Java Programming

Java Programming

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  Ms. K.Nanthini Assistant Professor, Konguengineering college, Erode, Tamilnadu JAVA ARRAYS AND OPERATORS
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  Java Arrays -Java arrayis an object which contains elements of a similar data type or container that holds data (values) of one single type -elements of an array are stored in a contiguous memory location - first element of the array is stored at the 0th index, 2nd element is stored on 1st index and so on. -length of the array using the length member. In C/C++, we need to use the sizeof operator -Like C/C++, we can also create single dimentional or multidimentional arrays in Java -Java provides the feature of anonymous arrays which is not available in C/C++
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  (cont.,) Advantages Code Optimization: Itmakes the code optimized, we can retrieve or sort the data efficiently. Random access: We can get any data located at an index position. Disadvantages Size Limit: We can store only the 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 which grows automatically.
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  (cont.,) Syntax to declarean array-Single dimension dataType[] arr; (or) dataType []arr; (or) dataType arr[]; Instantiation of an Array in Java arrayRefVar=new datatype[size]; -creating an object-creating instance of the class
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  Example //Java Program toillustrate how to declare, instantiate, initialize //and traverse the Java array. 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]=30; a[3]=40; a[4]=50; //traversing array for(int i=0;i<a.length;i++)//length is the property of array System.out.println(a[i]); }}
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  (Cont.,) int a[]={33,3,4,5};//declaration, instantiationand initialization 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]); }}
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  for each loop TheJava for-each loop prints the array elements one by one. It holds an array element in a variable, then executes the body of the loop. for(data_type variable:array){ //body of the loop } //Java Program to print the array elements using for-each loop class Testarray1{ public static void main(String args[]){ int arr[]={33,3,4,5}; //printing array using for-each loop for(int i:arr) System.out.println(i); }}
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  Passing Array toa Method class Testarray2{ //creating a method which receives an array as a parameter 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};//declaring and initializing an array min(a);//passing array to method } } Guess the output?
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  Anonymous Array inJava public class TestAnonymousArray{ //creating a method which receives an array as a parameter static void printArray(int arr[]) { for(int i=0;i<arr.length;i++) System.out.println(arr[i]); } public static void main(String args[]){ printArray(new int[]{10,22,44,66});//passing anonymous array to method }}
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  Returning Array fromthe Method //Java Program to return an array from the method class TestReturnArray{ //creating method which returns an array static int[] get(){ return new int[]{10,30,50,90,60}; } public static void main(String args[]){ //calling method which returns an array int arr[]=get(); //printing the values of an array for(int i=0;i<arr.length;i++) System.out.println(arr[i]); }}
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  ArrayIndexOutOfBoundsException Java Virtual Machine(JVM) throws an ArrayIndexOutOfBoundsException if length of the array in negative, equal to the array size or greater than the array size while traversing the array. //Java Program to demonstrate the case of //ArrayIndexOutOfBoundsException in a Java Array. public class TestArrayException{ public static void main(String args[]){ int arr[]={50,60,70,80}; for(int i=0;i<=arr.length;i++){ System.out.println(arr[i]); } }}
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  Output Exception in thread"main" java.lang.ArrayIndexOutOfBoundsException: 4 at TestArrayException.main(TestArrayException.java:7) 50 60 70 80
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  Multidimensional Array Syntax toDeclare dataType [][]arrayRefVar; (or) dataType arrayRefVar[][]; (or) dataType []arrayRefVar[]; Example to instantiate int[][] arr=new int[3][3];//3 row and 3 column Example to initialize arr[0][0]=1; arr[0][1]=2; arr[0][2]=3; arr[1][0]=4; arr[1][1]=5; arr[1][2]=6; arr[2][0]=7; arr[2][1]=8; arr[2][2]=9;
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  Example //Java Program toillustrate the use of multidimensional array 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(); } }}
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  Jagged Array creating oddnumber of columns in a 2D array, it is known as a jagged array. In other words, it is an array of arrays with different number of columns. class TestJaggedArray{ public static void main(String[] args){ //declaring a 2D array with odd columns int arr[][] = new int[3][]; arr[0] = new int[3]; arr[1] = new int[4]; arr[2] = new int[2]; //initializing a jagged array int count = 0; for (int i=0; i<arr.length; i++) for(int j=0; j<arr[i].length; j++) arr[i][j] = count++; //printing the data of a jagged array for (int i=0; i<arr.length; i++){ for (int j=0; j<arr[i].length; j++){ System.out.print(arr[i][j]+" "); } System.out.println();//new line}}}
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  Practice Questions 1) JavaProgram to copy all elements of one array into another array 2) Java Program to find the frequency of each element in the array 3) Java Program to left rotate the elements of an array 4) Java Program to print the duplicate elements of an array 5) Java Program to print the elements of an array 6) Java Program to print the elements of an array in reverse order 7) Java Program to print the elements of an array present on even position 8) Java Program to print the elements of an array present on odd position
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  (Cont.,) 9) Java Programto print the largest element in an array 10) Java Program to print the smallest element in an array 11) Java Program to print the number of elements present in an array 12) Java Program to print the sum of all the items of the array 13) Java Program to right rotate the elements of an array 14) Java Program to sort the elements of an array in ascending order 15) Java Program to sort the elements of an array in descending order 16) Find 3rd Largest Number in an Array 17) Find 2nd Largest Number in an Array 18) Find Largest Number in an Array 19) Find 2nd Smallest Number in an Array
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  (Cont.,) 20) Find SmallestNumber in an Array 21) Remove Duplicate Element in an Array 22) Add Two Matrices 23) Multiply Two Matrices 24) Print Odd and Even Number from an Array 25) Transpose matrix 26) Java Program to subtract the two matrices 27) Java Program to determine whether a given matrix is an identity matrix 28) Java Program to determine whether a given matrix is a sparse matrix
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  (Cont.,) 29) Java Programto determine whether two matrices are equal 30) Java Program to display the lower triangular matrix 31) Java Program to display the upper triangular matrix 32) Java Program to find the frequency of odd & even numbers in the given matrix 33) Java Program to find the product of two matrices 34) Java Program to find the sum of each row and each column of a matrix 35) Java Program to find the transpose of a given matrix