To rotate a list in Java, let us first create a List and add elements −List < Integer > list = new ArrayList < Integer > (); list.add(5); list.add(10); list.add(15); list.add(20); list.add(25); list.add(30); list.add(35); list.add(40); list.add(45);Now, rotate the list −Collections.reverse(list);Example Live Demoimport java.util.ArrayList; import java.util.Collections; import java.util.List; public class Demo {    public static void main(String args[]) {       Listlist = new ArrayList();       list.add(5);       list.add(10);       list.add(15);       list.add(20);       list.add(25);       list.add(30);       list.add(35);       list.add(40);       list.add(45); ... Read More

Let us first create a Java List and add elements −ArrayList < String > list = new ArrayList < String > (); list.add("Katie"); list.add("Tom"); list.add("Jack"); list.add("Amy"); list.add("Andre"); list.add("Brad"); list.add("Peter"); list.add("Bradley");Now, use ListIterator and return the next element in the List with next() −ListIteratoriterator = list.listIterator(); iterator.next();Replace the element in the List with set() method. Here, whatever element is set will get replaced as the first element of the Iterator −iterator.set("Angelina");Example Live Demoimport java.util.ArrayList; import java.util.ListIterator; public class Demo {    public static void main(String[] args) {       ArrayListlist = new ArrayList();       list.add("Katie");       list.add("Tom"); ... Read More

Set implementations in Java has only unique elements. Therefore, it can be used to remove duplicate elements.Let us declare a list and add elements −List < Integer > list1 = new ArrayList < Integer > (); list1.add(100); list1.add(200); list1.add(300); list1.add(400); list1.add(400); list1.add(500); list1.add(600); list1.add(600); list1.add(700); list1.add(400); list1.add(500);Now, use the HashSet implementation and convert the list to HashSet to remove duplicates −HashSetset = new HashSet(list1); Listlist2 = new ArrayList(set);Above, the list2 will now have only unique elements.Example Live Demoimport java.util.ArrayList; import java.util.HashSet; import java.util.List; public class Demo {    public static void main(String[] argv) {       Listlist1 = new ArrayList(); ... Read More

With this, get the milliseconds in days, hours and minutes. At first, set the Duration −Duration d1 = Duration.ofDays(20); Duration d2 = Duration.ofHours(100); Duration d3 = Duration.ofMinutes(150);Convert the above Duration to nanoseconds −System.out.println("Milliseconds in 20 days = "+d1.toMillis()); System.out.println("Milliseconds in 100 hours = "+d2.toMillis()); System.out.println("Milliseconds in 150 minutes = "+d3.toMillis());Example Live Demoimport java.time.Duration; public class Demo {    public static void main(String[] args) {       Duration d1 = Duration.ofDays(20);       Duration d2 = Duration.ofHours(100);       Duration d3 = Duration.ofMinutes(150);       System.out.println("Milliseconds in 20 days = "+d1.toMillis());       System.out.println("Milliseconds in 100 hours ... Read More

Create a TreeSet first to get the lowest and highest value:TreeSet treeSet = new TreeSet();Add elements to the TreeSet:treeSet.add(50); treeSet.add(100); treeSet.add(150); treeSet.add(200); treeSet.add(250); treeSet.add(300); treeSet.add(400); treeSet.add(500); treeSet.add(800); treeSet.add(1000);Now, get the lowest value and highest value from the above TreeSet, which are 50 and 1000 respectively:treeSet.first(); treeSet.last();Exampleimport java.util.TreeSet; public class Demo {    public static void main(String[] args) {       TreeSet treeSet = new TreeSet();       treeSet.add(50);       treeSet.add(100);       treeSet.add(150);       treeSet.add(200);       treeSet.add(250);       treeSet.add(300);       treeSet.add(400);       treeSet.add(500);     ... Read More

