java arrays
TRANSCRIPT
JavaArraysFunctions
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ArraysStep1 : Create a reference. Cannot
mention the size.◦ Datatype [ ] arrname; ◦ Datatype arrname[ ]; Valid – not
recommended Step 2 : Reserve memory
◦ arrname = new datatype[SIZE];Step3 : Access elementsArray index begins from 0.int [] a = {5 , 8 , 10}; //Valid (decl + def).
Arraysint [] a , b; int c [ ] , d;a and b; both are arraysc is array and d is not a array
ArraysTo know the number of elementsArr.length int [ ] arr1 = {3 , 9 , 1, 4 , 7 };System.out.println(arr1.length);int [ ] arr2;System.out.println(arr2.length);int [ ] arr3;arr3 = new int[10];System.out.println(arr3.length);
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Array - Accessing elements Method 1 :Find Length : arr.length for(int index = 0; index < arr.length ;
index++) System.out.println(arr[index]);Method 2:for(int x : arr) System.out.println(x);
int [ ] arr = {3 , 9 , 1, 4 , 7 };for(int val : arr)
System.out.println(val);float [ ] arr = {3 , 9 , 1, 4 , 7 };for(float val : arr)
System.out.println(val);int [ ] arr = {3 , 9 , 1, 4 , 7 }; int val;for(val : arr)
System.out.println(val);
Can we use == to compare arrays?int [] arr1 = {7 , 5 , 2 , 8};int [] arr2 = {7 , 5 , 2 , 8}; if(arr1 == arr2)
System.out.println("Equal");else
System.out.println("Not Equal");
1. int [] arr1 = {7 , 5 , 2 , 8};2. int [] arr2 ;3. arr2 = arr1;4. if(arr1 == arr2)5.
System.out.println("Equal");6. else7. System.out.println("Not
Equal");
Can we use == to compare arrays?
Can we assign character variable to integer?1. char c = 'A';2. int x = c; Can we assign from character array to integer array? 3. char [] carr = {'S','I','K'};4. int [] iarr = carr;
int [] arr;arr = new int[5];arr[0] = 12;arr[1] = 23;arr[2] = 34;
for(int i = 0 ; i < arr.length ; i++) System.out.println(arr[i]);
Multi-dimensional Arrayint [] [] marks; int row = 3;int col = 4; marks = new int[row][col]; for(int i = 0 ; i < row ; i++) for(int j = 0 ; j < col ; j+
+) marks[i][j] = i + j;
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Multi-dimensional ArraysMethod1 : Declare and initialise int [][] a = { {1 , 2 , 3 , 4} , {5,6,7} , {8}};1st row has 4 col, 3rd row has 1 col. System.out.println("No. of Rows = " + a.length); for(int x = 0 ; x < a.length ; x++) System.out.println("No. of Columns in " + x + " =
" + a[x].length);
for(int r = 0 ; r < a.length ; r++) { for(int c = 0 ; c < a[r].length ; c++) System.out.print(a[r][c] + " "); }
int [] [] marks; int row = 3;int col = 4;
marks = new int[row][];
for(int i = 0 ; i < row ; i++)for(int j = 0 ; j < col ; j++)marks[i][j] = i + j;
for(int i = 0 ; i < row ; i++)marks[i] = new int[col];
Multi-dimensional Array
Multi-Dimensional Arrayint [][] mat = {{5 , 8 , 9 } , {2 , 4
} , {6}};mat[0][0] mat[0][1] mat[0][2] mat[1][0] mat[1][1] mat[1][2] mat[2][0] mat[2][1] mat[2][2]
mat[0][0] mat[0][1] mat[0][2] mat[1][0] mat[1][1] mat[1][2] mat[2][0] mat[2][1] mat[2][2]
Copying Arraysint [] arr1 = {5 ,8 , 10, 15, 20};int [] arr2; arr2 = arr1;
for(int x: arr2)System.out.println(x);
arr1[0] = 2; arr1[1] = 4; for(int x: arr2)
System.out.println(x);
System.arraycopy(src Array, src pos, destination Array, dest pos, length);
int [] arr1 = {5 ,8 , 10, 15, 20};int [] arr2 = new int[5]; System.arraycopy(arr1, 0, arr2,
0, 5);
int [] arr1 = {5 ,8 , 10, 15, 20}; int [] arr2 = Arrays.copyOf(arr1, 5);for(int x: arr2) System.out.println(x);
Sorting of Array Arrays.sort(Type [] arr); Arrays.sort(Type [], int fromIndex, int toIndex);
int arr[] = {5,2,9,1,2,8}; Arrays.sort(arr); OR Arrays.sort(arr,0,6); Output : 1 2 2 5 8 9
int arr[] = {5,2,9,1,2,8}; Arrays.sort(arr,1,5); Output : 5 1 2 2 9 8
Anonymous Arrays
public static void printArray(int [] x) { for(int i : x) System.out.println(x); } public static void main(String [] args) { int [] marks = {3,6,4,7}; 1. printArray(marks); 2. printArray(1 ,3 ,5 ,7); 3. printArray([]{1 ,3 ,4 ,5}); 4. printArray(new int []{1 ,3 ,4 ,5}); }
Identify the valid calls to printArray?
FUNCTIONS
Argument Passing public static void function(int x) { x = 20; System.out.println("Function " + x); } public static void main(String [] args) { int x = 5; function(x); System.out.println("Main " + x); }
Passing Array to Functionpublic class ArgumentPassingArray { public static void function(int [] arr) { arr[0] = 20;
} public static void main(String [] args) { int [] arr = {5,8,10}; function(arr); System.out.println("Main " + arr[0]); }}
String str;str = new String("SIKANDER");System.out.println(str.hashCode());str = str.toLowerCase();System.out.println(str.hashCode());
Argument Passing to Functionclass Rectangle { int length ; int breadth; Rectangle(int l , int b) { length = l ; breadth = b; }}public class FunctionDemo { public static void function(Rectangle x) { x.length = 20; System.out.println("Function " + x.length + " " + x.breadth); } public static void main(String [] args) { Rectangle obj = new Rectangle(4 ,5 ); function(obj); System.out.println("Main " + obj.length + " " + obj.breadth); }}
class Rectangle { int length ; int breadth; Rectangle(int l , int b) { length = l ; breadth = b; }}public class FunctionDemo { public static void function(Rectangle x) {
x = new Rectangle( 7 , 9);System.out.println("Function " + x.length + " " + x.breadth);
} public static void main(String [] args) { Rectangle obj = new Rectangle(4 ,5 ); function(obj); System.out.println("Main " + obj.length + " " + obj.breadth); }}