6 ways to declare and initialize a two-dimensional (2D) String and Integer Array in Java - Example Tutorial

Declaring a two-dimensional array is very interesting in Java as the Java programming language provides many ways to declare a 2D array and each one of them has some special things to learn about. For example, It's possible to create a two-dimensional array in Java without specifying the second dimension, sounds crazy right? but it's possible because a two-dimensional array in Java is nothing but an array of array. You can even create a two-dimensional array where each subarray has a different length or different type, also known as a heterogeneous array in Java. This means it's possible to create a two-dimensional array with variable column length in Java.

Recursive Binary Search Algorithm in Java - Example Tutorial

The binary search algorithm is one of the most famous search algorithms in computer science. It allows you to search a value in logarithmic time i.e. O(logN), which makes it ideal to search a number on a huge list. For example, in order to search a number in a list of 1 million numbers will take around 210 comparisons compared to 1 million comparisons required by the linear search algorithm. The only thing is that the list must be sorted before you can use a binary search algorithm and it must support index-based search. That's why binary search is often implemented using an array because doing a binary search with a linked list will not be fast because it doesn't provide index-based access i.e. O(1) access. You have to traverse to that element to read its value in the linked list which is O(n), effectively reducing the performance of binary search to a sequential search algorithm.

3 Ways to Convert an Array to ArrayList in Java? Example

How to convert an Array to ArrayList in Java
Have you encountered any situation where you quickly wanted to convert your array to ArrayList or ArrayList to array in Java? I have faced many such situations that motivate me to write these quick Java tips about converting an array to ArrayList and ArrayList to array in Java. Both array and ArrayList are quite common and every Java developer is familiar with this. Former is used to store objects and primitive types while later can only hold objects. The array is part of standard Java fundamental data structure while ArrayList is part of the collection framework in Java.

Difference Between Linked List and Array in Java? Example

Array and linked lists are two fundamental data structures in the programming world. Almost all programs use Array in some form or other, which makes it increasingly important to learn array and linked list. The difference between the linked list and array data structure is also a popular data structure question, frequently asked in the various programming job interviews. This makes it even more important to learn and understand the difference between an array and a linked list. Well, there are a lot of differences between these two starting from how they store data, to how you retrieve data from them.

How to Convert Byte Array to InputStream and OutputStream in Java? Example

Are you stuck with your coding because you have a byte array and the next method in the chain needs an InputStream? don't worry Java has a solution for that, You can use ByteArrayInputStream to convert byte array to InputStream in Java. This class takes a byte array as the source and since it's a subclass of InputStream, you can easily pass this to any method, which accepts InputStream as a parameter. Though most of the API like JDBC and File API allows you to read directly from InputStream because this allows you to process an arbitrary content with limited heap space. You should take advantage of this and directly read from InputStream instead of getting byte array and then converting them back to InputStream.

How to Convert InputStream to Byte Array in Java - 2 Examples

Sometimes we need to convert InputStream to byte array in Java, or you can say reading InputStream as a byte array, In order to pass output to a method that accepts byte array rather than InputStream. One popular example of this, I have seen is an older version of Apache commons-codec, while converting byte array to the hex string. Though, a later version of the same library does provide an overloaded method, to accept InputStream. Java File API provides excellent support to read files like image, text as InputStream in Java program, but as I said, sometimes you need String or byte array, instead of InputStream .

How to Reverse Array in Place in Java? Solution With Explanation

Reversing an array sounds pretty easy, isn't it? It does sound like that, because all you need to do is create an array of the same size, iterate through the original array from end to start, and populate your new array. Boom!!, you have got an array that has elements in reverse order of the original array, but the problem is you have used an additional array here, which makes space complexity of your solution O(n). You cannot use this solution if the array is big e.g. an array of 10 million orders and you don't have enough heap space available.

How to Convert List of Integers to Int Array in Java - Example

So, you have a List of Integers and you want to convert them into int array? Yes, you read it write, not on Integer array but int array. Though in most practical purpose, Integer array can be used in place of int[] because of autoboxing in Java, you still need an int[] if your method accepts it. In Java, you can not typecast an Integer array into an int array. Many Java programmer think about toArray() method from java.util.List to convert a List into Array, but unfortunately, toArray() is useless most of the time. It doesn't allow you to convert List into primitive arrays.

Can You Make an Array or ArrayList Volatile in Java?

This is one of the many interesting multi-threading questions I have shared in my post 50 multi-threading interview questions. Yes, you can make an array volatile in Java, there is no problem with that, neither compiler will flag any error not JVM will throw any exception but the tricky part is why you want to make an array volatile and what is the effect of making an array volatile in Java? In order to answer this question, you must be familiar with both volatile modifier and Java memory model, otherwise, it would be difficult to answer, and that's why it's also one of the trick questions from Java interviews.

How to declare and initialize a List with values in Java (ArrayList/LinkedList) - Arrays.asList() Example

Hello guys, today, I am going to share with you a useful tip to initialize a List like ArrayList or LinkedList with values, which will help you a lot while writing unit tests and prototypes. Initializing a list while declaring is very convenient for quick use, but unfortunately, Java doesn't provide any programming constructs like the collection literals of Scala, but there is a trick which you can use to declare and initialize a List at the same time. This trick is also known as initializing a List with values. I have used this trick a lot while declaring list for unit testing and writing demo programs to understand an API etc and today I'll you'll also learn that.

How to find the largest and smallest number in given Array in Java

Hello guys, today I am going to discuss one of the frequently asked programming interview questions to find the largest and smallest number from an integer array. This question is commonly asked on telephonic interviews and the first round for screening candidates. This coding problem is in the same league of other frequently asked algorithmic questions like Fibonacci, Palindrome, Prime, and Power of two checks. They are easy but you will find them difficult during the interview because of the pressure, particularly if you have not solved them before. Sometimes even if you have solved the problem one time, you tend to do mistakes because you haven't understood them properly. So, always take your time to understand the question.

How to Find Multiple Missing Integers in Given Array of Numbers with Duplicates in Java?

Hello guys, It's been a long time since I have discussed any coding or algorithm interview questions, so I thought to revisit one of the most popular array-based coding problems of finding missing numbers in a given array of integers. You might have heard or seen this problem before on your programming job interviews and you might already know how to solve this problem. But, there are a lot of different versions of this problem with increasing difficulty levels which interviewers normally use to confuse candidates and further test their ability to adapt to frequent changes, which is key to surviving in the ever-changing software development world.