Core Java - Interview Questions and Answers for 'Oding' | Search Interview Question

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Q91. Write a Program to validate an email address

Ans. public class Class{
public static void main(String[] args){
String str = "xyz@123.com";

if(!str.contains("@") && !str.contains(".") && (str.indexOf('.') < str.indexOf('@'))){
System.out.println("Not a Valid Email Address");
}
}
}

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Q92. Write a Program to validate if a particular character occurs after another in a string

Core Java

Ans. public class Class{
   public static void main(String[] args){
      String str = "xyz123.co@m";

      if(str.indexOf('.') < str.indexOf('@')){
         System.out.println("Not a Valid Email Address");
      }
   }
}

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Q93. How to find the median number in an array of integers ?

Core Java

Ans.

Arrays.sort(numArray);
double median;
if (numArray.length % 2 == 0)
median = ((double)numArray[numArray.length/2] (double)numArray[numArray.length/2 - 1])/2;
else
median = (double) numArray[numArray.length-1/2];

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Q94. Write a Java program to print 10 random numbers between 1 to 100?

Core Java

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Q95. Write a method / program that will determine if the parenthesis are balanced in a given string.

Core Java

Ans. https://www.geeksforgeeks.org/check-for-balanced-parentheses-in-an-expression/

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Q96. Given array of integers, find first two numbers that adds up to 10.

Core Java

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Q97. Write a program to reverse words of a sentence.

Core Java

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Q98. Implement stack using generics in Java.

Data Structure

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Q99. How can you extract integers from string values and add (sum it up) all the extracted integers? e.g "James34long4island322in3rdAvenue" ---> 34 4 322 3 = 363

Core Java

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Q100. Write a Program to convert a binary to number ?

Core Java

Ans. int convert(int binaryInt) {
int sumValue=0;
int multiple = 1;
while(binaryInt > 0) {
binaryDigit = binaryInt;
binaryInt = binaryInt /10;
sumValue = sumValue (binaryDigit * multiple);
multiple = multiple * 2;
}

return sumValue;
}

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Q101. Given a string with multiple opening and closing brackets, determine if the string is valid or not ( to see if the string has all closing brackets for each opening bracket ) ?

Core Java

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Q102. Write a method, that compare two numbers and return the bigger one ?

Core Java

Ans. int compare(int a, int b) {
a>b? return a: return b;
}

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Q103. Write a Program for insertion sort.

Core Java

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Q104. How to calculate lcm of two numbers ?

Core Java

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Q105. Write a Program to find age by birth date ?

Core Java

Ans. LocalDate today = LocalDate.now();
LocalDate birthday = LocalDate.of(1960, Month.JANUARY, 1);
Period p = Period.between(birthday, today); //Now access the values as below
System.out.println(period.getDays());
System.out.println(period.getMonths());
System.out.println(period.getYears());

Sample Code for LocalDate

Sample Code for Period

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Q106. What will be the output of following code

class TestMain {
public static void main(String[] args) {
String s1 = "ravi";
String s2 = new String("ravi");
Integer i = 10;
Integer a1 = new Integer("10");
System.out.println(s1 == s1);
System.out.println(i == a1);
}
}

Core Java

Ans. false
false

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Q107. Write a Program to check if the entered number is a Duck Number ( Number having 0 in it ) ?

Core Java

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Q108. Suppose we have a string "Java is object oriented language" and we have to reverse every alternate word in string. How would we do that using Java program.

Core Java

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Q109. A Kid can go up 1, 2 or 3 stairs in one step. Write a method that takes number of steps in a stair will print all possible ways he can take.

For example , printAllCombinations(3) should print

111
12
21
3

Similarly , printAllCombinations(4) should print

1111
121
13
211
22
31
4

Core Java

Ans. public static String findStep(int n) {
if (n == 1 || n == 0)
return 1;
else if (n == 2)
return 2;
else
return findStep(n - 3) + findStep(n - 2) + findStep(n - 1);
}

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Q110. Write an efficient program for printing k largest elements in an array. Elements in array can be in any order.

Data Structure

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Q111. Create a custom hashmap using synchronization.

Core Java

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Q112. Write a Program to find number of lines , words and characters in a File.

Core Java

Ans. import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class FileUtility {

public static void main(String[] args) {
System.out.println(printFile("/home/userme/notes"));
}

private static int printFile(String filePath) {
int wordCount = 0;
try (BufferedReader br = new BufferedReader(new FileReader(filePath))) {
String line = null;
String[] wordsArray = null;

while ((line = br.readLine()) != null) {
wordsArray = line.split(" ");
wordCount = wordsArray.length;
}
} catch (IOException e) {
e.printStackTrace();
}
return wordCount;

}
}

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Q113. Write code to get count of every 5 letter word in a string using lambda expression

Core Java

Ans. String str = "I had been saying that he had been there";

Map<String,Long> countWords = Arrays.asList(str.split(" ")).stream().filter(p->p.length() = 5).collect(Collectors.groupingBy(p->p,Collectors.counting()));

System.out.println(countWords);

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Q114. Find Intersection/union between two arrays.

Core Java

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Q115. Design a Program to clone an object and all it's children.

Design

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Q116. Given a String with letters , numbers and special characters , extract Tokens from it. The rules for Token extraction are ac follows

1. Should for token of all characters till a number or special character is found
2. Should form token of all numbers till a character or special character is found
3. Special character in itself is a token
4. Ignore white spaces

For example - Bob Said "He is here"

should result in

Bob A
Said A
" S
He A
is A
here A
" S

where a is specifying alphabet and S as special character

Design

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Q117. How many bytes a character takes with UTF-8 encoding ?

Encoding

Ans. it takes 1 to 4 bytes

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Q118. How to calculate string length without using inbuilt function

Core Java

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Q119. in the following class:
class A {
void methoda(Object o) {
Sysout("Object");
}

void methoda(String s) {
Sysout("String");
}

public static void main(String []args) {
A a = new A();
a.methoda(null);
}
}

what will be printed?

Core Java

Ans. String

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Q120. Can you share your experience with encoding and encryption ?

Encoding

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