InstanceOfJava

Implement java 8 functional interface using lambda example program

Posted by: Instanceofjava Posted date: 11:32 PM / comment : 0 Java 8 , java programming interview questions

Functional interfaces introduces in java 8 .
Functional interfaces will have single abstract method in it.
Check here for full details on Java 8 functional interface with example.
Functional interfaces will be implemented by java 8 Lamda expressions.
Lets see an example program on how can we use functional interfaces or how can we implement functional interfaces using Lamda expression in java 8.
Create one functional interface with one abstract method in it.
Create a class and implement this abstract method using Lamda Expressions.

#1: Java example program to create functional interface.

functional interface example in java 8 using lamda expressions

#2: Java example program to implement functional interface using Lamda expressions in java 8.

package com.instanceofjava.java8;
/**
* @author www.Instanceofjava.com
* @category interview programming questions
*
* Description: java 8 Lamda expressions
*
*/
public class LamdaExpressions {
public static void main(String[] args) {
FunctionalInterfaceExample obj = ()->{
System.out.println("hello world");
};
obj.show();
}
}

Output:

hello world

Java 8 functional interface with example

Posted by: Instanceofjava Posted date: 11:04 PM / comment : 0 Java 8 , java programming interview questions

Java 8 introduced Lamda expressions and functional interfaces.
An interface with one abstract method is known as functional interfaces.
Functional interfaces in java 8 marked with @FunctionalInterface.
These functional interfaces implementation will be provided by Lamda expressions.
Default methods in java 8 interfaces are not abstract methods. But we can define multiple default methods in functional interface.
Java 8 functional interface example program

#1: Java Example program to create java 8 functional interface.

package com.instanceofjava.java8;
/**
* @author www.Instanceofjava.com
* @category interview programming questions
*
* Description: java 8 functional interfaces
*
*/
@FunctionalInterface
public interface FunctionalInterfaceExample {
void show();
}

Can we create functional interface with @FunctionalInterface annotation without any single abstract method?
No. Functional interfaces must have single abstract method inside it.
It will throw compile time error : Invalid '@FunctionalInterface' annotation; FunctionalInterfaceExample is not a functional interface.
Lets see an example program on this so that we can conclude it.
How to use these functional interfaces we will discuss in next post on Lamda expressions.
Implement java 8 functional interface using lambda example program

#2: What will happend if we define functional interface without a single abstract method in it?

Java 8 date add n seconds to current date example program

Posted by: Instanceofjava Posted date: 8:33 PM / comment : 0 Java 8 , java programming interview questions

Java 8 providing java.time.LocalDateTime class.
By using plusSeconds() method of LocalDateTime we can add seconds to date.
By Using minusSeconds() method we can substract seconds from java date.
Lets see an example java program to add n seconds to current date and minus / subtract n seconds from java 8 date.

#1: Java Example program to add n seconds to current date using java 8.

package com.instanceofjava.java8;
import java.time.LocalDateTime;
/**
* @author www.Instanceofjava.com
* @category interview programs
*
* Description: java seconds to java 8 date
*
*/
public class addSecondsToDate {
public static void main(String[] args) {
//create data using java 8 LocalDateTime
LocalDateTime datetime= LocalDateTime.now();
System.out.println("Before: "+datetime);
//add seconds by using plusSeconds(seconds) method
datetime=datetime.plusSeconds(12);
System.out.println("After: "+datetime);
}
}

Output:

2018-02-03T20:19:25.760
2018-02-03T20:19:37.760

#2: Java Example program to subtract n seconds to current date using java 8.

java 8 date subtract seconds example program

Java 8 stream filter method example program

Posted by: Instanceofjava Posted date: 7:42 PM / comment : 0 java Collections interview Questions , java interview programs , java8

We can use java 8 stream class filter method to filter the values from a list /map in java
By Using filter() and collect() methods of stream class we can achieve this.
Lets see an example program to filter value from list without using java 8 streams and with java 8 stream filter.

#1: Java Example program to filter . remove value from list without using java 8 stream

package com.instanceofjava.filtermethodjava8
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
/**
* @author www.Instanceofjava.com
* @category interview programs
*
* Description: Remove value from list without using java 8 stream filter method
*
*/
public class fillterListJava8{
private static List<String> filterList(List<String> fruits, String filter) {
List<String> result = new ArrayList<>();
for (String fruit : fruits) {
if (!filter.equals(fruit)) {
result.add(fruit);
}
}
return result;
}
public static void main(String[] args) {
List<String> fruits = Arrays.asList("apple", "banana", "lemon");
System.out.println("Before..");
for (String str : fruits) {
System.out.println(str);
}
List<String> result = filterList(fruits, "lemon");
System.out.println("After..");
for (String str : result) {
System.out.println(str);
}
}
}

Output:

Before..
apple
banana
lemon
After..
apple
banana

#2: Java Example program to filter . remove value from list using java 8 java.util.stream

package com.instanceofjava.java8;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;
/**
* @author www.Instanceofjava.com
* @category interview programs
*
* Description: Remove value from list using java 8 stream filter method
*
*/
public class filterMethodOfStream {
public static void main(String[] args) {
List<String> fruits = Arrays.asList("apple", "banana", "lemon");
String value="lemon";
List<String> result = fruits.stream()
.filter(line -> !value.equals(line))
.collect(Collectors.toList());
result.forEach(System.out::println);
for (String str : result) {
System.out.println(str);
}
}
}

Output:

How to remove html tags from string java

Posted by: Instanceofjava Posted date: 6:55 PM / comment : 0 java interview programs , java string interview programs

If you want to remove html tags from a string in java you need to use regex.
Using java regex we can trim/remove html tags from given string.
Lets see a java example program on how can we remove html code or html tags from a string in java.
Input String : hello
output: hello

#1: Java Example program to remove html tags from a string

package com.instanceofjava.removehtmltags;
/**
* @author www.Instanceofjava.com
* @category interview programs
*
* Description: java convert html to plain text/ trim html code from string in java
*
*/
public class RemoveHtmlTags {
public static void main(String[] args) {
String htmlStr = "Java Program to remove html tags from a String";
System.out.println(htmlStr);
htmlStr = htmlStr.replaceAll("\\<.*?\\>", "");
System.out.println(htmlStr);
}
}

Output:

Java Program to remove html tags from a String
Java Program to remove html tags from a String

Java 8 foreach example program

Posted by: Instanceofjava Posted date: 12:12 AM / comment : 0 Java 8 , java interview programs

Java 8 introduces for each loop.
before that lest see an example of how normal java for each loop.

#1: Java Example program which explain use of for each loop.

package com.instanceofjava.java8;
import java.util.HashMap;
import java.util.Map;
public class ForEachLoop {
/**
* @author www.Instanceofjava.com
* @category interview questions
*
* Description: java 8 for each loop
*
*/
public static void main(String[] args) {
Map<String, Integer> stumarks = new HashMap<>();
stumarks.put("Sai", 65);
stumarks.put("Vamshi", 65);
stumarks.put("Mahendar", 76);
stumarks.put("Muni", 87);
stumarks.put("Manohar", 90);
for (Map.Entry<String, Integer> entry : stumarks.entrySet()) {
System.out.println(entry.getKey() + " marks : " + entry.getValue());
}
}
}

Output:

Muni marks : 87
Vamshi marks : 65
Mahendar marks : 76
Sai marks : 65
Manohar marks : 90

#2: Java Example program which explains the use of for each loop in java 8

In the above program we used for each loop to get key value pairs of map.
Same thing will be done in java 8 by using stumarks.forEach((k,v)->System.out.println( k + " marks : " + v));

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