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Articles on Trending Technologies
Technical articles with clear explanations and examples
Checking if a HashSet contains certain value in Java
Let’s say the following is our Integer array −Integer arr[] = { 50, 100, 150, 200, 250, 300 };Set the above integer array in HashSet −Setset = new HashSet(Arrays.asList(arr));Now, let us check whether the HashSet contains certain value or not −set.contains(150)TRUE is returned if the value is in the List, else FALSE is the return value.Exampleimport java.util.Arrays; import java.util.HashSet; import java.util.Set; public class Demo { public static void main(String[] a) { Integer arr[] = { 50, 100, 150, 200, 250, 300 }; Setset = new HashSet(Arrays.asList(arr)); System.out.println(set.contains(200)); ...
Read MoreCan we change return type of main() method in java?
The public static void main() method is the entry point of the Java program. Whenever you execute a program in Java, the JVM searches for the main method and starts executing from it.You can write the main method in your program with return type other than void, the program gets compiled without compilation errors. But, at the time of execution JVM does not consider this new method (with return type other than void) as the entry point of the program.It searches for the main method which is public, static, with return type void, and a String array as an argument.public static int ...
Read MoreMake a Hashtable read-only in Java
Read-only Hashtable would mean users won’t be able to add or remove elements from it. Let us first create a Hashtable with key-value pair −Hashtablehash = new Hashtable(); hash.put("1", "A"); hash.put("2", "B"); hash.put("3", "C"); hash.put("4", "D"); hash.put("5", "E"); hash.put("6", "F"); hash.put("7", "G");Now, use unmodifiableMap() to form a Hashtable read-only −Mapm = Collections.unmodifiableMap(hash);Exampleimport java.util.Collections; import java.util.Hashtable; import java.util.Map; public class Demo { public static void main(String[] s) { Hashtablehash = new Hashtable(); hash.put("1", "A"); hash.put("2", "B"); hash.put("3", "C"); hash.put("4", "D"); hash.put("5", "E"); ...
Read MoreDoubleStream count() method in Java
The count() method of the DoubleStream class returns the count of the elements in the stream.The syntax is as follows:long count()To use the DoubleStream class in Java, import the following package:import java.util.stream.DoubleStream;Create DoubleStream and add some elements:DoubleStream doubleStream = DoubleStream.of(50.8, 67.9, 35.7, 23.6, 89.9);Now, get the count of elements in the DoubleStream:long res = doubleStream.count();The following is an example to implement DoubleStream count() method in Java:Exampleimport java.util.stream.DoubleStream; public class Demo { public static void main(String[] args) { DoubleStream doubleStream = DoubleStream.of(50.8, 67.9, 35.7, 23.6, 89.9); long res = doubleStream.count(); System.out.println("Count ...
Read MoreJava Program to get the reverse of the NavigableSet
We will create a NavigableSet collection and add some elements −NavigableSet set = new TreeSet(); set.add("ABC"); set.add("DEF"); set.add("GHI"); set.add("JKL"); set.add("MNO"); set.add("PQR"); set.add("STU");Now, use descendingSet() for the reverse of NavigableSet −NavigableSetreverse = set.descendingSet();Exampleimport java.util.NavigableSet; import java.util.TreeSet; public class Demo { public static void main(String[] args) { NavigableSet set = new TreeSet(); set.add("ABC"); set.add("DEF"); set.add("GHI"); set.add("JKL"); set.add("MNO"); set.add("PQR"); set.add("STU"); NavigableSetreverse = set.descendingSet(); System.out.println("NavigableSet = " + set); System.out.println("NavigableSet ...
Read MoreLongStream sum() method in Java
The sum() method of the LongStream class returns the sum of elements in this stream.The syntax is as followslong sum()To use the LongStream class in Java, import the following packageimport java.util.stream.LongStream;First, create an IntStream and add some elementsLongStream longStream = LongStream.of(100L, 30000L, 45000L, 55000L, 70000L);Now, add the elements of the streamlong res = longStream.sum();The following is an example to implement LongStream sum() method in JavaExampleimport java.util.stream.LongStream; public class Demo { public static void main(String[] args) { LongStream longStream = LongStream.of(100L, 30000L, 45000L, 55000L, 70000L); long res = longStream.sum(); System.out.println("The sum ...
Read MoreHow to rethrow an exception in Java?
Sometimes we may need to rethrow an exception in Java. If a catch block cannot handle the particular exception it has caught, we can rethrow the exception. The rethrow expression causes the originally thrown object to be rethrown.Because the exception has already been caught at the scope in which the rethrow expression occurs, it is rethrown out to the next enclosing try block. Therefore, it cannot be handled by catch blocks at the scope in which the rethrow expression occurred. Any catch blocks for the enclosing try block have an opportunity to catch the exception.Syntaxcatch(Exception e) { System.out.println("An exception ...
Read MoreIntStream summaryStatistics() method in Java
The summaryStatistics() method in the IntStream class is used to return summary data about the elements of this stream. The syntax is as follows:IntSummaryStatistics summaryStatistics()Create an IntStream and add some elements:IntStream intStream = IntStream.of(30, 60, 90);Now, get the summary data about the above elements:IntSummaryStatistics details = intStream.summaryStatistics();The following is an example to implement IntStream summaryStatistics() method in Java:Exampleimport java.util.stream.IntStream; import java.util.IntSummaryStatistics; public class Demo { public static void main(String[] args) { IntStream intStream = IntStream.of(30, 60, 90); IntSummaryStatistics details = intStream.summaryStatistics(); System.out.println("Details = "+details); } }OutputDetails = IntSummaryStatistics{count=3, sum=180, ...
Read MoreJava Program to get day of week for the last day of each month in 2019
For last day of each month, at first create a List collection for day of week −ListdayOfWeek = new ArrayList();Now, get day of week for the last day of each month in 2019, set the year using withYear() and use lastDayOfMonth() and getDayOfWeek methods −for (Month m: Month.values()) { DayOfWeek days = LocalDate.now().withYear(2019).with(m).with(TemporalAdjusters.lastDayOfMonth()).getDayOfWeek(); }Exampleimport java.time.DayOfWeek; import java.time.LocalDate; import java.time.Month; import java.time.temporal.TemporalAdjusters; import java.util.ArrayList; import java.util.List; public class Demo { public static void main(String[] argv) { ListdayOfWeek = new ArrayList(); for (Month m: Month.values()) { DayOfWeek days = LocalDate.now().withYear(2019).with(m).with(TemporalAdjusters.lastDayOfMonth()).getDayOfWeek(); ...
Read MoreLongStream.Builder add() method in Java
The add() method of the LongStream.Builder class in Java adds an element to the stream being built. The method returns this builder.The syntax is as followsdefault LongStream.Builder add(long i)Here, i is the input.To use the LongStream.Builder class in Java, import the following packageimport java.util.stream.LongStream;Create LongStream.Builder and add some elementsLongStream.Builder builder = LongStream.builder();Add some elements in the streambuilder.add(150L); builder.add(200L); builder.add(500L); builder.add(250L);The following is an example to implement LongStream.Builder add() method in JavaExampleimport java.util.stream.LongStream; public class Demo { public static void main(String[] args) { LongStream.Builder builder = LongStream.builder(); builder.add(150L); builder.add(200L); ...
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