typical programming questions asked for 7+ years Java experience

1. Reverse a String

String s = "Java";
String rev = "";
for(int i=s.length()-1;i>=0;i--){
  rev = rev + s.charAt(i);
}
System.out.println(rev);

---

2. Check Palindrome

String s = "madam";
String rev = "";
for(int i=s.length()-1;i>=0;i--){
  rev += s.charAt(i);
}
System.out.println(s.equals(rev));

---

3. Find Duplicate Characters in String

String s = "programming";
Map map = new HashMap<>();
for(char c : s.toCharArray()){
  map.put(c, map.getOrDefault(c,0)+1);
}
for(char c : map.keySet()){
  if(map.get(c) > 1)
    System.out.println(c);
}

---

4. Find Second Largest Number in Array

int arr[] = {10,20,50,40};
int largest = Integer.MIN_VALUE;
int second = Integer.MIN_VALUE;

for(int n : arr){
  if(n > largest){
    second = largest;
    largest = n;
  }else if(n > second && n != largest){
    second = n;
  }
}
System.out.println(second);

---

5. Sort HashMap by Value

Map map = new HashMap<>();
map.put("A",30);
map.put("B",10);
map.put("C",20);

map.entrySet().stream()
   .sorted(Map.Entry.comparingByValue())
   .forEach(System.out::println);

---

6. Remove Duplicates from List

List list = Arrays.asList(1,2,2,3,4,4);
Set set = new LinkedHashSet<>(list);
System.out.println(set);

---

7. Count Words in String

String s = "Java is easy language";
String[] words = s.split(" ");
System.out.println(words.length);

---

8. Find First Non-Repeated Character

String s = "swiss";
Map map = new LinkedHashMap<>();
for(char c : s.toCharArray()){
  map.put(c, map.getOrDefault(c,0)+1);
}
for(char c : map.keySet()){
  if(map.get(c) == 1){
    System.out.println(c);
    break;
  }
}

---

9. Reverse LinkedList

Collections.reverse(list);

---

10. Find Missing Number in Array

int arr[] = {1,2,4,5};
int n = 5;
int sum = n*(n+1)/2;
int actual = 0;
for(int i : arr) actual += i;
System.out.println(sum - actual);

---

11. Check Prime Number

int n = 7;
boolean prime = true;
for(int i=2;i<=n/2;i++){
 if(n%i==0){ prime=false; break; }
}
System.out.println(prime);

---

12. String Anagram

char[] a = "listen".toCharArray();
char[] b = "silent".toCharArray();
Arrays.sort(a);
Arrays.sort(b);
System.out.println(Arrays.equals(a,b));

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13. Find Frequency of Elements

int arr[] = {1,2,2,3};
Map map = new HashMap<>();
for(int i:arr){
 map.put(i,map.getOrDefault(i,0)+1);
}
System.out.println(map);

---

14. Find Max Occurring Character

String s = "banana";
Map map = new HashMap<>();
for(char c:s.toCharArray()){
 map.put(c,map.getOrDefault(c,0)+1);
}
System.out.println(Collections.max(map.entrySet(),
 Map.Entry.comparingByValue()).getKey());

---

15. Thread using Runnable

class MyThread implements Runnable{
 public void run(){
  System.out.println("Thread running");
 }
}
new Thread(new MyThread()).start();

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Source: sureshtechlabs.com

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