How do you install Intellij IDEA on Ubuntu?

Problem statement: How do you install intellij IDE on Ubuntu?

$> sudo apt-add-repository ppa:mmk2410/intellij-idea 

$> sudo apt-get update

• The community edition can then installed with

$> sudo apt-get install intellij-idea-community

• and the ultimate edition with

$> sudo apt-get install intellij-idea-ultimate

Saving data to file using SpringBoot postman

pom.xml:
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>

<groupId>com.boot</groupId>
<artifactId>raja-boot</artifactId>
<version>1.0.1-Release</version>
<packaging>war</packaging>

<name>spring-boot</name>
<url>http://maven.apache.org</url>

<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<java.version>1.8</java.version>
</properties>

<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.5.1.RELEASE</version>
</parent>

<dependencies>

<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<!-- <dependency> -->
<!-- <groupId>org.springframework.boot</groupId> -->
<!-- <artifactId>spring-boot-starter-data-jpa</artifactId> -->
<!-- </dependency> -->

<!-- https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-starter-json -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-json</artifactId>
<version>2.0.3.RELEASE</version>
</dependency>

</dependencies>
<build>
<plugins>
<!-- Package as an executable jar/war -->
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>

2. SpringBootApp.java
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication(scanBasePackages={"com.boot"})
public class SpringBootApp {

public static void main(String[] args) {
SpringApplication.run(SpringBootApp.class, args);
System.out.println("spring boot application is running");
}
}

3. RestController.java

import java.io.BufferedWriter;

import java.io.File;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.OutputStreamWriter;

import org.springframework.web.bind.annotation.RequestBody;

import org.springframework.web.bind.annotation.RequestMapping;

import org.springframework.web.bind.annotation.RequestMethod;

import org.springframework.web.bind.annotation.ResponseBody;

import com.boot.entity.Student;

@org.springframework.web.bind.annotation.RestController

@RequestMapping("/api")

public class RestController {

@RequestMapping(value = "/ping/", method = RequestMethod.GET)

public String ping() {

  return "successsss !!";

}

@RequestMapping(value = "/create/", method = RequestMethod.POST)

@ResponseBody 

public String create(@RequestBody Student data) throws IOException {

File file = new File("/home/rajar/demo.txt");

FileOutputStream stream = new FileOutputStream(file);

OutputStreamWriter obj = new OutputStreamWriter(stream);

BufferedWriter br  =new BufferedWriter(obj);

br.write(data.getName().toString());

br.append("\n");

br.write(data.getId());

br.close();

  return "<h2>rajjjjjjaaaaaa !!</h2>";

}

}

4. Student.java

import java.io.Serializable;

public class Student implements Serializable {

private String id;

private String name;

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public String getId() {

return id;

}

public void setId(String id) {

this.id = id;

}

}

How do you print all elements of a matrix in diagonal order?

Problem statement: 

Print Matrix Diagonally (Diagonal order)

How do you find largest element in an array ?

Problem statement: how do you find the largest element in an array?

Method-I:

1. public class LargestElementInArray{
2. public static void main(String[] args) {
3. int a[] = { 60, 65, 70, 55, 45, 80 };
4. int max = a[0];
5.   int length = a.length;
6. for(int i=0; i<length; i++){
7. if(max < a[i]){
8. max = a[i];
9. }
10. }
11. System.out.println(max);
12. }
13. }

Output: 80
Time complexity: O(n)

Method-II:

1. public class LargestElementInArray {
2. public static void main(String[] args) {
3. int a[] = { 60, 65, 70, 55, 45, 80 };
4. int max = a[0];
5. int length = a.length;
6. int end = a.length - 1;
7. for (int i = 0; i < length / 2; i++) {
8. if (max < a[end]) {
9. max = a[end];
10. }
11. if (max < a[i]) {
12. max = a[i];
13. }
14. }
15. System.out.println(max);
16. }
17. }

Output: 80
Time complexity: O(n/2)

How do you declare, instantiate, initialize and traverse an array?

Problem statement: How will you declare, initialize & traverse an array?

1. class TestArray {
2. public static void main(String args[]) {
3. int a[] = new int[5];// declaration and instantiation.
4. a[0] = 10;// initialization.
5. a[1] = 20;
6. a[2] = 70;
7. a[3] = 40;
8. a[4] = 50;
9. }
10. }

Longest Palindromic Substring

Problem statement: Given a string s, find the longest palindromic substring in s. You may assume that the maximum length of s is 1000.

