        System.out.println("Sorted with Inner Class:");
        orders.forEach(System.out::println);

        // -------------------------------------
        // 2) Lambda Expressions (Java 8+)
        // --------------------------------------
        orders.sort(
            (o1, o2) -> Double.compare(o1.price(), o2.price())
        );
        System.out.println("Sorted using lambda:");
        orders.forEach(System.out::println);
    }
}

record Order(String name, double price) {}

Lambda Definition 

 
/**
 * WHAT ARE LAMBDAS?
 * -----------------
 * A lambda expression is a concise way to represent implementations
 * of functional interfaces.
 * 
 * A functional interface is an interface with one abstract method.
 * 
 * Insteed of creating an object with an anonymous inner class,
 * lambdas allow us to pass 'behavior' (executable code) directly.
 * 
 * COMMON LAMBDAS FORMS:
 * ---------------------
 * () -> expresion          // no parameters
 * () -> { statement }      // multiple statements
 * (x, y) -> x + y          // multiple parameters
 */

package com.minte9.lambdas.anonymous_inner_classes;

import java.util.function.BinaryOperator;

public class LambdaDefinition {
    public static void main(String[] args) {

        // -----------------------------------
        // Lambda with no arguments (Runnable)
        // -----------------------------------
        Runnable noArgs = () -> System.out.println("Hello World");
        new Thread(noArgs).run();
        
        // --------------------------------------
        // Lambda with a full block of statements
        // --------------------------------------
        Runnable multiStatement = () -> {
            System.out.println("Hello");
            System.out.println("World");
        };
        new Thread(multiStatement).run();

        // ---------------------------------------
        // Lambda with parameters (BinaryOperator)
        // ---------------------------------------
        BinaryOperator<Integer> op = (x, y) -> x + y;
        System.out.println(op.apply(2, 3));  // 5
    }
}






Questions and answers:
Clink on Option to Answer




1. What do lambdas allow you to pass to a method?

  • a) Only objects
  • b) Behavior (executable code)

2. Before Java8 how was behavior commonly passed to methods?

  • a) Using anonymous inner classes
  • b) Using lambda expressions

3. What type of interface does a lambda implement?

  • a) Any interface
  • b) A functional interface (one abstract method)

4. Why are lambdas considered more readable than anonymous inner classes?

  • a) They remove boilerplate code
  • b) They require more setup

5. In sorting examples, what behavior is being passed?

  • a) Data storage logic
  • b) Comparison logic

6. What is a key characteristic of a lambda expression?

  • a) It must be declared in a separate class
  • b) It has no name

7. Why are lambdas described as “passing behavior, not objects”?

  • a) Because Java no longer supports objects
  • b) Because logic is passed directly instead of being wrapped in a class


References: