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type array_var[];In above syntax, type declares the base type of the array. what type of data the array will hold.
int employee_id[];In above code, employee_id is the array variable, but here no array will be created, only null is set to employee_id(An array with no value).
array_var = new type[size];
here type specifies the type of data being allocated, size specifies the number of elements in the array. array_var is the array variable that is linked to the variable.
employee_id = new int[12];employee_id is the integer array which will have 12 integers. All elements in this array are initialized to 0.
employee_id[2] = 1002;here 1002 value is assigned to 3rd element in the array since array index starts at 0. To print 3rd element in the array.
System.out.println(employee_id[2]);Example:
// Array one dimensional sample code. class ArrayOneDimensionTest { public static void main(String args[]) { // declares integer one dimensional array int employee_id[]; // allocates memory for integer array which will have 5 elements. employee_id = new int[5]; //initializes value to array indexes. employee_id[0] = 1001; employee_id[1] = 1002; employee_id[2] = 1003; employee_id[3] = 1004; employee_id[4] = 1005; //prints 4th employee id in the employee_id array. System.out.println("4th Employee id is:" + employee_id[3]); } }Output:
4th Employee id is:1004We can also declare, allocate memory and length in the single line as below
int employee_id = new int[5];Arrays can be initialized in declaration itself as below.
int employee_id[] = {1001, 1002, 1003, 1004, 1005};integer array will be created with 5 elements and assigned employee_id array variable.
// Array one dimensional sample code. class ArrayOneDimensionTest1 { public static void main(String args[]) { // declares integer one dimensional array and initializes data int employee_id[] = {1001, 1002, 1003, 1004, 1005}; //prints 4th employee id in the employee_id array. System.out.println("4th Employee id is:" + employee_id[3]); } }Output:
4th Employee id is:1004
type[] variable_name;Example:
int a[] = new int[5]; int[] a = new int[5];
// Array one dimensional sample code. class ArrayOneDimensionTest2 { public static void main(String args[]) { // declares integer one dimensional array int employee_id[] = {1001, 1002, 1003, 1004, 1005}; //prints all employee id in the array. for(int i=0; i<5; i++) { System.out.println("Employee id[" + i +"] is:" + employee_id[i]); } } }Output:
Employee id[0] is:1001 Employee id[1] is:1002 Employee id[2] is:1003 Employee id[3] is:1004 Employee id[4] is:1005
int matrix[][] = new int[5][5]; //alternate way to declare and allocate memory and size. //int[][] matrix = new int[5][5];Two dimensional array matrix example:
// Array two dimensional sample code. class TwoDimensionalArrayTest { public static void main(String args[]) { // declares two dimensional array and allocates memory and size int matrix[][] = new int[3][5]; int val = 0; //initializes value in array of array elements. for(int i=0; i<3; i++) { for(int j=0; j<5; j++) { matrix[i][j] = val; val = val + 1; } } //prints all elements in array of arrays for(int i=0; i<3; i++) { for(int j=0; j<5; j++) { System.out.print(matrix[i][j] + " "); } System.out.println(); } } }Output:
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