Programming

2. Real Time Problem
Ramesh is a Teacher. He needs to store marks
of 12 students in his class.
HOW?

3. Solution 1
Ramesh can create twelve set of
variables to store marks of twelve
students.
S1 S2 S12
S3 … … ...
Mark1 Mark3 Mark12
Mark2

4. Solution 2
He can create one variable called mark in
that mark he can store marks of twelve
Students
S1 S2 S3 S3 S12
Mark

5. Array
Java array is an object which contains elements of a similar data type.

6. • 1D array
• 2D array
Array Types

7. How to declare an array
dataType[] arrayName;
Example:
int[] data;
data = new int[10];
(or)
int[] data=new int[10];

8. • Static 1D array
• Dynamic 1D array
Memory Allocation

9. Java array index
int data[]=new int[5];
Last element
First element
data[0] data[1] data[2] data[3] data[4]
Index Array data of length 5
1 2 3 4 5
0 1 2 3 4

10. • boolean : false
• int : 0
• double : 0.0
• String : null
• User Defined Type : null
Default array values

11. public class ArrayDemo
{
public static void main(String[] args){
String str[] = new String[5];
for (String s : str)
System.out.print(s + " ");
System.out.println();
int num[] = new int[5];
for (int val : num)
System.out.print(val + " ");
System.out.println();
double dnum[] = new double[5];
for (double val : dnum)
System.out.print(val + " ");
System.out.println();
boolean bnum[] = new boolean[5];
for (boolean val : bnum)
System.out.print(val + " ");
}
}
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12. null null null null null
0 0 0 0 0
0.0 0.0 0.0 0.0 0.0
false false false false false
OUTPUT

13. //Memory Allocation
int marks[] = new int[4];
marks[0] = 1
marks[1] = 2
marks[2] = 3
marks[3] = 4
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1000
1001
1005
1006
1002
1003
1004
1007
1008
1009
...
2000
0
0
0
0
marks[0]
marks[1]
marks[2]
marks[3]
1
2
3
4

14. Storage of Arrays
Stack area
int marks[]= new int[]4
Heap Memory
1 2 3 4

15. How to access elements from an array?
First element - marks[0]
Second element – marks[1]
Third element – marks[2]
Fourth element – marks[3]
Fifth element – marks[4]
marks[ ] = { };
size = 5
5 15, 24, 45, 34, 60
To access any nth element,
marks[n-1]
0, 1, 2, 3, 4 - index

16. // Predict the output
import java.util.*;
public class Main
{
public static void main(String[] args)
{
int[] arr = {12, 4, 5, 2, 5};
for (int i = 0; i < arr.length; i++)
{
System.out.print(arr[i] + " ");
}
}
}
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17. // Predict the output
import java.util.*;
public class Main
{
public static void main(String[] args)
{
Scanner s=new Scanner(System.in);
int n = s.nextInt();
int arr[]=new int[n];
for(int i = 0; i < arr.length; i++)
{
arr[i] = s.nextInt();
}
for (int i = 0; i < arr.length; i++)
{
System.out.print(arr[i] + " " );
}
}
}
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18. //Java Array of Objects
class Std {
String name;
public Std(String name){
this.name = name;
}
}
public class Main {
public static void main(String args[]) throws Exception {
Std myArray[] = new Std[3];
myArray [0] = new Std("Java");
myArray [1] = new Std("Object");
myArray [2] = new Std("Array");
for(Std str:myArray)
{
System.out.println(str.name);
}
}
}
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19. Storage of Arrays
Stack area
myArray[]
Heap Memory
obj1 obj2 obj3
new Std(“Java”)
new
Std(“Object”)
new Std(“Array”)

20. Anonymous Array
• An array in Java without any name is called anonymous array.
• It is just for instant use (i.e. one time usage) .
• Anonymous array is passed as an argument of method.
Syntax:
new Datatype[] {val1, val2..valn};

21. import java.util.*;
public class MyClass {
public static void main(String args[])
{
int s1 = sum(new int[]{1,2,3,4,5});
System.out.print(s1);
}
public static int sum(int a[])
{
int total = 0;
for(int i:a)
{
total = total+i;
}
return total;
}
}
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22. THANK YOU