java examples

public class Test { public static void main(String[] args) { Integer[] array = new Integer[]{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}; // reverse an array Integer[] reversedArray = reverse(array); // print the elements Arrays.stream(reversedArray).forEach(item -> System.out.print(item + ” “)); } public static Integer[] reverse(Integer[] array) { List arrayList = Arrays.asList(array); Collections.reverse(arrayList); return…

Read More Reverse an Array in Java

import java.util.*; public class Test { public static void main(String[] args) { Map<String, String> map = new HashMap<>(); map.put(“New York”, “city”); map.put(“Japan”, “country”); map.put(“London”, “country”); map.put(“Boston”, “city”); // update the value of “London” to “city” map.replace(“London”, “city”); System.out.println(map); } } Output: {New York=city, Japan=country, London=city, Boston=city} public class Test { public static void main(String[] args)…

Read More Java – Change the value of a key in a HashMap

public class Test { public static void main(String[] args) { Map<String, Integer> map = new HashMap<>(); map.put(“one”, 1); map.put(“two”, 2); map.put(“three”, 3); map.put(“four”, 4); // modify the key “two” map.remove(“two”); map.put(“twoUpdated”, 2); System.out.println(map); } } Output: {four=4, one=1, twoUpdated=2, three=3} public class Test { public static void main(String[] args) { Map<String, Integer> map = new…

Read More Java – Update the Key in a HashMap

public Object get(int index); import java.util.*; public class Test { public static void main(String[] args) { List<String> cities = new ArrayList<>(Arrays.asList(“New York”, “London”, “Paris”, “Chicago”, “Rome”)); // retrieve the second element from the list System.out.println(cities.get(2)); // retrieve the 4th element from the list System.out.println(cities.get(4)); } } Output: Paris Rome   Lists are zero-based indexes, which means that the…

Read More Get the Element from an ArrayList in Java

import java.util.*; public class Test { public static void main(String[] args) { List<String> names = new ArrayList<>(Arrays.asList(“Megan”, “Tom”, “Steve”, “Megan”, “Meliisa”, “Tom”, “John”)); Set<String> uniqueNames = new HashSet<>(names); // creating a Set from the List System.out.println(uniqueNames); } } Output: [Megan, Tom, Steve, John, Meliisa] Remove duplicates from a List in Java using the Java 8…

Read More Remove Duplicates from a List in Java

import java.util.*; public class Test { public static void main(String[] args) { List<Integer> numbers = new ArrayList<>(Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)); System.out.println(numbers.stream().mapToInt(Integer::intValue).average().getAsDouble()); } } Output: 5.5   Here, we used the mapToInt(Integer::intValue) to convert the Stream<Integer> which is the result of the stream() method, to IntStream. import java.util.*; public class…

Read More Find the Average of Numbers in Java

public class Test { public static void main(String[] args) { int[] array = new int[]{7, 1, 9, 2, 5}; Arrays.sort(array); Arrays.stream(array).forEach(System.out::print); } } Output: 1 2 5 7 9   Note: values of type int will be automatically converted to the corresponding Wrapper class. And since the Integer Wrapper class implements Comparable, we can sort…

Read More Sort an Array in Java

import java.util.*; public class Test { public static void main(String[] args) { List<Integer> numbers = new ArrayList<>(Arrays.asList(7, 12, 5, 28, 97, 14, 2, 7, 8, 12, 19, 22)); Collections.sort(numbers); System.out.println(numbers); } } Output: [2, 5, 7, 7, 8, 12, 12, 14, 19, 22, 28, 97] Using the sort() method from ArrayList class public class Test…

Read More Sort a List in Java

class Test { public static void main(String[] args) { Map<Integer, String> map = new HashMap<>(); map.put(1, “Java”); map.put(7, “Python”); map.put(10, “Ruby”); map.put(3, “Kotlin”); for (Map.Entry<Integer, String> entry : map.entrySet()) { System.out.println(“Key = ” + entry.getKey() + “, Value = ” + entry.getValue()); } } } Output: Key = 1, Value = Java Key = 3,…

Read More Iterate over a Map in Java

public class Test { public static void main(String[] args) { int num = 8; int num2 = 9; if(num % 2 == 0) { System.out.println(“num is an even number!”); } else { System.out.println(“num is odd number!”); } if(num2 % 2 == 0) { System.out.println(“num2 is an even number!”); } else { System.out.println(“num2 is odd number!”);…

Read More Check if the Number is Even or Odd in Java