lambda expression code example

Example 1: lambda expressions in java

A lambda expression is a short block 
of code which takes in parameters
and returns a value. Lambda expressions
are similar to methods, but they do
not need a name and they can be
implemented right in the body of a method.

parameter -> expression

To use more than one parameter, wrap them in parentheses:

(parameter1, parameter2) -> expression

Example
Use a lamba expression in the ArrayList's 
forEach() method to print every item in the list:

import java.util.ArrayList;

public class Main {
  public static void main(String[] args) {
    ArrayList<Integer> numbers = new ArrayList<Integer>();
    numbers.add(5);
    numbers.add(9);
    numbers.add(8);
    numbers.add(1);
    numbers.forEach( (n) -> { System.out.println(n); } );
  }
}

Example 2: lambda expressions

A lambda expression is a short block 
of code which takes in parameters
and returns a value. Lambda expressions
are similar to methods, but they do
not need a name and they can be
implemented right in the body of a method.

parameter -> expression

To use more than one parameter, wrap them in parentheses:

(parameter1, parameter2) -> expression

Example
Use a lamba expression in the ArrayList's 
forEach() method to print every item in the list:

import java.util.ArrayList;

public class Main {
  public static void main(String[] args) {
    ArrayList<Integer> numbers = new ArrayList<Integer>();
    numbers.add(5);
    numbers.add(9);
    numbers.add(8);
    numbers.add(1);
    numbers.forEach( (n) -> { System.out.println(n); } );
  }
}

Example 3: c# lambdas

//Lambdas are just short handed anonymous method or functions usally 
//for use in passing to other methods or functions to call such as a sort.
//Example:
//The Lambda used here after the =s
Action ExampleContainerForDelagate = ()=>
	{/*Do something such as this example*/
    	Console.WriteLine("Hello world");
	};
//has been shorted from this anonymous delegate or method.
Action ExampleContainerForDelagate = delegate () { Console.WriteLine("Hello world"); };
//And this full (named) method signature method passing
Action ExampleContainerForDelagate = ExampleMethod;
void ExampleMethod()
{ Console.WriteLine("Hello world"); }
//usage example
List<int> ExampleList = new List(){1,3,0};
ExampleList.Sort((x,y)=>{return x - y; });
//The Sort will sort based on the return values from the Lambda passed.
//a negative will be seen as a smaller than the next number
//a 0 will be seen as equal
//and a positive will be seen as bigger than the next number
//by switching x and y postion in the 'return x - y;' you will effectively 
//change the sort to descending order. This is there for useful for sorting 
//based on needs or where it is not obvious how to sort.

Example 4: how to use lambda in java

StateOwner stateOwner = new StateOwner();

stateOwner.addStateListener(
    (oldState, newState) -> System.out.println("State changed")
);

Example 5: whats a lambda

// C++ program to demonstrate lambda expression in C++
#include <bits/stdc++.h>
using namespace std;
  
// Function to print vector
void printVector(vector<int> v)
{
    // lambda expression to print vector
    for_each(v.begin(), v.end(), [](int i)
    {
        std::cout << i << " ";
    });
    cout << endl;
}
  
int main()
{
    vector<int> v {4, 1, 3, 5, 2, 3, 1, 7};
  
    printVector(v);
  
    // below snippet find first number greater than 4
    // find_if searches for an element for which
    // function(third argument) returns true
    vector<int>:: iterator p = find_if(v.begin(), v.end(), [](int i)
    {
        return i > 4;
    });
    cout << "First number greater than 4 is : " << *p << endl;
  
  
    // function to sort vector, lambda expression is for sorting in
    // non-decreasing order Compiler can make out return type as
    // bool, but shown here just for explanation
    sort(v.begin(), v.end(), [](const int& a, const int& b) -> bool
    {
        return a > b;
    });
  
    printVector(v);
  
    // function to count numbers greater than or equal to 5
    int count_5 = count_if(v.begin(), v.end(), [](int a)
    {
        return (a >= 5);
    });
    cout << "The number of elements greater than or equal to 5 is : "
         << count_5 << endl;
  
    // function for removing duplicate element (after sorting all
    // duplicate comes together)
    p = unique(v.begin(), v.end(), [](int a, int b)
    {
        return a == b;
    });
  
    // resizing vector to make size equal to total different number
    v.resize(distance(v.begin(), p));
    printVector(v);
  
    // accumulate function accumulate the container on the basis of
    // function provided as third argument
    int arr[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
    int f = accumulate(arr, arr + 10, 1, [](int i, int j)
    {
        return i * j;
    });
  
    cout << "Factorial of 10 is : " << f << endl;
  
    //     We can also access function by storing this into variable
    auto square = [](int i)
    {
        return i * i;
    };
  
    cout << "Square of 5 is : " << square(5) << endl;
}

Example 6: lambda expressions

A lambda expression is a short block 
of code which takes in parameters
and returns a value. Lambda expressions
are similar to methods, but they do
not need a name and they can be
implemented right in the body of a method.

parameter -> expression

To use more than one parameter, wrap them in parentheses:

(parameter1, parameter2) -> expression

Example
Use a lamba expression in the ArrayList's 
forEach() method to print every item in the list:

import java.util.ArrayList;

public class Main {
  public static void main(String[] args) {
    ArrayList<Integer> numbers = new ArrayList<Integer>();
    numbers.add(5);
    numbers.add(9);
    numbers.add(8);
    numbers.add(1);
    numbers.forEach( (n) -> { System.out.println(n); } );
  }