# Java Coding Interview Questions
## 1. String ko reverse karo
```java
String reverse(String s) {
return new StringBuilder(s).reverse().toString();
}
```
## 2. Palindrome check karo
```java
boolean isPalindrome(String s) {
String rev = new StringBuilder(s).reverse().toString();
return s.equals(rev);
}
```
## 3. Fibonacci series (n terms)
```java
void fibonacci(int n) {
int a = 0, b = 1;
for (int i = 0; i < n; i++) {
System.out.print(a + " ");
int temp = a + b;
a = b;
b = temp;
}
}
```
## 4. Array mein duplicate find karo
```java
void findDuplicates(int[] arr) {
Set<Integer> seen = new HashSet<>();
for (int num : arr) {
if (!seen.add(num)) {
System.out.println("Duplicate: " + num);
}
}
}
```
## 5. Two Sum problem
```java
int[] twoSum(int[] nums, int target) {
Map<Integer, Integer> map = new HashMap<>();
for (int i = 0; i < nums.length; i++) {
int complement = target - nums[i];
if (map.containsKey(complement))
return new int[]{map.get(complement), i};
map.put(nums[i], i);
}
return new int[]{};
}
```
## 6. String mein vowels count karo
```java
int countVowels(String s) {
int count = 0;
for (char c : s.toLowerCase().toCharArray())
if ("aeiou".indexOf(c) != -1) count++;
return count;
}
```
## 7. Factorial (recursive)
```java
long factorial(int n) {
if (n <= 1) return 1;
return n * factorial(n - 1);
}
```
## 8. Array ko sort karo (bubble sort)
```java
void bubbleSort(int[] arr) {
int n = arr.length;
for (int i = 0; i < n - 1; i++)
for (int j = 0; j < n - i - 1; j++)
if (arr[j] > arr[j + 1]) {
int temp = arr[j];
arr[j] = arr[j + 1];
arr[j + 1] = temp;
}
}
```
## 9. Second largest element dhundho
```java
int secondLargest(int[] arr) {
int first = Integer.MIN_VALUE, second = Integer.MIN_VALUE;
for (int n : arr) {
if (n > first) { second = first; first = n; }
else if (n > second && n != first) second = n;
}
return second;
}
```
## 10. Anagram check karo
```java
boolean isAnagram(String s1, String s2) {
char[] a = s1.toCharArray();
char[] b = s2.toCharArray();
Arrays.sort(a);
Arrays.sort(b);
return Arrays.equals(a, b);
}
```Back to Course