To generated random integer, use the Random class with nextInt. At first, create a Random object −Random rand = new Random();The Random above is a random number generator. Now, pick the random numbers one by one. We want 10 random four-digit numbers, therefore loop it until i = 1 to 10 −for (int i = 1; i

Let us first create an ArrayList −ArrayListarr = new ArrayList(); arr.add("50"); arr.add("100"); arr.add("150"); arr.add("200"); arr.add("250"); arr.add("300");Now, let’s say we have another Collection as Vector −Vectorvector = new Vector(); vector.add("500"); vector.add("700"); vector.add("800"); vector.add("1000"); Append all the elements from the Vector to ArrayList: arr.addAll(vector);Example Live Demoimport java.util.ArrayList; import java.util.Vector; public class Demo {    public static void main(String[] args) {       ArrayListarr = new ArrayList();       arr.add("50");       arr.add("100");       arr.add("150");       arr.add("200");       arr.add("250");       arr.add("300");       Vectorvector = new Vector();       vector.add("500");   ... Read More

Let us first create an ArrayList −ArrayList < Integer > arrList = new ArrayList < Integer > (); arrList.add(100); arrList.add(200); arrList.add(300); arrList.add(400); arrList.add(500);Now, create a ListIterator from the above ArrayList and insert more elements −ListIterator < Integer > iterator = arrList.listIterator(); iterator.add(1000); iterator.add(2000); iterator.add(3000);Example Live Demoimport java.util.ArrayList; import java.util.ListIterator; public class Demo {    public static void main(String[] args) {       ArrayListarrList = new ArrayList();       arrList.add(100);       arrList.add(200);       arrList.add(300);       arrList.add(400);       arrList.add(500);       arrList.add(600);       arrList.add(700);       arrList.add(800);     ... Read More

Let us first create an ArrayList −ArrayListarrList = new ArrayList(); arrList.add(10); arrList.add(50); arrList.add(100); arrList.add(150); arrList.add(250);Use Comparators interface to order in reverse order with reverseOrder() −Comparator comparator = Collections.reverseOrder(); Now, sort with Collections: Collections.sort(arrList, comparator);Example Live Demoimport java.util.ArrayList; import java.util.Collections; import java.util.Comparator; public class Demo {    public static void main(String[] args) {       ArrayListarrList = new ArrayList();       arrList.add(10);       arrList.add(50);       arrList.add(100);       arrList.add(150);       arrList.add(250);       arrList.add(100);       arrList.add(150);       arrList.add(250);       Comparator comparator = Collections.reverseOrder();       ... Read More

Suppose a date is given in LocalDate format, our task is to write a Java program that converts it into java.util.Date. For this problem, we need to add time information to the LocalDate by combining it with a time, such as midnight, or a timezone. Both LocalDate and java.util.Date classes are used to represent a date in Java. But, the LocalDate class, introduced with the release of Java8, represents a date without timezone information, whereas, the Date class is mutable and used for representing date and time with timezone. Let's understand the problem statement with an example. Example Scenario: Input: ... Read More

In this article, we will learn how to convert a LocalDateTime object to a java.util.Date object in Java. The conversion is essential when working with modern and legacy date/time APIs, ensuring compatibility between them. LocalDateTime Class The java.time.LocalDateTime class represents a specific date and time without including any time-zone details, following the ISO-8601 calendar system. For instance, it can represent values like 2007-12-03T10:15:30. This makes it ideal for scenarios where time-zone information is not required, focusing solely on the local date and time. Java Date class The java.util.Date class represents a specific moment in time, accurate to the ... Read More

In this article, we will learn to divide a number into smaller random ints in Java. Dividing a number into smaller random integers is a useful technique in various applications such as resource allocation, gaming, and randomization processes Divide a Number into Random Parts The approach relies on generating unique random dividers within the given number and then computing the differences between consecutive dividers to form the final parts.  Following are the steps to divide a number into smaller random ints in Java Create a HashSet to ... Read More

Heron’s formula gives the area of a triangle when the length of all three sides are already known.Let’s say we have the following three sides of a triangle −s1 = 15191235.0; s2 = 15191235.0; s3 = 1.01235479;Now, use the Heron’s formulae to find the area −area = (s1+s2+s3)/2.0d; resArea = Math.sqrt(area* (area - s1) * (area - s2) * (area - s3));Example Live Demopublic class Demo {    public static void main(String[] args) {       // sides of a triangle       double s1, s2, s3;       double area, resArea;       // three sides ... Read More

To convert integer array list to integer array is not a tedious task. First, create an integer array list and add some elements to it −ArrayList < Integer > arrList = new ArrayList < Integer > (); arrList.add(100); arrList.add(200); arrList.add(300); arrList.add(400); arrList.add(500);Now, assign each value of the integer array list to integer array. We used size() to get the size of the integer array list and placed the same size to the newly created integer array −final int[] arr = new int[arrList.size()]; int index = 0; for (final Integer value: arrList) {    arr[index++] = value; }Example Live Demoimport java.util.ArrayList; public ... Read More

To find all prime numbers up to any given limit, use the Sieve of Eratosthenes algorithm. At first we have set the value to be checked −int val = 30;Now, we have taken a boolean array with a length one more than the val −boolean[] isprime = new boolean[val + 1];Loop through val and set numbers as TRUE. Also, set 0 and 1 as false since both these number are not prime −isprime[0] = false; isprime[1] = false;Following is an example showing rest of the steps to get prime numbers using the Sieve of Eratosthenes algorithm −Example Live Demopublic class Demo ... Read More