How do you sort the keys in HashMap?

Problem statement:
Write the java code to sort the keys in HashMap.

1. import java.util.HashMap;
2. import java.util.Set;
3. import java.util.TreeSet;
4. public class Test {
5. public static void main(String[] args) {
6. HashMap<String, String> m = new HashMap<String, String>();
7. m.put("key45", "aa");
8. m.put("key12", "zz");
9. m.put("key39", "cc");
10. m.put("key27", "bb");
11. Set<String> s = m.keySet();
12. s = new TreeSet<String>(s);
13. System.out.println(s);
14. }
15. }

Output:
[key12, key27, key39, key45]

How do you sort the values in HashMap?

Problem statement:
Write the java code to sort the values in HashMap.

1. import java.util.Collection;
2. import java.util.HashMap;
3. import java.util.TreeSet;
4. public class Test {
5. public static void main(String[] args) {
6. HashMap<String, String> m = new HashMap<String, String>();
7. m.put("key45", "aa");
8. m.put("key12", "zz");
9. m.put("key39", "cc");
10. m.put("key27", "bb");
11. Collection<String> c = m.values();
12. c = new TreeSet<String>(c);
13. System.out.println(c);
14. }
15. }

Output:

[aa, bb, cc, zz]

Which of the following option will sort the keys in HashMap ?

Problem statement:

Given java code as follows, can you find out the correct option to sort the keys in HashMap?

1. import java.util.HashMap;
2. import java.util.Set;
3. import java.util.TreeSet;
4. public class Test {
5. public static void main(String[] args) {
6. HashMap<String, String> m = new HashMap<String, String>();
7. m.put("key45", "aa");
8. m.put("key12", "bb");
9. m.put("key39", "cc");
10. Set<String> s = m.keySet();
11.   // code goes here
12. s = new TreeSet(s);
13.  }
14. }

• Arrays.sort(s);
• s = new TreeSet(s);
• Collections.sort(s);
• s = new SortedSet(s);

Correct option: 

s = new TreeSet(s);
Explanation:
Arrays.sort(s) // sorts for static array 
Collection.sort(s) // sort the List type of object not Set type
s =new SortedSet(s); // SortedSet is an interface

Write an algorithm to find N’th smallest element in an Unsorted Array.

Problem statement:
Given an array of positive and negative unsorted integer. Can you write an algorithm to find out the nth smallest element in the array.

1. public class NthSmallestElement {
2. public static void main(String[] args) {
3. int a[] = { 3, 4, 1, 105, 10, -10 };
4.   int thirdSmallest = 3;
5. int min= nthSmallestElement(a, thirdSmallest );
6. System.out.println(min);
7. }
8. public static int nthSmallestElement(int a[], int n) {
9. // Sort the given array
10. Arrays.sort(a);
11. // Return n'th element in the sorted array
12. return a[n - 1];
13. }
14. }

Output:

3

Write an algorithm to find N’th largest element in an Unsorted Array.

Problem statement:
Given an array of positive and negative unsorted integer. Can you write an algorithm to find out the nth largest element in the array.

1. public class NthLargestElement {
2. public static void main(String[] args) {
3. int a[] = { 3, 4, 1, 105, 10, -10 };
4.                 int thirdLargest = 3;
5. int max = nthLargestElement(a, thirdLargest);
6. System.out.println(max);
7. }
8. public static int nthLargestElement(int a[], int n) {
9. // Sort the given array
10. Arrays.sort(a);
11. // Return n'th element in the sorted array
12. return a[a.length - n];
13. }
14. }

Output:

4

Write an algorithm to find out the second smallest element in an array.

Problem statement:
Given an array of positive and negative unsorted integer. Can you write an algorithm to find out the second smallest element in the array.

