Java 8 initialize set with values with an example program

Posted by: Instanceofjava Posted date: 9:05 PM / comment : 0 ,

  • We can initialize set while defining by passing values to constructor.
  • For example to initialize HashSet we can use Arrays.asList(value1,value2).
  • Set<Integer> hashset = new HashSet<>(Arrays.asList(12, 13));

#1: Java Example program to initialize set without using java 8

  1. import java.util.Arrays;
  2. import java.util.HashSet;
  3. import java.util.Set;
  4. /**
  5.  * @author www.Instanceofjava.com
  6.  * @category interview questions
  7.  * 
  8.  * Description: Initialize set 
  9.  *
  10.  */
  11. public class InitializeSet {

  13. public static void main(String[] args) {

  15. Set<Integer> hashset = new HashSet<>(Arrays.asList(12, 13));
  16. System.out.println(hashset);
  17. }

  19. }

Output:

  1. [12, 13]


  • We can initialize set in java 8 using Stream.
  • Stream.of("initialize", "set").collect(Collectors.toSet());



#2: Java Example program to initialize set without using java 8

  2. import java.util.Set;
  3. import java.util.stream.Collectors;
  4. import java.util.stream.Stream;
  5. /**
  6.  * @author www.Instanceofjava.com
  7.  * @category interview questions
  8.  * 
  9.  * Description: Initialize set using java 8 Stream
  10.  *
  11.  */
  12. public class InitializeSet {

  14. public static void main(String[] args) {

  16. Set<String> set = Stream.of("initialize", "set").collect(Collectors.toSet());
  17. System.out.println(set);
  18. }

  20. }



Output:

  1. [set, initialize]


  • We can initialize Set in java 8 by creating stream from an Array and list


#3: Java Example program to initialize set without using java 8


java 8 initialize set with values with an example program

Java 8 stream filter method example program

Posted by: Instanceofjava Posted date: 7:42 PM / comment : 0 , ,

  • 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

  1. package com.instanceofjava.filtermethodjava8

  3. import java.util.ArrayList;
  4. import java.util.Arrays;
  5. import java.util.List;

  7. /**
  8.  * @author www.Instanceofjava.com
  9.  * @category interview programs
  10.  * 
  11.  * Description: Remove value from list without using java 8 stream filter method
  12.  *
  13.  */
  14. public class fillterListJava8{
  16. private static List<String> filterList(List<String> fruits, String filter) {
  17.         List<String> result = new ArrayList<>();
  18.         for (String fruit : fruits) {
  19.             if (!filter.equals(fruit)) { 
  20.                 result.add(fruit);
  21.             }
  22.         }
  23.         return result;
  24.     }
  25. public static void main(String[] args) {
  27. List<String> fruits = Arrays.asList("apple", "banana", "lemon");
  28.  
  29. System.out.println("Before..");
  30.  
  31. for (String str : fruits) {
  32.             System.out.println(str);    
  33.         }
  34.  
  35.         List<String> result = filterList(fruits, "lemon");
  36.         System.out.println("After..");
  37.         for (String str : result) {
  38.             System.out.println(str);    
  39.         }
  40. }
  42. }

 Output:
  2. Before..
  3. apple
  4. banana
  5. lemon
  6. After..
  7. apple
  8. banana

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

  3. package com.instanceofjava.java8;

  5. import java.util.ArrayList;
  6. import java.util.Arrays;
  7. import java.util.List;
  8. import java.util.stream.Collectors;

  10. /**
  11.  * @author www.Instanceofjava.com
  12.  * @category interview programs
  13.  * 
  14.  * Description: Remove value from list using java 8 stream filter method
  15.  *
  16.  */

  18. public class filterMethodOfStream {

  20. public static void main(String[] args) {
  22. List<String> fruits = Arrays.asList("apple", "banana", "lemon");
  23. String value="lemon";
  24. List<String> result = fruits.stream()                
  25.                 .filter(line -> !value.equals(line))     
  26.                 .collect(Collectors.toList());             
  27.         result.forEach(System.out::println); 
  28.        
  29.         for (String str : result) {
  30.             System.out.println(str);    
  31.         }
  32. }

  35. }






Output:


java 8 stream filter method

How to subtract N hours from current date time using java 8

Posted by: Instanceofjava Posted date: 11:22 PM / comment : 0 ,

  • We have already seen how to subtract number of days from java using calendar and using java 8.
  • How to subtract X days from a date using Java calendar and with java 8 
  • Now we will discuss here how to subtract hours from java 8 localdatetime.
  • Some times we will get out date time in string format so we will convert our string format date to java 8 LocaDateTime object.
  • We can user DateTimeFormatter to tell the format of date time to LocalDateTime class.
  • LocalDateTime datetime = LocalDateTime.parse(currentTime,formatter);
  • LocalDateTime has minusHours(numberOfHours) method to subtract hours from date time.
  • Lets see an example java program to subtract hours from java date time using java 8 LocalDateTime class.
  • How to subtract hours from java 8 date time.



Program #1 : Java Example Program to subtract hours from given string formatted date time using java 8.



  1. package java8;
  2. /**
  3.  * By: www.instanceofjava.com
  4.  * program: how to subtract hours from date time using java 8  
  5. *
  6.  */
  7. import java.time.LocalDateTime;
  8. import java.time.format.DateTimeFormatter;
  9.  
  10. public class SubstractHoursJava{
  12. public static void main(String[] args) {
  13.  
  14.   DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
  15.  
  16.         String currentTime= "2017-10-19 22:00:00";
  18.  
  19.         System.out.println("Before subtraction of hours from date: "+currentTime);
  20.  
  21.         LocalDateTime datetime = LocalDateTime.parse(currentTime,formatter);
  22.  
  23.         datetime=datetime.minusHours(4);
  24.  
  25.         String aftersubtraction=datetime.format(formatter);
  26.         System.out.println("After 4 hours subtraction from date: "+aftersubtraction);
  28.  
  29.     }
  30.  
  31. }

Output:

  1. Before subtraction of hours from date: 2017-10-19 22:00:00
  2. After 4 hours subtraction from date: 2017-10-19 18:00:00

  • Now we will see how to subtract one hour from current date time in java using java 8 

Program #2 : Java Example Program to subtract one hour from given current date time using java 8.

  1. package java8;
  2. /**
  3.  * By: www.instanceofjava.com
  4.  * program: how to subtract hours from date time using java 8  
  5. *
  6.  */
  7. import java.time.LocalDateTime;
  8. import java.time.format.DateTimeFormatter;
  9.  
  10. public class SubtractOneHour {
  11.  
  12. public static void main(String[] args) {
  13.  
  14.   DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd H:mm:ss");
  15.  
  16.         LocalDateTime datetime = LocalDateTime.now();
  17.         System.out.println("Before subtraction of hours from date: "+datetime.format(formatter));
  19.  
  20.        datetime=datetime.minusHours(1);
  21.        String aftersubtraction=datetime.format(formatter);
  22.        System.out.println("After 1 hour subtraction from date: "+aftersubtraction);
  24.  
  25.     }
  26.  
  27. }
Output:


  1. Before subtraction of hours from date: 2017-10-19 23:14:12
  2. After 1 hour subtraction from date: 2017-10-19 22:14:12

subtract hours from java date time
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