Java-8 (The Biggest Transformation)

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Java 8 is the update that completely changed how Java developers write code. It took Java from “old-school, verbose, class-heavy” to clean, modern, expressive.

Today we starts with LAMBDA EXPRESSION(Part-1)

In Java, writing even a small piece of logic used to be lengthy because we had to create an anonymous class and override its method every single time. Java 8 solved this problem by introducing lambda expressions — a short, clean, functional‑style way to write code.

Basic Syntax
(parameters)−>body

Variations
No parameter- ()->System.out.println("HI");
One parameter-x->x*x;
Multiple parameter- (x,y)->x*y;
// with blocks with parameter return is must
With Blocks- x->{int y=x+1; return y;};
// with blocks with void return is no need
with Blocks with void- ()->{ system.out.println("HI"); }

Before 8:

new Thread(new Runnable() {
@override
public void run() {
System.out.println("Running");
}
}).start();
After 8:

new Thread(() -> System.out.println("Running")).start();

Capturing variables

Rule: Variable must be “effectively final”

int processedCount = 0;

orders.forEach(order -> {
processedCount++; // ❌ ERROR
});
Local variable processedCount defined in an enclosing scope must be final or effectively final
How to fix,

Fix 1: Use AtomicInteger

AtomicInteger processedCount = new AtomicInteger(0);

orders.forEach(order -> {
processedCount.incrementAndGet(); // ✔ Works
});
Atomic Integer is an object.

Java allows change the variable

Because Object reference is final but we change the values.

AtomicInteger sum = new AtomicInteger(0);

list.forEach(n -> sum.addAndGet(n));

System.out.println(sum.get());

Fix 2: Use array wrapper

int[] processedCount = {0};

orders.forEach(order -> {
processedCount[0]++; // ✔ Works
});
Any reference is final we change their values so we can do

Fix 3: Use Stream count