Arrays in Java
An Array provides the ordered collection of objects. The members of an array can primitive data types or the objects of any class in Java. Arrays are implicit extensions of the Object class.
We can declare an Array, such as
We need to specify the size(fix size) of the array to create an array.
When an array is created each element is set to its default value like numeric types are set to 0, the char type is set to '\u0000', the boolean is set to false and the reference types are set to null.
We can create an array of arrays in Java(also known as multi-dimensional arrays), such as
For example,
Array
An Array provides the ordered collection of objects. The members of an array can primitive data types or the objects of any class in Java. Arrays are implicit extensions of the Object class.
We can declare an Array, such as
int arr1[]= {7,21,15,21,93,14,70};//Array Declaration int arr2[]=new int[15]; //Array Declaration int []arr3=new int[7]; //Array declaration
We need to specify the size(fix size) of the array to create an array.
Initializing an Array
When an array is created each element is set to its default value like numeric types are set to 0, the char type is set to '\u0000', the boolean is set to false and the reference types are set to null.
Advantages of Arrays
- Easy to use
- Efficient and fast
- indexed/random Access
Disadvantages of Arrays
- Fixed-size(static data structure)
public class ArrayTest { public static void main(String[] args) { int arr2[]=new int[15]; //Array Declaration for(int i=0;i<arr2.length;i++) { arr2[i]=(int)((Math.random())*99.9); } //Accessing Array for(int i=0;i<arr2.length;i++) { System.out.print(arr2[i]+"\t"); } } } Output: 54 20 84 7 54 25 88 43 87 44 95 79 40 60 33
Array of Objects
We can also create arrays of objects like primitive data types. For example
class Box{ // create a class int h,w,l; public Box(int h, int w, int l) {//Constructor super(); this.h = h; this.w = w; this.l = l; } public void displayVolume()//method to caculate volume { System.out.println("Volume "+ h*w*l); } } public class ArrayTest { public static void main(String[] args) { Box box[]=new Box[5];// create an Array of Boxes box[0]=new Box(10,21,13);//create five Boxes box[1]=new Box(11,19,44);//Add to Array box[] box[2]=new Box(21,17,26); box[3]=new Box(14,11,28); box[4]=new Box(17,22,19); for(Box b:box) { b.displayVolume(); } } } Output: Volume 2730 Volume 9196 Volume 9282 Volume 4312 Volume 7106
The array of Arrays OR multi-dimensional Arrays
We can create an array of arrays in Java(also known as multi-dimensional arrays), such as
double d[][]=new double[4][4]; int arr[][]=new int[4][];
The first or leftmost dimension of a multi-dimensional array must be specified, other dimensions can be left unspecified. Other dimensions may also vary in length.
int triangle[][]={ {1}, {1,1}, {1,2,1}, {1,3,3,1}, };
public class ArrayTest { public static void main(String[] args) { char c[][]= { //Multi-dimensional Arrays {'i'},{'l','o','v','e'},{'j','a','v','a'} }; //Accessing this array for(int i=0;i<c.length;i++) { for(int j=0;j<c[i].length;j++) { System.out.print(c[i][j]+"_"); } System.out.println(); } } } Output: i_ l_o_v_e_ j_a_v_a_