Java Basic Programs
How to reverse a string without using a string buffer or builder?
String source="madhu";
String reverse = "";
for(int i = source.length()-1; i>=0; i--){
reverse = reverse + source.charAt(i);
}How to reverse a string keeping numbers constant?
/Two counters, l: left and r: right. Iterate from both sides and swap if alphabates
char[] inputArr = input.toCharArray();
int l = 0;
int r = inputArr.length - 1;
System.out.println(r);
while (l < r) {
if (!Character.isAlphabetic(inputArr[l])) {
l++;
} else if (!Character.isAlphabetic(inputArr[r])) {
r--;
} else {
char tempChar = inputArr[l];
inputArr[l] = inputArr[r];
inputArr[r] = tempChar;
l++;
r--;
} How to reverse a sentence by keeping all words on the same position?
String s ="This is India";
String temp="";
String[] a=s.split(" ");
int j=a.length-1;
while(j>=0)
{
temp=temp+a[j];
temp=temp+" ";
j--;
}
System.out.println(temp);
Input:This is India
Output:India is This
How To Reverse The String With Preserving The Position Of Spaces?
//Converting inputString to char array 'inputStringArray'
char[] inputStringArray = inputString.toCharArray();
//Defining a new char array 'resultArray' with same size as inputStringArray
char[] resultArray = new char[inputStringArray.length];
//First for loop :
//For every space in the 'inputStringArray',
//we insert spaces in the 'resultArray' at the corresponding positions
for (int i = 0; i < inputStringArray.length; i++) {
if (inputStringArray[i] == ' ') {
resultArray[i] = ' ';
}
}
System.out.println(resultArray);
//Initializing 'j' with length of resultArray
System.out.println("Result Array : " + resultArray[2]);
int j = resultArray.length - 1;
//Second for loop :
//we copy every non-space character of inputStringArray
//from first to last at 'j' position of resultArray
for (int i = 0; i < inputStringArray.length; i++) {
if (inputStringArray[i] != ' ') {
//If resultArray already has space at index j then decrementing 'j'
if (resultArray[j] == ' ') {
j--;
}
resultArray[j] = inputStringArray[i];
j--;
}
}
System.out.println(inputString + " ---> " + String.valueOf(resultArray));
// I am guy-- - > y ug maISaperate odd and even nos of a array such that all odd are on left side and even on right side.
/* Initialize left and right indexes */
int left = 0, right = arr.length - 1;
while (left < right)
{
/* Increment left index while we see 0 at left */
while (arr[left]%2 == 0 && left < right)
left++;
/* Decrement right index while we see 1 at right */
while (arr[right]%2 == 1 && left < right)
right--;
if (left < right)
{
/* Swap arr[left] and arr[right]*/
int temp = arr[left];
arr[left] = arr[right];
arr[right] = temp;
left++;
right--;
}
}
Array before segregation 2 3 450 92 87 90 454
Array after segregation 2 454 450 92 90 87 3write a program to print only vowels in the string.
for(int i =0; i<s1.length();i++) {
if(s1.charAt(i)=='a'|| s1.charAt(i)=='A'||
s1.charAt(i)=='e'|| s1.charAt(i)=='E'||
s1.charAt(i)=='i'|| s1.charAt(i)=='I'||
s1.charAt(i)=='o'|| s1.charAt(i)=='O'||
s1.charAt(i)=='u'|| s1.charAt(i)=='U') {
System.out.print(s1.charAt(i));
}
}write a program to print all the repeated characters in a string.
String s1 = "Madhusudan";
char[] charArray= s1.toCharArray() ;
for(int i =0; i<s1.length();i++) {
for(int j =i+1; j<charArray.length;j++) {
if(charArray[i]==charArray[j]) {
System.out.print(charArray[i]);
}
}write a program to print first non-repeated character in a string.
String s = "masdahmu";
for (int i = 0; i < s.length(); i++) {
boolean unique = true;
for (int j = 0; j < s.length(); j++) {
if (i != j && s.charAt(i) == s.charAt(j)) {
unique = false;
break;
}
}
if (unique) {
System.out.println("First non repeated characted in String \""
+ s + "\" is:" + s.charAt(i));
break;
}
}write a program to find 2nd largest number in an array.
int arr[] = {96, 1, 47, 47, 81, 92, 52, 48, 56, 66, 65, 96, 81, 6};
int largest = Integer.MIN_VALUE;
int secondLargest = Integer.MIN_VALUE;
// check the condition
for (int i = 0; i < arr.length; i++) {
// this condition check for largest number
if (arr[i] > largest) {
secondLargest = largest;
largest = arr[i];
} else if (arr[i] > secondLargest && arr[i] < largest) {
secondLargest = arr[i];
}
}
System.out.println(largest);
System.out.println(secondLargest); ///- write a program to find 2nd largest number in a array.
int a[] = {0,1,2,4,13,2,66,7,58,90,1};
//sot an array
int temp;
int len = a.length;
for (int i = 0; i < len; i++)
{
for (int j = i + 1; j < len; j++)
{
if (a[i] > a[j])
{
temp = a[i];
a[i] = a[j];
a[j] = temp;
}
}
}
for(int p =0; p<len; p++) {
System.out.println(a[p]);
}
//return 2nd last element
System.out.println(a[(len-2)]);
write a program to find 3rd largest number in a array.
