Single Dimensional(1D) Arrays in java

The simplest form of an array is a single dimensional array.


Syntax to Declare an Array in java

Syntax :


dataType[]  name ; (or)  
dataType  []name ; (or)  
dataType  name[];  

Instantiation of an Array in java


arrayNam= new DataType [ size ] ;

Declaration and Instantiation of an Array at the same time.


int a[]=new int[5];
int[] a=new int[5];
int a[]=new int[5];

We are creating int type array of size=5.

Example of single dimensional array

Let's see the simple example of java array, where we are going to declare, instantiate, initialize and traverse an array.

//example of 1D array
class Example
{
	public static void main(String[] args) {
	//declearing and instantiating int type array
	int[] a=new int[5];

	//initializing the elements of array
	a[0]=45;//first element
	a[1]=54;
	a[2]=465;
	a[3]=32;
	a[4]=55;//last element

	//now going to traverse the elements of array
	 for(int i=0;i<5;i++)
	 {
	 	System.out.println("a["+i+"] = "+a[i]);
	 }
	}
}
a[0] = 45
a[1] = 54
a[2] = 465
a[3] = 32
a[4] = 55

Example of Initializing the elements of an array at the time of declaring the array.


//example of 1D array
class Example {

    public static void main(String[] args) {
        /*if we know the values in advance then we can initialize the elements at the time of declearing the array.
         */
        int a[] = {12, 32, 54, 65, 67};

        //now going to traverse the elements of array
        int size = a.length;//fetching the size of array
        for (int i = 0; i < size; i++) {
            System.out.println("a[" + i + "] = " + a[i]);
        }
    }
}
a[0] = 12
a[1] = 32
a[2] = 54
a[3] = 65
a[4] = 67

In this case, we don't have to give the size explicitly. size=number of elements given.

Program to read marks of 5 students and store them under an array.

//example of reading values from user and putting to array
import java.util.Scanner;
class Example {

    public static void main(String[] args) {
        int marks[]=new int[5];
        //taking input from user and store in array
        Scanner ob=new Scanner(System.in);
        for (int i = 0; i < marks.length; i++) {
            marks[i]=ob.nextInt();
        }        
        //traversing elements of array
        for (int i = 0; i < marks.length; i++) {
            System.out.println("mark of student "+(i+1)+" is "+marks[i]);
        }
    }
}
34 40 54 34 45
mark of student 1 is 34
mark of student 2 is 40
mark of student 3 is 54
mark of student 4 is 34
mark of student 5 is 45

Program to take 5 elements from the user and sum them.
//finding the sum of elements of array
import java.util.Scanner;

class Example {

    public static void main(String[] args) {
        int marks[] = new int[5];
        //taking input from user and store in array
        Scanner ob = new Scanner(System.in);
        for (int i = 0; i < marks.length; i++) {
            marks[i] = ob.nextInt();
        }

        int sum = 0;
        //adding elements one by one
        for (int i = 0; i < marks.length; i++) {
            sum = sum + marks[i];
        }
        System.out.println("Sum of elements = " + sum);
    }
}
3 4 3 5 6 
Sum of elements = 21

Example of Passing Array to method in java

//example of passing array to method as prameter
// in this example we reverse the elements of array 
import java.util.Scanner;

class Example {

    public void reverse(int a[]) {
        //we are going to traverse the elements in opposite direct 
        // size-1 to 0
        int size = a.length;
        for (int i = size - 1; i >= 0; i--) {
            System.out.print(a[i] + "\t");
        }
    }

    public static void main(String[] args) {
        int []myarray={1,3,4,5};
        
        /*since the reverse() method is non-static ,we need to create 
        the object of Example class to call the reverse() method  */
        Example e=new Example();
        e.reverse(myarray);//pass myarray as parameter
    }

}
5	4	3	1