EkumeedHelp: December 2019

Function vs Predicate

December 29, 2019 Add Comment

In this post, we will check out the difference between Function and Predicate functional interface in java 8.

Java 8 : Function

December 26, 2019 Add Comment

What is a Function?

This is a predefined functional interface like Predicate, present in java.util.function package. It has one abstract method called apply();

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interface Function<T,R> {
   public R apply(T t);
 }

Function example 1: to check the length of the string.

package com.blogspot.ekumeedkiasha;

import java.util.function.Function;

public class FunctionExample1 {

 public static void main(String[] args) {
  Function<String, Integer> fun = s -> s.length();
  System.out.println(fun.apply("ekumeedhelp"));
 }

}

Function Chaining example:

package com.blogspot.ekumeedkiasha;

import java.util.function.Function;

public class FunctionChaining {

 public static void main(String[] args) {

  int amount = 3;

  Function<Integer, Integer> sum = i -> i + i; // 3 + 3 = 6

  Function<Integer, Integer> sq = i -> i * i; // 6 * 6 = 36

  System.out.println(sum.apply(amount));

  System.out.println(sq.apply(amount));

  System.out.println(sum.andThen(sq).apply(amount));

  System.out.println(sum.compose(sq).apply(amount));

 }

}

Java 8 : Predicates

December 21, 2019 Add Comment

Predicate Example to find out all the even numbers in the given array.

package com.blogspot.ekumeedkiasha;

import java.util.function.Predicate;

/*
 * find out all the even numbers in the given array
 */
public class PredicateExample2 {

 public static void main(String[] args) {

  int[] num = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };

  Predicate<Integer> even = x -> x % 2 == 0;

  for (int i : num) {
   if (even.test(i)) {
    System.out.println(i);
   }
  }

 }

}

Predicate Joining Example:

Interface predicate has three default methods.

1. and(Predicate p)
2. or(Predicate p)
3. negate()

find out all the even numbers which are greater than 5 in the given array.

package com.blogspot.ekumeedkiasha;

import java.util.function.Predicate;

/*
 * Q1. Find out all the even numbers in the given array.
 * 
 * Q2. Find out all the number which is greater than 5 in the given array.
 */
public class PredicateExample2 {

 public static void main(String[] args) {

  int[] num = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };

  Predicate<Integer> even = x -> x % 2 == 0;

  Predicate<Integer> grt = y -> y > 5;

  for (int i : num) {
   if (grt.or(even).test(i)) {
    System.out.println(i);
   }

}

}

}

For equality predicate interface has isEqual(Object o) method which is static.

Example:

package com.blogspot.ekumeedkiasha;

import java.util.function.Predicate;

public class PredicateExample3 {

 public static void main(String[] args) {
  Predicate<String> name = Predicate.isEqual("Mumbai");
  System.out.println(name.test("Mumbai"));
 }

}

Java 8 : Predicates

December 15, 2019 4 Comments

What is Predicate?

Java 8 comes with a concept of functional interface. An interface having only one abstract method and any number of default and static methods is called a functional interface.

A Predicate (boolean-valued function) of one argument which is present in java.util.function package. It is predefined functional interfaces that It has only one abstract method i.e, test().

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 interface Predicate<T> {
   public boolean test(T t);
 }

Predicate Example to check age is greater than 18 or not.

Step: -1

public boolean test(Integer age) {
 if (age > 18) {
  return true;
 } else {
  return false;
 }
}

Step -2

public class PredicateExample {

 public static void main(String[] args) {
  Predicate<Integer> p = age -> (age > 18);
  System.out.println(p.test(21));  // true
  System.out.println(p.test(17));  // false
 }

}

Predicate Example to check collection is empty or not

package com.blogspot.ekumeedkiasha;

import java.util.ArrayList;
import java.util.Collection;
import java.util.function.Predicate;

public class PredicateExample {

 public static void main(String[] args) {
  Predicate<Collection> p = c -> c.isEmpty();

  ArrayList<Object> al = new ArrayList<>();
  al.add("Monday");

  ArrayList<Object> al1 = new ArrayList<>();

  System.out.println(p.test(al)); // false
  System.out.println(p.test(al1)); // true
 }

}

Java 8 : Lambda with Thread Example

December 04, 2019 6 Comments

Hello Friends,
Thank you for visiting this blog. This is the continuation of my Java 8 video series tutorials which was published in youtube channel ekumeedhelp.

In this post, we will be learning about the use of Java 8 lambda expression in Thread.

Create Thread without using lambda
Example:- 1

//https://ekumeedkiasha.blogspot.com/
package com.blogspot.ekumeedkiasha;

public class Main {

 public static void main(String[] args) {
  Runnable r = new CodeToRun();
  Thread t = new Thread(r);
  t.start();
  for (int i = 0; i < 10; i++) {
   System.out.println("Main Thread i = " + i);
  }
 }
}

class CodeToRun implements Runnable {

 @Override
 public void run() {
  for (int i = 0; i < 10; i++) {
   System.out.println("CodeToRun Thread i = " + i);
  }

 }

}

Create Thread with Lambda Example
Example:- 2

//https://ekumeedkiasha.blogspot.com/
package com.blogspot.ekumeedkiasha;

public class Main {

 public static void main(String[] args) {
  Runnable r = () -> {
   for (int i = 0; i < 10; i++) {
    System.out.println("CodeToRun Thread i = " + i);
   }
  };

  Thread t = new Thread(r);
  t.start();
  for (int i = 0; i < 10; i++) {
   System.out.println("Main Thread i = " + i);
  }
 }
}

Create Thread using Anonymous class
Example:- 3

//https://ekumeedkiasha.blogspot.com/
package com.blogspot.ekumeedkiasha;

public class Main {

public static void main(String[] args) {

  Thread t = new Thread(new Runnable() {
   public void run() {
    for (int i = 0; i < 10; i++) {
     System.out.println("CodeToRun Thread i = " + i);
    }
   }
  });
  t.start();
  for (int i = 0; i < 10; i++) {
   System.out.println("Main Thread i = " + i);
  }
 }
}