// Find first
int first = arr[0];
for (int i = 1;i < arr_size ; i++)
if (arr[i] > first)
first = arr[i];
// Find second
int second = Integer.MIN_VALUE;
for (int i = 0; i < arr_size ; i++)
if (arr[i] > second &&
arr[i] < first)
second = arr[i];
// Find third
int third = Integer.MIN_VALUE;
for (int i = 0; i < arr_size ; i++)
if (arr[i] > third &&
arr[i] < second)
third = arr[i];
System.out.printf("The third Largest " + element is %d", third);
Write a program to remove all vowels in a string.
//Metod 1
String s1="madhu";
String Result ="";
for(int i=0;i<s1.length();i++) {
if(!Isvowel(Character.toLowerCase(s1.charAt(i)))){
Result=Result+s1.charAt(i);
}
}
System.out.println(Result);
public static boolean Isvowel(char c) {
String vowels = "aeiou";
for(int i=0; i<5 span="">i++)
{
if(c == vowels.charAt(i))
{
return true;
}
}
return false;
}
//Method 2
String str = "RemoveVowels";
String resustr = str.replaceAll("[aeiouAEIOU]", "");
System.out.println(resustr);
how to remove a particular character in a string.
//method1
String str = "India is my country";
System.out.println(charRemoveAt(str, 7));
public static String charRemoveAt(String str, int p) {
return str.substring(0, p) + str.substring(p + 1);
}
//method2
String s1="madhu";
s1 = s1.replace("d", "");
System.out.println(s1);write a program to read data from excel.
String FilePath = "d://filepath.xls";
FileInputStream fs = new FileInputStream(FilePath);
Workbook wb = Workbook.getWorkbook(fs);
Workbook wb = Workbook.getWorkbook(new File("samplefile.xls"));
Sheet sh = wb.getSheet(0); // this is to get the access to Sheet1.
Sheet sh = wb.getSheet(1);
Sheet sh = wb.getSheet("sheet1");
int totalNoOfRows = sh.getRows();
int totalNoOfCols = sh.getColumns();
for (int row = 0; row < totalNoOfRows; row++) {
for (int col = 0; col < totalNoOfCols; col++) {
System.out.print(sh.getCell(col, row).getContents() + "\t");
}
System.out.println();
}
//Additional -
String CellGetContent = sh.getCell(0, 0).getContents();
System.out.println(CellGetContent);
//OR
Cell Row0Col0 = sheet.getCell(0, 0);
Cell Row1Col1 = sheet.getCell(1, 1);
String FirstRowFirstColumn = Row0Col0.getContents();
String SecondRowSecondColumn = Row1Col1.getcontents();use of iterator?
The iterator is used for iterating (looping) various collection classes such as HashMap, ArrayList, LinkedList, etc.
List names = new LinkedList < > ();
names.add("Rams");
names.add("Posa");
names.add("Chinni");
// Getting Iterator
Iterator namesIterator = names.iterator();
// Traversing elements
while (namesIterator.hasNext()) {
System.out.println(namesIterator.next());
}Swap two numbers without using third variable.
int x = 10, y = 5;
// Code to swap 'x' and 'y'
x = x + y; // x now becomes 15
y = x - y; // y becomes 10
x = x - y; // x becomes 5Java code to display all odd/even numbers between given range:
public static int[] returnOdd(int l,int r) {
int m =0;
int size = ((r-l)/2)+1;
int[] arr = new int[size] ;
for(int i=l;i<=r;i++) {
if(i%2!=0) {
arr[m]=i;
m++;
}
}
return arr;
}
Java code to reverse a number:
public static int reverseNumber(int number) {
int reverse = 0;
while(number!=0) {
reverse = (reverse*10)+(number%10);
number = number/10;
}
return reverse;
}Java code to search a number in an aray:
public static String searchNumber(int arr[],int num) {
int flag = 0;
for(int i=0;i<=arr.length-1;i++) {
if(arr[i]==num) {
flag = 1;
break;
}else flag = 0;
}
if(flag==1)
return "YES";
else return "NO";
}
Write a program to check for the occurrence of each character of a string.
String input = "maadhu";
HashMap<Character, Integer> hash = new HashMap<Character, Integer>();
for(int i =0; i<input.length()-1;i++){
if(hash.containsKey(input.charAt(i)))
hash.put(input.charAt(i), hash.get(input.charAt(i))+1);
else
hash.put(input.charAt(i), 1);
}
//Print
for(Map.Entry m : hash.entrySet() ){
System.out.println(m.getKey());
System.out.println(m.getValue());
}Write a selenium script to click on all links and check for the status of the page whether it is throwing an error or not
List<WebElement> links = driver.findElements(By.tagName("a"));
List<String> brokenLinks;
Iterator itr = links.iterator();
int respCode=200;
HttpURLConnection huc=null;
while(itr.hasNext()){
WebElement l = itr.next();
try{
url = it.next().getAttribute("href");
huc = (HttpURLConnection)(new URL(url).openConnection());
huc.setRequestMethod("HEAD");
huc.connect();
respCode = huc.getResponseCode();
if(respCode >= 400){
brokenLinks.add(url)
System.out.println(url+" is a broken link");
}catch(Exception E){
e.printStackTrace();
}
}
}
Write a function that takes integer array A as an input parameter and returns the integer(s smallest +ve no > 0 and not present in A) from this function
A= [1,3,6,4,1,2 ]=> 5
A = [1,2,3] -> 4
A =[-1,-3]-> 1
Ans:
int[] A ={1,3,6,4,1,2};
int N = A.length;
Set<Integer> set = new HashSet<>();
for (int a : A) {
if (a > 0) {
set.add(a);
}
}
for (int i = 1; i <= N + 1; i++) {
if (!set.contains(i)) {
System.out.println(i);
break;
}
}