1. public class SecondMinElement {
2. public static void main(String[] args) {
3. int a[] = { 3, 4, 1, 105, 10, -10 };
4. int firstMin = Integer.MAX_VALUE;
5. int secondMin = Integer.MAX_VALUE;
6. for (int i = 0; i < a.length; i++) {
7. if (a[i] < firstMin) {
8. secondMin = firstMin;
9. firstMin = a[i];
10. } else if (a[i] < secondMin) {
11. secondMin = a[i];
12. }
13. }
14. System.out.println("Second min element: " + secondMin);
15. }
16. }

Output:

Second min element: 1

Write an algorithm to find out the second largest element in an array.

Problem statement:
Given an array of positive and negative unsorted integer. Can you write an algorithm to find out the second largest element in the array.

1. public class SecondMaxElement {
2. public static void main(String[] args) {
3. int a[] = { 3, 4, 1, 105, 10, -10 };
4. int firstMax = Integer.MIN_VALUE, // large -ve value
5.   int secondMax = Integer.MIN_VALUE; // large -ve value
6. for (int i = 0; i < a.length; i++) {
7. if (a[i] > firstMax) {
8. secondMax = firstMax;
9. firstMax = a[i]; // a[0] becomes first max
10. } else if (a[i] > secondMax) {
11. secondMax = a[i];
12. }
13. }
14. System.out.println(secondMax);
15. }
16. }

Output:

10

What is the output of the given java code?

Problem statement:
Given java code, what will be the output of it?

1. interface Car {
2. public void startEngine();
3. }
4. class MySuzuki implements Car {
5. public void startEngine() {
6. System.out.println("MySuzuki");
7. }
8. }
9. class MyFerrari implements Car {
10. public void startEngine() {
11. System.out.println("MyFerrari");
12. }
13. }
14. public class OOPSExample {
15. public static void main(String[] args) {
16. MyFerrari obj = new MySuzuki();
17. obj.startEngine();
18. }
19. }

Output:

Compile time error at line 16, due to Type mismatch: cannot convert from MySuzuki to MyFerrari

What is the output of the code?

Problem statement:
Given java code, what will be the output of it?

1. interface Car {
2. public void startEngine();
3. }
4. class MySuzuki implements Car {
5. public void startEngine() {
6. System.out.println("MySuzuki");
7. }
8. }
9. class MyFerrari implements Car {
10. public void startEngine() {
11. System.out.println("MyFerrari");
12. }
13. }
14. public class OOPSExample {
15. public static void main(String[] args) {
16. Car obj = new MySuzuki();
17. obj.startEngine();
18. }
19. }

Output:

MySuzuki

Can you write an algorithm to check palindrome?

Problem statement:
Given a string. Can you check whether it is a palindrome or not?

1. public class Palindrome {
2. public static void main(String[] args) {
3. String s = "abcba";
4. char c[] = s.toCharArray();
5. int p = c.length - 1;
6. for (int i = 0; i < c.length / 2; i++) {
7. if (c[i] == c[p]) {
8. p--;
9. } else {
10. System.out.println("Not palindrome");
11. return;
12. }
13. }
14. System.out.println("Palindrome");
15. }
16. }

Output:

Palindrome

Time complexity: O(n/2)

How will you find smallest element in an array?

Problem statement:
Given an array of positive or negative integer. How will you write an algorithm to find out the largest element in the given array?

1. public class LargestElement {
2. public static void main(String[] args) {
3. int a[] = { 3, 4, 1, 5, 0, -10 };
4. int max = Integer.MIN_VALUE;  //-2147483648
5. for (int i = 0; i < a.length; i++) {
6. if (a[i] > max) {
7. max = a[i];
8. }
9. }
10. System.out.println("max: " + max);
11. }
12. }

Output:

max: 5

How will you find smallest element in an array?

Problem statement:
Given an array of positive or negative integer. How will you write an algorithm to find out the smallest element in the given array?

1. public class SmallestElement {
2. public static void main(String[] args) {
3. int a[] = { 3, 4, 1, 5, 0, -10, -40 };
4. int min = Integer.MAX_VALUE; // 2147483647
5. for (int i = 0; i < a.length; i++) {
6. if (a[i] < min) {
7. min = a[i];
8. }
9. }
10. System.out.println("min: " + min);
11. }
12. }

Output:

min: -40

What do you mean by Association, Aggregation and Composition in Java?

