Java create empty array

Check and Declare Empty Array in Java

A java empty array is an array that either consist of no elements or all the elements within the array are null . A java empty array can be declared using the new keyword. To check whether an array is empty or not in Java, we can check if its length is 0 or if all the elements in the array are null values. Also, Java provides different libraries to check java empty arrays.

Introduction

Empty array Java is referred to an array in java that has the length 0 or an array that has no elements.

To check if an array is empty in java it should be satisfying one of the following conditions:

• It should not contain any element, i.e. the size of the array should be 0 .
• It should be consisting only of null elements.

In further sections, we will learn how to declare a java empty array and how to check if an array is empty in java.

How to Check if An Array is Empty in Java?

Using Null Check

In this section, we will learn how to check for a java empty array using the NULL property. An array can be considered an empty array java if the array displays the value NULL .

Explanation of the Example:

In the above example, we have declared an array dates and assigned the values null . The ‘if condition’ will compare the dates with null . It if equals to null then our program will display «The input array is an empty array» otherwise it will display «The input array is not an empty array» .

Using Length Property

In this section, we will learn how to check for a java empty array using the length property. The length of an array can be used to determine whether it is an empty array or not. If the length of an array is 0 then the given array is an empty array.

Explanation of the example:

In the above example, we have declared an array dates . The dates.length will obtain the size of the array. Iif it equals 0 then our program will display «The input array is an empty array» otherwise it will display «The input array is not an empty array» .

Using Null Check on Elements

In this section, we will learn how to check for a java empty array using the null check on elements property. An array in java is said to be empty if all the elements present in the array are null . Thus we will traverse through the array and if we encounter a non-null element then the array is not empty otherwise it is empty.

Explanation of the example:

In the above example, we have declared an array dates and assigned the value null to each place in the array. The for condition Date it: dates will loop through each element in the dates and compare it with null . If any item does not equal to null then the boolean value isNotEmpty will be assigned true and we will break the loop. If isNotEmpty is false then our program will display «The input array is an empty array» otherwise it will display «The input array is not an empty array» .

Using the Java Library

In this section, we will learn how to check for a java empty array using the Java Library . Java has provided library methods to check if java empty array.

To check for empty array java we need to import the java.util.Arrays class in our Java program. The java.util.Arrays class provides the stream() method which can be used to call the allMatch() method to check the condition of all null values in the array.

Explanation of the example:

In the above example, we have declared an array dates and assigned the value null to each place in the array. The allMatch method will loop through each element in the dates and compare it with null . If any item does not equal null then the boolean value isEmpty will be assigned false and we will break the loop. If isEmpty is false then our program will display «The input array is an empty array» otherwise it will display «The input array is not an empty array» .

Using Apache Commons Library

In this section, we will learn how to check for a java empty array using the Apache commons library .

The isEmpty() function takes an array as a parameter. Then it will check if the parameter passed to it is null or empty. If the array passed as a parameter is null or empty then it would return a true . If the array passed as a parameter is not null or empty then it would return a false .

Note: If you’re using an external library like Apache Commons Lang, you need to make sure that you have added it to your project’s classpath. If the library is not available, you’ll get a «class not found» error.

Explanation of the example:

In the above example, we have declared an array dates and assigned the value null to each place in the array. The ArrayUtils.isEmpty(dates) method will loop through each element in the dates and compare it with null . If any item does not equal null then the boolean value isEmpty will be assigned false and we will break the loop. If isEmpty is false then our program will display «The input array is an empty array» otherwise it will display «The input array is not an empty array» .

How to Initialize an Empty Array in Java?

Using new Keyword

In this section, we will learn how to initialize empty array java using the new keyword.

To initialize an empty array java we need to use the new keyword followed by the data type of the elements the array would store. The size of this array will be 0 .

Using new Keyword with Predefined Size

In the previous section, we defined a java empty array of size 0 . But what if we want to declare a java array of a certain size?

The new keyword can be used to initialize an array java with a predefined size. To initialize an array java with a predefined size we need to use the new keyword followed by the data type of the array and the size of the array.

Conclusion

• An array is said to be empty in java if it has size 0.
• An array is said to be empty in java if it displays a null value.
• An empty array java can be initialized using the new keyword.

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Initialize an Empty Array in Java

1. new Keyword to Declare an Empty Array in Java
2. Declare of an Empty Array Using new Keyword With Predefined Size
3. Initialize an Array Without Using new Keyword

This tutorial article will introduce how to initialize an empty array in Java.

There are several ways to declare an array in Java, but we can only do this dynamically.

new Keyword to Declare an Empty Array in Java

The new keyword initiates an object dynamically (runtime allocation of memory), and returns the reference of that object’s memory.

To declare an empty array in Java, we can use the new keyword. After the declaration of an empty array, we can initialize it using different ways.