1. import java.io.IOException;
2. public class LongestSubstringPalindrome
3. {
4.   public static void main(String[] args) throws IOException
5.   {
6.     // String word = "abbcbba";
7.     String str = "abbagoodteacher";
8.     System.out.println(longestPalindrome(str));
9.   }
10.   public static String longestPalindrome(String s)
11.   {
12.     int length = s.length();
13.     if (s == null || length < 2)
14.     {
15.       return s;
16.     }
17.     boolean isPalindrome[][] = new boolean[length][length];
18.     int left = 0;
19.     int right = 0;
20.     for (int j = 1; j < length; j++)
21.     {
22.       for (int i = 0; i < j; i++)
23.       {
24.         boolean isInnerWordPalindrome = isPalindrome[i + 1][j - 1] || j - i <= 2;
25.         if (s.charAt(i) == s.charAt(j) && isInnerWordPalindrome)
26.         {
27.           isPalindrome[i][j] = true;
28.           if (j - i > right - left)
29.           {
30.             left = i;
31.             right = j;
32.           }
33.         }
34.       }
35.     }
36.     return s.substring(left, right + 1);
37.   }
38. }

Output: abba

Best time to buy & sell stock

Problem statement: Say you have an array for which the i-th element is the price of a given stock on day i .

If you were only permitted to complete at most one transaction (i.e. buy one &  sell one share of the stock), design an algorithm to find the maximum profit.

Example:
Input:  [7, 3, 6, 7, 2, 8, 5, 6]
Output: 
max difference: 8-2 = 6

1. public class BuySellStock
2. {
3.   public static void main(String[] args)
4.   {
5.     int p[] =  { 7, 3, 6, 7, 2, 8, 5, 6 };
6.     System.out.println(maxProfit(p));
7.   }
8.   static int maxProfit(int[] prices)
9.   {
10.     int maxProfit = 0;
11.     int minPrice = Integer.MAX_VALUE;
12.     for (int i = 0; i < prices.length; i++)
13.     {
14.       minPrice = Math.min(minPrice, prices[i]);
15.       maxProfit = Math.max(maxProfit, prices[i] - minPrice);
16.     }
17.     return maxProfit;
18.   }
19. }

Output: 6

How do you do search in an array where difference between adjacent elements is k

Problem statement: How do you do efficient search in an array where difference between adjacent elements is k

1. public class JumpSearchWithKDiff {
2. public static void main(String[] args) {
3. int a[] = { 2, 4, 6, 8, 6, 4, 2, -1, -3 };
4. int s = -3; // 's' is the element to be searched
5. int k = 2; // diff. b/w element
6. int n = a.length; // length of array
7. System.out.println("Element " + s + " is present at index " + searchAlgo(a, n, s, k));
8. }
9. static int searchAlgo(int a[], int n, int s, int k) {
10. // scan the given array staring from leftmost element
11. int i = 0;
12. while (i < n) {
13. // check if element is found
14. if (a[i] == s)
15. return i;
16. // else jump to diff. b/w current array element & search element
17. // divided by k We use max here to make sure that i moves at-least one step ahead
18. i = i + Math.abs(a[i] - s) / k;
19. // i = i + Math.max(1, Math.abs(a[i] - s) / k);
20. }
21. System.out.println("number is " + "not present!");
22. return -1;
23. }
24. }

Output:

Element -3 is present at index 8

How do you do search in an array where difference between adjacent elements is always 1

Problem statement: How do you do efficient search in an array where difference between adjacent elements is always 1

1. public class JumpSearch {
2. public static void main(String[] args) {
3. int a[] = { 9, 10, 11, 12, 11, 10, 9, 8, 7, 6, 7, 8, 9, 8, 7, 6, 5};
4. System.out.println(searchAlgo(a, 7)); // search element is 7
5. }
6. // 's' is the element to be searched in array a[0..n-1]
7. static int searchAlgo(int a[], int s) {
8. int n = a.length; // length of array
9. // scan the given array staring from leftmost element
10. int i = 0; // left first index
11. while (i < n) {
12. // check if element is found
13. if (a[i] == s) {
14. return i;
15. }
16. // else jump to diff. b/w current array element & search element
17. i = i + Math.abs(a[i] - s);
18. }
19. return -1; // element does not found
20. }
21. }

Output: 8

Time complexity: less than O(n)

How do you print Fibonacci series?

Problem statement: How do you print Fibonacci series?

Def: A series of numbers in which each number ( Fibonacci number ) is the sum of the two preceding numbers.

1. public class FibonacciSeries {
2. public static void main(String[] args) {
3. int count = 10;
4. printFibonacci(count);
5. }
6. public static void printFibonacci(int count) {
7. int a = 0, b = 1, c = 0;
8. System.out.print(a + " " + b + " ");
9. for (int i = 2; i < count; i++) {
10. c = a + b;
11. a = b;
12. b = c;
13. System.out.print(c + " ");
14. }
15. }
16. }

Output: 

0 1 1 2 3 5 8 13 21 34

Method-II:

1. public class FibonacciSeries {
2. public static void main(String[] args) {
3. fibonacci(10); // 10 is count 
4. }
5. public static void fibonacci(int n) {
6. int a[] = new int[n];
7. a[0] = 0;
8. a[1] = 1;
9. System.out.print(a[0] + " " + a[1] + " ");
10. for (int i = 2; i < n; i++) {
11. a[i] = a[i - 1] + a[i - 2];
12. System.out.print(a[i] + " ");
13. }
14. }
15. }

Output:

0 1 1 2 3 5 8 13 21 34

How do you change branch name in git

step-1: go to codebase
step-2: open terminal
step-3: git branch -m new_branch_name

How do you print Odd Even using Thread ?

