Zak Dyer

Zak Dyer

1593847285

How to Convert an Array to an ArrayList in Java

In this tutorial, we’ll be converting an array into a more versatile ArrayList in Java.

  • Arrays.asList()
  • new ArrayList<>(Arrays.asList()) (Most popular and used approach)
  • new ArrayList<>(List.of())
  • Collections.addAll()
  • Collectors.toList()
  • Collectors.toCollection()
  • Lists.newArrayList()

Arrays are simple and provide the basic functionality of grouping together a collection of objects or primitive data types. However, arrays are also limited - their size is fixed and even basic operations like adding new items at the beginning or rearranging elements can get complicated.

Thankfully, the Collections Framework introduced us to many very useful implementations of Lists, Sets, and Queues.

One of these is the ArrayList, a really versatile and popular implementation of a List.

An ArrayList’s constructor will accept any Collection. We can get creative with the type of collection we pass into it.

#java #developer

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How to Convert an Array to an ArrayList in Java
Tyrique  Littel

Tyrique Littel

1600135200

How to Install OpenJDK 11 on CentOS 8

What is OpenJDK?

OpenJDk or Open Java Development Kit is a free, open-source framework of the Java Platform, Standard Edition (or Java SE). It contains the virtual machine, the Java Class Library, and the Java compiler. The difference between the Oracle OpenJDK and Oracle JDK is that OpenJDK is a source code reference point for the open-source model. Simultaneously, the Oracle JDK is a continuation or advanced model of the OpenJDK, which is not open source and requires a license to use.

In this article, we will be installing OpenJDK on Centos 8.

#tutorials #alternatives #centos #centos 8 #configuration #dnf #frameworks #java #java development kit #java ee #java environment variables #java framework #java jdk #java jre #java platform #java sdk #java se #jdk #jre #open java development kit #open source #openjdk #openjdk 11 #openjdk 8 #openjdk runtime environment

Joseph  Murray

Joseph Murray

1623911281

How to Print an Array in Java

Introduction

Printing an array is a quick way to give us visibility on the values of the contents inside. Sometimes the array values are the desired output of the program.

In this article, we’ll take a look at how to print an array in Java using four different ways.

While the “best way” depends on what your program needs to do, we begin with the simplest method for printing and then show more verbose ways to do it.

#java #array #how to print an array in java #array in java #print an array in java #print

Samanta  Moore

Samanta Moore

1620458875

Going Beyond Java 8: Local Variable Type Inference (var) - DZone Java

According to some surveys, such as JetBrains’s great survey, Java 8 is currently the most used version of Java, despite being a 2014 release.

What you are reading is one in a series of articles titled ‘Going beyond Java 8,’ inspired by the contents of my book, Java for Aliens. These articles will guide you step-by-step through the most important features introduced to the language, starting from version 9. The aim is to make you aware of how important it is to move forward from Java 8, explaining the enormous advantages that the latest versions of the language offer.

In this article, we will talk about the most important new feature introduced with Java 10. Officially called local variable type inference, this feature is better known as the **introduction of the word **var. Despite the complicated name, it is actually quite a simple feature to use. However, some observations need to be made before we can see the impact that the introduction of the word var has on other pre-existing characteristics.

#java #java 11 #java 10 #java 12 #var #java 14 #java 13 #java 15 #verbosity

Joseph  Murray

Joseph Murray

1624070700

How to Declare and Initialize an Array in Java

Introduction

In this tutorial, we’ll take a look at how to declare and initialize arrays in Java.

We declare an array in Java as we do other variables, by providing a type and name:

int[] myArray;

To initialize or instantiate an array as we declare it, meaning we assign values as when we create the array, we can use the following shorthand syntax:

int[] myArray = {13, 14, 15};

Or, you could generate a stream of values and assign it back to the array:

int[] intArray = IntStream.range(1, 11).toArray();
int[] intArray = IntStream.rangeClosed(1, 10).toArray();
int[] intArray = IntStream.of(1, 2, 3, 4, 5, 6, 7, 8, 9, 10).toArray();

To understand how this works, read more to learn the ins and outs of array declaration and instantiation!

#java #how to declare and initialize an array in java #array in java #assign #declare #declare and initialize an array in java

Wilford  Pagac

Wilford Pagac

1595517480

How to Convert a Java Array to ArrayList

Introduction

In this tutorial, we’ll be converting an array into a more versatile ArrayList in Java.

Arrays are simple and provide the basic functionality of grouping together a collection of objects or primitive data types. However, arrays are also limited - their size is fixed and even basic operations like adding new items at the beginning or rearranging elements can get complicated.

Thankfully, the Collections Framework introduced us to many very useful implementations of Lists, Sets, and Queues.

One of these is the ArrayList, a really versatile and popular implementation of a List.

An ArrayList’s constructor will accept any Collection. We can get creative with the type of collection we pass into it.

Arrays.asList()

Let’s start off with the simplest form of conversion. The Arrays helper class has a lot of useful methods. The asList() method returns the contents of the array in a List:

Employee emp1 = new Employee("John");
Employee emp2 = new Employee("Sarah");
Employee emp3 = new Employee("Lily");

Employee[] array = new Employee[]{emp1, emp2, emp3};

List<Employee> list = Arrays.asList(array);
System.out.println(list);

This will result in a List implementation (ArrayList) to be populated with emp1emp2 and emp3. Running this code results in:

[Employee{name='John'}, Employee{name='Sarah'}, Employee{name='Lily'}]

new ArrayList<>(Arrays.asList())

A better approach than just assigning the return value of the helper method is to pass the return value into a new ArrayList<>()This is the standard approach used by most people.

This is because the asList() method is backed by the original array.

If you change the original array, the list will change as well. Also, _asList()_ returns a fixed size, since it’s backed by the fixed array. Operations that would expand or shrink the list would return a _UnsupportedOperationException_.

To avoid these, we’ll apply the features of an ArrayList by passing the returned value of asList() to the constructor:

Employee[] array = new Employee[]{emp1, emp2, emp3};

List<Employee> list = new ArrayList<>(Arrays.asList(array));
System.out.println(list);

This results in:

[Employee{name='John'}, Employee{name='Sarah'}, Employee{name='Lily'}]

new ArrayList<>(List.of())

Since Java 9, you can skip initializing an array itself and passing it down into the constructor. You can use List.of() and pass individual elements:

List<Employee> list = new ArrayList<>(List.of(emp1, emp2, emp3));
System.out.println(list);

This results in:

[Employee{name='John'}, Employee{name='Sarah'}, Employee{name='Lily'}]

Collections.addAll()

The Collections class offers a myriad of useful helper methods and amongst them is the addAll() method. It accepts a Collection and a vararg of elements and joins them up.

It’s very versatile and can be used with many collection/vararg flavors. We’re using an ArrayList and an array:

Employee[] array = new Employee[]{emp1, emp2, emp3};
List<Employee> list = new ArrayList<>();

Collections.addAll(list, array);
System.out.println(list);

This results in:

[Employee{name='John'}, Employee{name='Sarah'}, Employee{name='Lily'}]

#java #javascript #code #arrays #arraylist