Click here

What is the difference between Hashtable and ConcurrentHashMap

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What is the difference between Hashtable & HashMap?

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What are different ways of creating a thread in java?

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How do you stop a running thread?

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What is heap memory and stack memory in java?

Click here 

Can we overload constructor in java?

Problem statement:
You are given a code for constructor overloading. What do you think, can we overload the constructor in java?

Ans: Yes.

1. class A {
2. A() {
3. System.out.println("default");
4. }
5. A(int id) {
6. System.out.println("id");
7. }
8. A(int id, String name) {
9. System.out.println("id & name");
10. }
11. A(String name, Double salary) {
12. System.out.println("name & salary");
13. }
14. }
15. public class Sample {
16. public static void main(String[] args) {
17. A a = new A();
18. }
19. }

Output:

default

Can we override constructor in java?

Problem statement:
You are given a code for constructor overriding. What do you think, can we override the constructor in java?

Ans: No.

1. class A {
2. A() {
3. System.out.println("A of A");
4. }
5. }
6. class B extends A {
7. A() {
8. System.out.println("A of B");
9. }
10. }
11. public class Sample {
12. public static void main(String[] args) {
13. B b = new B();
14. }
15. }

Output:

Return type of method is missing, meaning compiler is treating A() as a method not as a constructor and also compiler is expecting return type for the method A(), because in code there is no return type.

what will happen when you run the following code?

Problem statement:
Given the java code. what will be the output?

1. public class Test {
2. static void test() throws RuntimeException {
3. try {
4. System.out.println("test");
5. throw new RuntimeException();
6. } catch (Exception ex) {
7. System.out.println("exception");
8. }
9. }
10. public static void main(String[] args) {
11. try {
12. test();
13. throw new RuntimeException();
14. } catch (RuntimeException ex) {
15. System.out.println("runtime");
16. System.out.println("end");
17. }
18. }
19. }

Output:
test
exception
runtime
end

What is the output of the following code?

Problem statement:
Given the code of java. Find out the output.

1. public class Test {
2. static void test() throws RuntimeException {
3. try {
4. System.out.println("test");
5. throw new RuntimeException();
6. } catch (Exception ex) {
7. System.out.println("exception");
8. }
9. }
10. public static void main(String[] args) {
11. try {
12. test();
13. } catch (RuntimeException ex) {
14. System.out.println("runtime");
15. }
16.     System.out.println("end");
17. }
18. }

Output:

test

exception
end

What is the output of the following code?

Problem statement: 
Given the code of java. Can you tell me the output of this?

1. interface Annonymous {
2.     public int getValue();
3. }
4. public class Sample1 {
5.     int data = 15;
6.     public static void main(String[] args) {
7.         Annonymous a = new Annonymous() {
8.             int data = 5;
9.             public int getValue() {
10.                 return data;
11.             }
12.             public int getData() {
13.                 return data;
14.             }
15.         };
16.         Sample1 s = new Sample1();
17.         System.out.println(a.getValue() + a.getData() + s.data);
18.     }
19. }

Output:
compilation error at line number 17 due to a.getData(). Here getData() is not a method of Annonymous interface.

What is the output of the following code?

Problem statement: Given the code of java. Can you tell me the output of this?

1. interface Annonymous {
2.     public int getValue();
3. }
4. public class Sample1 {
5.     int data = 15;
6.     public static void main(String[] args) {
7.         Annonymous a = new Annonymous() {
8.             int data = 5;
9.             public int getValue() {
10.                 return data;
11.             }
12.             public int getData() {
13.                 return data;
14.             }
15.         };
16.         Sample1 s = new Sample1();
17.         System.out.println(a.getValue() + s.data);
18.     }
19. }

Output:

20