Core Java with OCJP/SCJP: Language Fundamentals Part-6 || Arrays Part-1

[comedyhits]

Arrays

1) introduction
2) Array Declaration
3) Array Creation
4) Array Initialization
5) Array declaration, Creation & initialization in a single line
6) lenght vs lenght()
7) Anonymous Array
8) array elements assignment
9) Array Variable assignment

Introduction

an array is an indexed collection of a fixed number of homogeneous data elements
the main advantage of arrays is we can represent a huge number of values by using a single variable so that the readability of the code will be improved but the main disadvantage of arrays are
fixed in size that is once we create an array there is no chance of increasing or decreasing the size based on our requirement hence to use the arrays concept compulsory we should
know the size in advance, which may not possible always.

Array Declaration

one-dimensional array declaration

int[] x; valid best practice recommended because the name is clearly separated from the type
int []x; valid
int x[]; valid

at the time of declaration, we can't specify the size otherwise we will get a compile-time error
int[6] x; invalid
int[] x; valid

two-dimensional array declaration

int[][] x; valid
int [][]x; valid
int x[][]; valid
int[] []x; valid
int[] x[]; valid
int []x[]; valid

which of the following is valid

int[] a, b; valid a= 1 b= 1 dimensional
int[] a[], b; valid a=2 b=1 dimensional
int[] a[], b[]; valid a=2 b=2 dimensional
int[] []a, b; valid a=2, b=2 dimensional
int[] []a, b[]; valid a=2, b=3 dimensional
int[] []a, []b; invalid if we want to specify dimensional before the variable that facility is applicable only for 1st variable in a declaration

if we are trying to apply for the remaining variables we will get a compile-time error

int[] []a, []b, []c; a is valid b is invalid c is invalid

3-dimensional array declaration

int[][][] a;
int [][][]a;
int a[][][];
int[] [][]a;
int[] a[][];
int[] []a[];
int[][] []a;
int[][] a[];
int [][]a[];
int []a[][]; these all are valid

Array creation

every array in java is an object only hence we can create arrays by using a new operator

int[] a=new int[3];

for every array type corresponding classes are available and these classes are part of the java language and not available to the program level

example

class Test{
public static void main(String[] args){
int[] x= new int[3];
//[I
}
}


array, corresponding class name

int[] [I
int[][] [[I
double[] [D
short[] [S
byte[] [B
boolean[] [Z

loopholes for creating arrays

1) at the time of array creation compulsory we should specify the size otherwise we will get compile time error

int[] x=new int[]; invalid
int[] x=new int[6]; valid


2) it is legal to have an array with size zero in java

int[] x=new int[0]; valid

3) if we are trying to specify array size with some -ve int value then we will get a run time exception saying negative array size exception

int[] x=new int[-3]; valid RE: negative arror size exception

4) to specify array size the allowed data types are byte, short, char, and int if we are trying to specify any other type then we will get CE:

int[] x=new int[10]; valid
int[] x=new int['a']; valid

byte b=20;
int[] x=new int[b]; valid

short s=30;
int[] x=new int[s]; valid

int[] x=new int[10l]; incalid CE; p l p found long required int

the maximum allowed array size in java is 2147483647 which is the maximum value of the int data type

int[] x=new int [2147483647]; valid RE: even in the case we may get a run time exception if sufficient heap memory is not available
int[] x=new int[2147483648]; invalid CE ; integer number is too large

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[Abhi-rknp]

0:14 - Eras
0:19 - Agenda: Introduction, Array Declaration, Array Creation, Array Initialization
1:05 - Declaration, Creation, and Initialization in a Single Line
1:38 - Length vs length (Java length variable vs length method)
1:51 - Anonymous Arrays
2:05 - Array Element Assignments
2:19 - Array Variable Assignments
2:37 - Introduction to Arrays: Need, Purpose, Advantages, Disadvantages
3:05 - Example: int x = 10
4:17 - Representing 10, 000 Values with an Array
5:04 - Advantages of Arrays
5:51 - Limitations of Arrays: Fixed Size
6:09 - Example: Classroom Scenario (Fixed Size Limitation)
7:12 - Array Limitations: Homogeneous Data Types Only
8:02 - Collections as a Solution to Array Limitations
8:30 - Definition of an Array
9:08 - Main Advantage of Arrays
10:05 - Readability Improvement with Arrays
10:49 - Main Disadvantage: Fixed Size
12:16 - Summary and Conclusion

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