To get HeadSet from TreeSet, at first create a TreeSet and add some elements:TreeSet treeSet = new TreeSet(); treeSet.add("ABC"); treeSet.add("DEF"); treeSet.add("GHI"); treeSet.add("JKL"); treeSet.add("MNO"); treeSet.add("PQR");To get headset, use the headset() method:SortedSet set = treeSet.headSet("MNO"); System.out.println("Head Set = " + set);You can also change the value like this:set = treeSet.headSet("GHI"); System.out.println("Head Set = " + set);Exampleimport java.util.SortedSet; import java.util.TreeSet; public class Demo {    public static void main(String[] args) {       TreeSet treeSet = new TreeSet();       treeSet.add("ABC");       treeSet.add("DEF");       treeSet.add("GHI");       treeSet.add("JKL");       treeSet.add("MNO");       treeSet.add("PQR"); ... Read More

To display a TreeSet in reverse order, you need to use Comparator. Let us first create an Integer array and use it for the TreeSet elements:Integer arr[] = { 25, 100, 125, 200, 250, 400, 450, 550, 600, 700};Now, use reverseOrde() comparator to reverse the natural ordering:Set set = new TreeSet(Collections.reverseOrder());Now, add individual elements of the set as the Integer array elements:for (int i = 0, l = arr.length; i < l; i++) {    set.add(arr[i]); }Exampleimport java.util.Collections; import java.util.Set; import java.util.TreeSet; public class Demo {    public static void main(String args[]) throws Exception {       Integer arr[] ... Read More

To create a TreeSet with custom comparator, let us first create a an Integer array and set it to TreeSetInteger arr[] = { 10, 20, 30, 40, 50, 60, 70, 80, 90, 100 }; Set set = new TreeSet(Collections.reverseOrder());Above, we have used the Comparator with reverseOrder(), which returns a comparator that imposes the reverse of the natural ordering.Exampleimport java.util.Collections; import java.util.Set; import java.util.TreeSet; public class Demo {    public static void main(String args[]) throws Exception {       Integer arr[] = { 10, 20, 30, 40, 50, 60, 70, 80, 90, 100 };       Set set = ... Read More

Let’s say you need to convert Instant to LocalDateTime with IST with timezone:Create an Instant:Instant instant = new Date().toInstant();Now, convert Instant to LocalDateTime:LocalDateTime date = LocalDateTime.ofInstant(instant, ZoneId.of(ZoneId.SHORT_IDS.get("IST")));Exampleimport java.time.Instant; import java.time.LocalDateTime; import java.time.ZoneId; import java.util.Date; public class Demo {    public static void main(String[] args) {       Instant instant = new Date().toInstant();       LocalDateTime date = LocalDateTime.ofInstant(instant, ZoneId.of(ZoneId.SHORT_IDS.get("IST")));       System.out.println("Date (IST) = " + date);       date = LocalDateTime.ofInstant(instant, ZoneId.of(ZoneId.SHORT_IDS.get("PST")));       System.out.println("Date (PST) = " + date);       date = LocalDateTime.ofInstant(instant, ZoneId.of(ZoneId.SHORT_IDS.get("EST")));       System.out.println("Date (EST) = " ... Read More

At first, set a LocalDate:LocalDate localDate = LocalDate.of(2019, Month.FEBRUARY, 2);Now, adjust the LocalDate to next Tuesday using next() method:LocalDate date = localDate.with(TemporalAdjusters.next(DayOfWeek.TUESDAY));Exampleimport java.time.DayOfWeek; import java.time.LocalDate; import java.time.Month; import java.time.temporal.TemporalAdjusters; public class Demo {    public static void main(String[] args) {       LocalDate localDate = LocalDate.of(2019, Month.FEBRUARY, 2);       System.out.println("Current Date = "+localDate);       System.out.println("Current Month = "+localDate.getMonth());       LocalDate date = localDate.with(TemporalAdjusters.firstDayOfMonth());       System.out.println("First day of month = "+date);       date = localDate.with(TemporalAdjusters.next(DayOfWeek.TUESDAY));       System.out.println("Next Tuesday date = "+date);    } }OutputCurrent Date = 2019-02-02 Current ... Read More