In this chapter you will learn:

1. What is an Array?
2. Single Dimensional Array vs. Multi-Dimensional Array
3. How to pass an array to method
4. Array Class and Manipulation

What is an array?

An array is a collection of data of same data type. It is like a container object which holds fixed number of same type value. The size of array is defined when initialized array. The item stored in array is called element and each element is accessed by index position. Normally the first index position of array is 0.

Types of Array

There are two types of array in Java.

1. Single Dimensional Array
2. Multi-Dimensional Array

Single Dimensional Array

Single dimensional array has only one row of data. It is also considered as simple type array. The data can be stored or accessed using simple for loop or other looping constructs.

Initialization:

  datatype[] arrayname=new datatype[size]; 

In the above example there are 8 elements in array which stores data in following manner.

Index position 0 = 23
Index position 1 = 55
Index position 2 = 34
Index position 3 = 90
Index position 4 = 37
Index position 5 = 77
Index position 6 = 16
Index position 7 = 56

Programming Example

class SingleArray
{
  public static void main(String[] args)
  {
    //Created integer type array with 5 elements
    int[] arr=new int[8];
    
    //storing data in array
    arr[0] = 23;
    arr[1] = 55;
    arr[2] = 34;
    arr[3] = 90;
    arr[4] = 37;  
    arr[5] = 77;
    arr[6] = 16;
    arr[7] = 56;
    
    //Accessing Data
    for(int i=0; i<8; i++)
    {
      System.out.println("Index Position: " + i + 
	  " Value = " + arr[i]);
    }
  }
}

Output

Multi-Dimensional Array

Multi-Dimensional array have more than one row of data. It is actually a set of single dimensional array. To access multi-dimensional array data you need to use nested loop.

Initialization

   String[][] book=new String[4][3];
   

Programming Example

class MultiArray
{
  public static void main(String[] args)
  {
    //Creating array with 2 row and 5 column
    String[][] book=new String[4][3];
    
    //Storing Data in first row
    book[0][0] = "Book";
    book[0][1] = "AuthorName";
    book[0][2] = "Age";
       
    //Storing Data in second row
    book[1][0] = "C#";
    book[1][1] = "Lyric Angel";
    book[1][2] = "30";
    
    //Storing Data in 3rd row
    book[2][0] = "Java";
    book[2][1] = "Eddy Angelil";
    book[2][2] = "34";
    
    //Storing Data in 4th row
    book[3][0] = "PHP";
    book[3][1] = "Raine Finley";
    book[3][2] = "28";
    
    
    //Accessing Data 
    
    //Traversing Row
    for(int i =0; i<4; i++)
    {
      //Traversing Column
      for(int j=0; j<3; j++)
      {
        System.out.print("book["+i+"]["+j+"] = " + 
		book[i][j]+"\t");
      }
      System.out.println("\n - - - - - - - - - -");
    }
  }
}

Output

Pass Array to a method

You can also pass an array to method. The method will process the array and return output as per your programming logic. Here, we are including a programming example in which we have created two methods that will return largest number and smallest number.

Programming Example

class ArraytoMethod
{
  public static void main(String[] args)
  {
    int[] arr=new int[5];
    arr[0] = 23;
    arr[1] = 65;
    arr[2] = 38;
    arr[3] = 10;
    arr[4] = 53;
    
    int max,min;
    max=getmax(arr);
    min=getmin(arr);
    
    System.out.println("Largest Number is " + max);
    System.out.println("Smallest Number is " + min);
  }
  
  public static int getmax(int[] a)
  {
    int num=a[0];
    for(int i=0; i<a.length; i++)
    {
      if(num < a[i])
      {
        num = a[i];
      }
    }
    return num;
  }
  public static int getmin(int[] b)
  {
    int num=b[0];
    for(int i=0; i<b.length; i++)
    {
      if(num > b[i])
      {
        num = b[i];
      }
    }
    return num;
  }
  
}

Output

Summary

In this chapter you have learned complete details of java array with programming examples. All topics are explained with suitable programming examples. In the next chapter you will learn about Strings and Collections.