String Interview Programs In Java
Top Java Interview Questions on String Manipulation
String Interview Programs in Java are a set of coding exercises that focus on the use of strings in programming. These programs cover various topics such as string manipulation, string comparison, substring operations, and string concatenation. They are designed to showcase the candidate's understanding of string concepts and their ability to write efficient code using string methods and functions. These programs help in evaluating a candidate's problem-solving skills and their understanding of the Java language. Some common string interview programs include palindrome check, string reversal, string compression, and anagram detection.
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1 - Write a Java program to reverse a string: In order to reverse a string in Java, we can use the charAt() method to get the characters at specific indices and append them in reverse order to a new string. Then, we can return the reversed string as the output.
2) Write a Java program to check if a string is a palindrome: To check if a string is a palindrome, we can compare the string with its reverse using the equals() method. If they match, then the string is a palindrome. If not, then it is not a palindrome.
3) Write a Java program to count the frequency of each character in a string: We can use a HashMap to store the characters as keys and their frequency as values. Then, we can iterate through the string and increment the frequency value for each character encountered. Finally, we can print the HashMap to display the frequency of each character.
4) Write a Java program to find the length of the longest substring without repeating characters: This can be achieved by using a sliding window approach. We can use two pointers, one at the beginning and one at the end of the substring. As we iterate through the string, we can keep track of the characters encountered in a HashSet. If a duplicate character is encountered, we move the start pointer to the index after the first occurrence of that character. The length of the longest substring can be calculated by subtracting the start pointer from the end pointer.
5) Write a Java program to find the first non-repeating character in a string: First, we can store the characters and their frequency in a HashMap as mentioned earlier. Then, we can iterate through the string again and check the frequency of each character in the HashMap. The first character with a frequency of 1 will be the first non-repeating character in the string.
6) Write a Java program to remove all the white spaces from a string: Using the replaceAll() method, we can replace all the white spaces in a string with an empty character, thereby removing them.
7) Write a Java program to check if two strings are anagrams: Anagrams are words that contain the same characters but in a different order. To check this, we can first sort the two strings and then compare them using the equals() method. If they are equal, then they are anagrams.
8) Write a Java program to generate all possible permutations of a string: To generate all the permutations of a string, we can use a recursive approach. We can fix one character at a time and then generate permutations for the rest of the characters. Once we have all the permutations, we can print them as the output.
9) Write a Java program to find the first non-repeating character in a string: We can use a LinkedHashMap to store the characters and their frequency. Then, we can iterate through the LinkedHashMap and find the first character with a frequency of 1.
10) Write a Java program to check if two strings are rotation of each other: To check if two strings are rotations of each other, we can concatenate the first string with itself and then check if the second string is a substring of the concatenated string.
11) Write a Java program to find the second highest occurrence of a character in a string: We can use two variables to store the highest and second highest occurrence of characters. Then, we can iterate through the string and update these variables accordingly. Finally, we can print the character with the second highest occurrence.
12) Write a Java program to split a string into equal parts: We can use the substring() method to split the string into equal parts. We can calculate the length of each part by dividing the length of the string by the number of parts required. Then, we can use a loop to extract each part and store it in an array or print it as the output.
13) Write a Java program to find the longest common prefix in a given set of strings: This can be done by comparing the characters at the same index in all the strings and stopping when a mismatch is encountered. The substring till that index will be the longest common prefix.
14) Write a Java program to check if a string is a valid ISBN: In an ISBN, the last digit is a check digit which is calculated based on the previous 9 digits. We can use a loop to calculate the check digit and compare it with the last digit in the ISBN. If they match, then the string is a valid ISBN.
15) Write a Java program to remove duplicates from a string: We can use a HashSet to store the characters in the string. Since Sets do not allow duplicates, we can add each character to the set and then convert it back to a string to remove duplicates. Alternatively, we can use the replaceAll() method to replace duplicates with an empty character.
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