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Lamdba Expression In Java

Lamdba Expression

  1. Lambda expression is available in java from jdk 1.8 onwards.
  2. Lambda Expression is use to achieve functional programming in java language.
  3. Functional Interface are required to use lamdba expression.
  4. Lambda Expression symbol (->)
  5. Lambda Expression is a process where, you can provide implementation for abstract method from functional interface.
  6. In Lambda expression internally create and anonymous class and return the object of that class.

 

Build in Functional Interface

  1. Build-in functional interface is present inside java.util.function package.
  2. Predicate:
    1. This is an functional interface which is present inside java.util.function package
    2. This interface has test method which accept one value and return Boolean.
    3. This interface in use to write a condition (filtrations).
  3. Function
    1. This is an functional interface which is present inside java.util.function package
    2. This interface has apply method which accept one value and return another.
    3. This interface is use to convert your value from one form to another.
  4. Supplier
    1. This is an functional interface which is present inside java.util.function package
    2. This interface has get method which return value.
    3. This interface is use to perform the execution and return the out of execution.
  5. Consumer
    1. This is an functional interface which is present inside java.util.function package
    2. This interface has accept method which accept and input parameter and not return anything.
    3. This interface is use to perform the execution on input value and not return the output.

 

LambdaIntro :-

public class LambdaIntro {

	public static void main(String[] args) {
		Inter a = () -> {
			System.out.println("This is lambda Expression");
		};
		execute(a);
	}

	private static void execute(Inter a) {
		a.print();
	}
	
}
@FunctionalInterface
interface Inter {
	void print();
}

 

Example :-

public class LambdaDemo1 {
	public static void main(String[] args) {
		Inter1 i1 = (val) -> 	System.out.println("The value is "+ val);
		
		i1.print("Ram");
		
		Inter2 i2 = (a, b) -> a+b;
		
		System.out.println(i2.add(12, 28));
		
		Inter3 i3 = (a ,b) -> a-b;
		
		System.out.println(i3.sub(12, 28));
	}
}
@FunctionalInterface
interface Inter1 {
	public void print(String val);
}
@FunctionalInterface
interface Inter2 {
	public int add(int a, int b);
}
@FunctionalInterface
interface Inter3{
	public int sub(int a, int b);
}

 

Lambda Demo 2 :-

import java.util.function.Function;
import java.util.function.Predicate;
import java.util.function.Supplier;

public class LambdaDemo2 {
	public static void main(String[] args) {
		Predicate obj = (val) -> val%2==0;
		System.out.println(obj.test(12));
		Predicate obj1 = (a) -> a%2==0;
		System.out.println(obj1.test(11));
		System.out.println("=============================");
		Function obj2 = (num) -> num*num; 
		System.out.println(obj2.apply(12));
		Supplier obj3 = () -> {
			return 23*23;
		
		};
		System.out.println(obj3.get());
	}
}

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