java examples

public class Test { public static void main(String[] args) { String str = “Learn Java with alegrucoding.com”; String result = str.replaceAll(“\\s”, “”); System.out.println(result); } } Output: LearnJavawithalegrucoding.com import org.apache.commons.lang3.StringUtils; public class Test { public static void main(String[] args) { String str = “Learn Java with alegrucoding.com”; String result = StringUtils.deleteWhitespace(str); System.out.println(result); } } Output: LearnJavawithalegrucoding.com

Read More Remove all whitespaces from a String in Java

class PrintArrayElementsExample { public static void main(String[] args) { int[] arr1 = {1, 7, 9, 5, 2, 8, 3}; String[] arr2 = {“Megan”, “Tom”, “Melissa”, “John”, “Steve”}; // print elements of the arr1 System.out.println(Arrays.toString(arr1)); // print elements of the arr2 System.out.println(Arrays.toString(arr2)); } } Output: [1, 7, 9, 5, 2, 8, 3] [Megan, Tom, Melissa, John,…

Read More Print Array Elements in Java

public class SplitString { public static void main(String[] args) { String names = “Tom,Steve,John,Megan,Melissa”; // split string String[] arr = names.split(“,”); // print the size of the array System.out.println(arr.length); // print the elements Stream.of(arr).forEach(System.out::println); } } Output: 5 Tom Steve John Megan Melissa   If you need a list, instead of an array, use the…

Read More Split a comma-separated String in Java

In this post, you will learn how to Serialize and Deserialize an ArrayList in Java using the FileOutputStream and FileInputStream classes. How to Serialize an ArrayList in Java? Serialization is the process of changing the state of an object into a byte stream. For example, we use it to write some Java objects into a file.…

Read More Serialize and Deserialize an ArrayList in Java

Need to remove a character from String in Java?  You can do that by converting the String to a StringBuilder class and using the deleteCharAt() method that removes the character at a specified position. Example class Test { public static void main(String[] args) { String str = “Learn Java”; str = new StringBuilder(str).deleteCharAt(5).toString(); System.out.println(str); }…

Read More Remove a Character from String in Java

In one of the previous examples, we covered how to sort an ArrayList in ascending order. In this post, you will learn how to sort ArrayList in descending order in Java. We will explore the following ways: Using the sort() method Using the Collections.sort() and Collections.reverse() methods Sort ArrayList in descending order in Java using…

Read More Sort ArrayList in descending order in Java

Want to learn how to count character occurrences in Java String? Below is the program that uses a Map to store chars as keys and the number of occurrences as values. class Test { public static void main(String[] args) { String str = “moiujjmhrqdoasdsooqavvae”; Map<Character, Integer> map = new HashMap<>(); for (int i = 0;…

Read More Count Character occurrences in Java String

In this post, you will learn to check if a String contains only digits in Java. We will cover two methods: Using the Character.isDigit() method Using the Integer.parseInt() method Check if a String contains only digits in Java using the Character.isDigit() method In this example, we iterate over the elements (chars) of the String, and…

Read More Check if a String contains only digits in Java

We often need to compare two ArrayList in Java. In this post, you will learn how to do that in two ways: Using the ArrayList.equals() method Using the CollectionUtils.isEqualCollection() method Compare two ArrayList in Java using the ArrayList.equals() method The ArrayList.equals() method compares two ArrayList. It compares the sizes of the lists, elements equality, and…

Read More Compare two ArrayList in Java