An array stores a fixed-size sequential collection of elements of the same type. An array is used to store a collection of data, but it is often more useful to think of an array as a collection of variables of the same type. A specific element in an array is accessed by its index. Arrays offer a convenient means of grouping related information. Indexing in and array starts at 0 to n-1 where n is the length of array
To use an array in a program, you must declare a variable to reference the array, and you must specify the type of array the variable can reference.
public class ArrayExample{
public static void main(String[] args){
// Creating an array
int[] arr = {1, 2, 3, 4, 5};
//accessing values by index
System.out.println(arr[4]);
}
}5
public class ArrayExample{
public static void main(String[] args){
// declaring a reference for int array
int[] integerArray;
// creating array of size 5
// this array will be able to store 5 values
integerArray = new int[5];
// assigning values
integerArray[0] = 5;
integerArray[1] = 10;
integerArray[2] = 15;
integerArray[3] = 20;
integerArray[4] = 25;
// getting length of the array
int len = integerArray.length;
for(int i=0; i<len; i++){
System.out.println(integerArray[i]);
}
}
}5
10
15
20
25
Alternatively Arrays can also be created as
int integerArray[] = new int[5];both are valid ways of creating arrays
In Java, multidimensional arrays are actually arrays of arrays. These, as you might expect, look and act like regular multidimensional arrays. However, as you will see, there are a couple of subtle differences. To declare a multidimensional array variable, specify each additional index using another set of square brackets. For example, the following declares a twodimensional array variable called twoD:
int[][] twoD = new int[4][5];This allocates a 4 by 5 array and assigns it to twoD. Internally, this matrix is implemented as an array of arrays of int. Conceptually, this array will look like the one shown in Figure 3-1. The following program numbers each element in the array from left to right, top to bottom, and then displays these values:
// Demonstrate a two-dimensional array.
class TwoDArray {
public static void main(String args[]) {
int twoD[][]= new int[4][5];
int i, j, k = 0;
for(i=0; i<4; i++){
for(j=0; j<5; j++) {
twoD[i][j] = k;
k++;
}
}
for(i=0; i<4; i++) {
for(j=0; j<5; j++){
System.out.print(twoD[i][j] + " ");
}
System.out.println();
}
}
}0 1 2 3 4
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public class TwoDArray{
public static void main(String[] args){
int[][] intArray = {
{'1', '2', '3'},
{'2', '3', '4'}
};
int i, j;
for(i=0; i<2; i++){
for(j=0; j<3; j++){
System.out.print(intArray[i][j] + " ");
}
System.out.println();
}
}
}1 2 3
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