Arrays in java.pptx

arrays are well developed for handling similar type of data in java.

1. ARRAYS in JAVA P NAGARAJU Asst. Professor Dept. of CSE

2. Introduction Normally , array is a collection of similar type of elements that have contiguous memory location. Java provides a data structure, the array , which 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 . Array in java is index based, first element of the array is stored at 0 index .

3. Advantage of Java Array Code Optimization: It makes the code optimized, we can retrieve or sort the data easily. Random access: We can get any data located at any index position. Disadvantage of Java Array Size Limit: We can store only fixed size of elements in the array. It doesn't grow its size at runtime. To solve this problem, collection framework is used in java . Types of Array in java There are two types of array. Single Dimensional Array Multidimensional Array

4. Single Dimensional Array in java Declaring Array Variables: Syntax dataType [] arrayRefVar ; // preferred way. Or dataType arrayRefVar []; // works but not preferred way . Creating Arrays: Syntax: arrayRefVar = new dataType [ arraySize ]; The above statement does two things: It creates an array using new dataType [ arraySize ]; It assigns the reference of the newly created array to the variable arrayRefVar .

5. Cont …. Declaring an array variable, creating an array, and assigning the reference of the array to the variable can be combined in one statement, as shown below: dataType [] arrayRefVar = new dataType [ arraySize ]; Alternatively you can create arrays as follows : dataType [] arrayRefVar = {value0, value1, ..., valuek }; Example: class  Testarray {   public static void main(String  args []){      int  a[]=new  int [5];//declaration and instantiation   a[0]=10;//initialization   a[1]=20;   a[2]=70;   a[3]=40;   a[4]=50;      // printing array   for( int   i =0;i< a.length;i ++)//length is the property of array   System.out.println (a[ i ]);      }}   

6. Example 2: class Testarray1{   public static void main(String  args []){      int  a[]={33,3,4,5};//declaration, instantiation and initialization      //printing array   for( int   i =0;i< a.length;i ++)//length is the property of array   System.out.println (a[ i ]);      }}   Output:33 3 4 5

7. public class TestArray { public static void main(String[] args ) { double [] myList = {1.9, 2.9, 3.4, 3.5}; // Print all the array elements for ( int i = 0; i < myList.length ; i ++) { System.out.println ( myList [ i ] + " "); } // Summing all elements double total = 0 ; for ( int i = 0; i < myList.length ; i ++) { total += myList [ i ]; } System.out.println ("Total is " + total); // Finding the largest element double max = myList [0]; for ( int i = 1; i < myList.length ; i ++) { if ( myList [ i ] > max) max = myList [ i ]; } System.out.println ("Max is " + max); } }

8. Passing Array to method in java We can pass the java array to method so that we can reuse the same logic on any array . Example: class Testarray2{   static void min( int   arr []){   int  min= arr [0];   for( int   i =1;i< arr.length;i ++)    if(min> arr [ i ])     min= arr [ i ];      System.out.println (min);   }      public static void main(String  args []){      int  a[]={33,3,4,5};   min(a);//passing array to method      }}  

9. Multidimensional array in java Data is stored in row and column based index (also known as matrix form ). Syntax to Declare Multidimensional Array in java dataType [][]  arrayRefVar ;  ( or)  dataType   arrayRefVar [][];  Example to instantiate Multidimensional Array in java int [][]  arr =new  int [3][3];//3 row and 3 column 

10. Example: class  Testarray3{   public static void main(String  args []){      //declaring and initializing 2D array   int   arr [][]={{1,2,3},{2,4,5},{4,4,5}};      //printing 2D array   for( int   i =0;i<3;i++){    for( int  j=0;j<3;j++){       System.out.print ( arr [ i ][j]+" ");    }     System.out.println ();   }      }}