How to initialize an array in Java
In this tutorial, we will learn how to initialize a Java Array.
What is an Array in Java?
Arrays in Java are objects that can store elements of the same data type. In a Java Array, we can store only a fixed set of elements that can be accessed using indices.
Types of Arrays in Java
There are two types of Arrays in Java:
- Single-dimensional Array
- Multidimensional Array
Single Dimensional Array
Declaring a single-dimensional array
There are a couple of ways of declaring a single-dimensional array in java. You can do this using the following ways:
DataType[] arr; DataType arr[]; DataType []arr;
Example:
int a[]; int[] b; int []c;
Instantiating a single-dimensional array in Java
After declaring a single-dimensional array, to instantiate it we can use the following Syntax:
reference-variable = new DataType[size];
Example:
//one way of doing this is: int a[]; a = new int[5]; //or it can be done in a single line int b[] = new int[5];
Multidimensional Array
Declaring a Multidimensional array
Declaring of a multidimensional array can be done in the following ways:
DataType[][] reference-variable; DataType reference-variable[][]; DataType [][]reference-variable;
Example:
int[][] a; int b[][]; int [][]c;
Instantiating a Multidimensional array
Here is the syntax to instantiate a multidimensional array after declaring it:
reference-variable = new DataType[size][size];
Example:
//one way of doing this is: int a[][]; a = new int[3][4]; //or it can be done in a single line int b[][] = new int[3][4];
Initializing an array in Java
Single-dimensional
Here are the ways of initializing a single-dimensional array in java:
- We can declare, instantiate and initialize a single-dimensional array at the same time.
int a[] = {1,2,3,4,5};
- We can also initialize a single-dimensional array using indices.
a[0] = 1; a[1] = 2; a[2] = 3; a[3] = 4;
You can also do this using a for loop.
Multidimensional array
Next, you can initialize a multidimensional array in the following ways:
- Similar to a single-dimensional array you can initialize, instantiate and declare a multidimensional array at the same time.
int a[2][3] = {{1,2,3},{4,5,6}};
- We can also initialize a multidimensional array using indices. For example,
a[0][0] = 1; a[0][1] = 2; a[0][2] = 3; a[1][0] = 4; a[1][1] = 5; a[1][2] = 6;
You can also do this using a for loop.
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