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Java String.charAt() The method charAt() returns the character at the specified index. The index value must be between 0 and String.length() – 1. Available Signatures [source,java,gutter:,false] public char charAt(int index) Example [source,java,gutter:,true] @Test public void whenCallCharAt_thenCorrect() { assertEquals(‘P’, “Paul”.charAt(0)); } Throws * IndexOutOfBoundsException – if a non-existent or a negative… Continue Reading char-at
The State of Java in 2019 I’ve been running the yearly 2019 “State of Java” survey for the last couple of weeks. In its 6th year, we had 6707 developers taking the time to go through and answer; if that was you – thank you! Time for the results ?… Continue Reading java-in-2019
Java Scanner hasNext() vs. hasNextLine() 1. Overview The Scanner class is a handy tool that can parse primitive types and strings using regular expressions and was introduced into the java.util package in Java 5. In this short tutorial, we’ll talk about its hasNext() and hasNextLine() methods. Even though these two… Continue Reading java-scanner-hasnext-vs-hasnextline
Validations for Enum Types 1. Introduction In the tutorial Java Bean Validation Basics, we saw how we can apply javax validations using JSR 380 to various types. And in the tutorial Spring MVC Custom Validation, we saw how to create custom validations. In this next tutorial, we’ll focus on building validations for… Continue Reading javax-validations-enums
Defensive Copies for Collections Using AutoValue 1. Overview Creating immutable value objects introduces a bit of unwanted boilerplate. Also, Java’s standard collections types have the potential to introduce mutability to value objects where this trait is undesirable. In this tutorial, we’ll demonstrate how to create defensive copies of collections when… Continue Reading autovalue-defensive-copies
Digital Signatures in Java 1. Overview In this tutorial, we’re going to learn about the Digital Signature mechanism and how we can implement it using the Java Cryptography Architecture (JCA). We’ll explore the KeyPair, MessageDigest, Cipher, KeyStore, Certificate, and Signature JCA APIs. We’ll start by understanding what is Digital Signature,… Continue Reading java-digital-signature
How to Determine if a Binary Tree is Balanced 1. Overview Trees are one of the most important data structures in computer science. We’re usually interested in a balanced tree, because of its valuable properties. Their structure allows performing operations like queries, insertions, deletions in logarithmic time. In this tutorial,… Continue Reading java-balanced-binary-tree
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Knapsack Problem Implementation in Java 1. Introduction The knapsack problem is a combinatorial optimization problem that has many applications. In this tutorial, we’ll solve this problem in Java. 2. The Knapsack Problem In the knapsack problem, we have a set of items. Each item has a weight and a worth… Continue Reading java-knapsack
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Intro to the Java SecurityManager 1. Overview In this tutorial, we’ll have a look into Java’s built-in security infrastructure, which is disabled by default. Specifically, we’ll examine its main components, extension points, and configurations. 2. SecurityManager in Action It might be a surprise, but default SecurityManager settings disallow many standard operations:… Continue Reading java-security-manager
Grouping Javax Validation Constraints 1. Introduction In our Java Bean Validation Basics tutorial, we saw the usage of various built-in javax.validation constraints. In this tutorial, we’ll see how to group javax.validation constraints. 2. Use Case There are many scenarios where we need to apply constraints on a certain set of… Continue Reading javax-validation-groups