Problem Statement: How will print Odd Even using Thread?

OR

How will you print t1 & t2 alternatively using thread?

1. import java.util.concurrent.atomic.AtomicLong;
2. class Even extends Thread {
3. AtomicLong num;
4. Object lock;
5. Even(AtomicLong num, Object lock) { // constructor
6. this.num = num;
7. this.lock = lock;
8. }
9. public void run() {
10. synchronized (lock) {
11. while (true) { // infinite loop
12. if (num.get() % 2 != 0) {
13. try {
14. lock.wait();
15. } catch (InterruptedException e) {
16. e.printStackTrace();
17. }
18. } else {
19. System.out.println("even: " + num);
20. try {
21. Thread.sleep(1000);
22. } catch (InterruptedException e) {
23. e.printStackTrace();
24. }
25. num.incrementAndGet();
26. lock.notifyAll();
27. }
28. }
29. }
30. }
31. } // end of Even class
32. 
    
33. class Odd extends Thread {
34. AtomicLong num;
35. Object lock;
36. Odd(AtomicLong num, Object lock) { // constructor
37. this.num = num;
38. this.lock = lock;
39. }
40. public void run() {
41. synchronized (lock) {
42. while (true) { // infinite loop
43. if (num.get() % 2 == 0) {
44. try {
45. lock.wait();
46. } catch (InterruptedException e) {
47. e.printStackTrace();
48. }
49. } else {
50. System.out.println("odd: " + num);
51. try {
52. Thread.sleep(1000);
53. } catch (InterruptedException e) {
54. e.printStackTrace();
55. }
56. num.incrementAndGet();
57. lock.notifyAll();
58. }
59. }
60. }
61. }
62. } // end of Odd class
63. 
    
64. public class EvenOddByThread {
65. public static void main(String[] args) {
66. AtomicLong num = new AtomicLong(1);
67. Object lock = new Object();
68. Odd odd = new Odd(num, lock);
69. Even even = new Even(num, lock);
70. even.start();
71. odd.start();
72. }
73. } // end of EvenOddByThread class

Note: To print t1 & t2 alernatively, just replace the S.O.P. stmt with t1 & t2

Output: 

odd: 1

even: 2

odd: 3

even: 4

odd: 5

even: 6

odd: 7

even: 8

odd: 9

even: 10

How do you do binary search in java?

Problem statement: How will you do for binary search in java?

1. public class BinarySearchExe {
2. public static void main(String[] args) {
3. int a[] = { 2, 4, 5, 6, 7, 9, 10 };
4. int idx = binarySearch(a, 10);
5. System.out.println(idx);
6. } // end of main
7. static int binarySearch(int a[], int key) {
8. int start = 0, end = a.length - 1;
9. while (start <= end) {
10. int mid = (start + end) / 2;
11. if (key == a[mid]) {
12. return mid;
13. } else if (key > a[mid]) {
14. start = mid + 1;
15. } else {
16. end = mid - 1;
17. }
18. }
19. return -1; // if key does not found, return -1
20. } // end of binarySearch method
21. }

Output: 6

How do you create tree data structure ?

Problem statement: How will you create tree in java?

1. /* Class containing left and right child of current
2. node and data value*/
3. class Node
4. {
5. int data;
6. Node left, right;
7. 
   
8. public Node(int data1)
9. {
10. data = data1;
11. left = right = null;
12. }
13. }
14. 
    
15. // A Java program to introduce Binary Tree
16. class BinaryTree
17. {
18. // Root of Binary Tree
19. Node root;
20. 
    
21. // Constructors
22. BinaryTree(int data1)
23. {
24. root = new Node(data1);
25. }
26. 
    
27. BinaryTree()
28. {
29. root = null;
30. }
31. 
    
32. public static void main(String[] args)
33. {
34. BinaryTree tree = new BinaryTree();
35. 
    
36. /*create root*/
37. tree.root = new Node(1);
38. 
    
39. /* following is the tree after above statement
40.  
41.               1
42.             /   \
43.           null  null     */
44. 
    
45. tree.root.left = new Node(2);
46. tree.root.right = new Node(3);
47. 
    
48. /* 2 and 3 become left and right children of 1
49.                1
50.              /   \
51.             2      3
52.           /    \    /  \
53.         null null null null  */
54. 
    
55. 
    
56. tree.root.left.left = new Node(4);
57. tree.root.left.left.right = new Node(9);
58.         /* 4 becomes left child of 2
59.                     1
60.                 /       \
61.                2          3
62.              /   \       /  \
63.             4    null  null  null
64.            /   \
65.           null 9
66.          */
67. System.out.println(tree.root.right.data);
68. }
69. }

Output: 3