The syntax of declaring an empty array is as follows.

data-type[] array-name = new data-type[size]; //or  data-type array-name[] = new data-type[size]; 

There are two major ways to declare an empty array in Java using the new keyword that is as follows.

Declare of an Empty Array Using new Keyword With Predefined Size

We can declare an empty array using the new keyword with a predefined size. In this case, we will provide the size to the array before runtime, and then the array will be declared according to the size.

The example code of the declaration of an empty array by predefined size in Java and then initialize that array’s values are as follows.

public class Declare_Empty_Array   public static void main(String args[])   int Size = 5;  int array[] =new int[Size];  for(int i=0;iSize;i++)    array[i] = i+1;  System.out.println("The value stored in array on index "+i+" is: "+array[i]);  >  > > 

In this above code, we declare an empty array with a predefined size and then initialize that array’s values using the for loop. We can also use the while loop for the same purpose.

The output of the code is as follows.

The value stored in the array on index 0 is: 1 The value stored in the array on index 1 is: 2 The value stored in the array on index 2 is: 3 The value stored in the array on index 3 is: 4 The value stored in the array on index 4 is: 5 

Initialize an Array Without Using new Keyword

There is another way to initialize an array and then update its values without using the new keyword. In this method, we can initialize the array with predefined values and update them with our desired values.

import java.util.Scanner; public class Declare_Empty_Array   public static void main(String args[])   int array[] = 5, 5, 5, 5, 5>;  for(int i=0;iarray.length;i++)    array[i] = i+1;  System.out.println("The value updated in array on index "+i+" is: "+array[i]);  >  > > 

In the above code, we initialize an array that has 5 stored in it initially, and after that, we can update its values.

The output of the code is as follows.

The value updated in array on index 0 is: 1 The value updated in array on index 1 is: 2 The value updated in array on index 2 is: 3 The value updated in array on index 3 is: 4 The value updated in array on index 4 is: 5 

Related Article — Java Array

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How to Initialize an Empty Array in Java

In Java, an array is automatically considered an object, and memory is allocated to them dynamically. Array declaration, initialization, and instantiation are three different things in Java. Array declaration means declaring an array of any data type with a specific name which tells the compiler that there is an array. Array instantiation means instantiating an object of an array, while initialization means assigning values to the array.

This post will illustrate the method to initialize an empty array in Java.

How to Initialize an Empty Array in Java?

Empty array initialization refers to the process of assigning values by declaring an array of a specific size without giving it any values. The array will, by default, contain garbage values, called random values, if it is not initialized with any data.

Let’s first understand the difference between declaration, instantiation, and initialization with examples.

Array Declaration

An array is simply a data structure that may hold a number of elements next to one another:

Here, “int” is the data type of an array, and the “arr” is the name of the array.

Array Instantiation

When we say “instantiate an array“, it means that we are giving that array some space in memory. You may know that in Java, the “new” keyword is used to instantiate objects as follows:

Here, “10” is the size of an array named “arr” which will now have ten consecutive empty memory blocks.

Array Initialization

Array initialization means assigning the values and storing it the specified indexes:

Let’s initialize the empty array with examples.

How to Initialize an Empty Array in Java by Using the “new” Keyword?

This section will first declare and instantiate an array without assigning any value (creating an empty array). Then, we will initialize this empty array with some specific values.

There are two syntax formats that can be utilized for declaring and instantiating an empty array.

The size or the length of the array is defined in rectangular brackets on the right side. The size tells the compiler how much space should be reserved for the array.

Example 1: Declare an Empty Array

In this example, we will declare and instantiate an integer type empty array of size “5”:

This array reserves five empty blocks in the memory that will be used later. At the time of an empty array declaration, the array is typically initialized with garbage values of the same data type that will be overwritten when we assign the values to it.

Then, we will verify the array length using the “arr.length” property:

We will print the array “arr” by using a “for” loop. As we have not initialized array, so currently the array comprises garbage values:

Since “arr” is not initialized, its five memory blocks comprise “0” as the garbage value:

Example 2: Initialize an Empty Array

In this example, we will initialize the above created empty array by assigning values to it using “for” loop:

for ( int i = 0 ; i < 5 ; i ++ )
{
arr [ i ] = i + 1 ;
System . out . println ( «The value at index » + i + » is: » + arr [ i ] ) ;
}

The output shows the length of the array that is “5” and the predefined values:

We presented the method to initialize an empty array in Java.

Conclusion

To initialize an empty array in Java, you must first declare and instantiate an array with some specific size. When you declare and instantiate an array, the array will reserve some space in memory based on the defined size. This array will, by default, contain garbage values. Initializing an empty array means assigning values to the empty declared array. This post illustrated the methods to initialize an empty array in Java.

About the author

Farah Batool

I completed my master’s degree in computer science. I am an academic researcher and love to learn and write about new technologies. I am passionate about writing and sharing my experience with the world.

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