String Programming Interview Questions In Java
String Programming Interview Questions in Java
String programming interview questions in Java typically revolve around the manipulation, comparison, and creation of string objects in Java. These questions may require knowledge of string methods, such as length(), charAt(), and substring(), as well as understanding of string immutability and the differences between String, StringBuffer, and StringBuilder classes. Interviewers may also ask about ways to optimize string manipulation in Java, such as using StringBuilder instead of concatenation. It is important for candidates to have a strong understanding of strings and their usage in Java, as they are widely used in programming and can greatly impact the performance of an application.
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1 - What is the difference between String and StringBuffer in Java?
String is an immutable class, which means that once a string object is created, its value cannot be changed. StringBuffer, on the other hand, is a mutable class, which allows for modification of its contents. This makes StringBuffer more efficient for tasks such as concatenation or appending.
2) How can you reverse a string in Java without using any built-in functions?
One approach is to use a loop to iterate through the characters of the string and append them to a new string in reverse order. Another approach is to convert the string to an array of characters, then use a for loop to swap the characters from the beginning and end of the array.
3) Explain the difference between equals() and == in Java.
The == operator checks for object equality, meaning it checks if two objects refer to the same memory location. The equals() method, on the other hand, checks for value equality, meaning it compares the actual contents of the objects. While == can be used to compare primitive types, equals() should be used for comparing objects.
4) How can you check if a string contains a specific substring in Java?
You can use the contains() method, which returns a boolean value based on whether the string contains the specified substring. Another option is to use the indexOf() method, which returns the index of the first occurrence of the substring within the string, or -1 if it is not found.
5) What is the difference between final, finally, and finalize in Java?
The final keyword is used to indicate that a variable, method, or class cannot be changed or extended. The finally block is used in exception handling to ensure that a block of code is executed regardless of whether an exception is thrown. The finalize() method is called by the garbage collector when an object is about to be destroyed.
6) How can you convert a string to an int in Java?
You can use Integer.parseInt() to convert a string to an int. This method throws a NumberFormatException if the string cannot be converted to an int. Alternatively, you can use Integer.valueOf() which returns an Integer object rather than a primitive int.
7) What is the StringBuilder class in Java?
StringBuilder is a mutable, thread-safe class that can be used for creating and manipulating strings without the overhead of creating new objects. It is similar to the StringBuffer class, but is not synchronized, making it more efficient for single-threaded scenarios.
8) How can you remove all white spaces from a string in Java?
You can use the replaceAll() method with a regular expression to replace all white spaces with an empty string. For example, str = str.replaceAll("\\s", “”) will remove all white spaces from the string str.
9) How does the String pool work in Java?
The String pool is a special memory area in the JVM where string literals are stored. When a string literal is created, the JVM first checks the pool to see if an equivalent string already exists. If it does, the existing string is returned rather than creating a new object. This saves memory and improves performance.
10) How can you compare two strings lexicographically in Java?
You can use the compareTo() method, which compares two strings based on their natural ordering. It returns a positive integer if the first string is greater, a negative integer if the first string is smaller, and 0 if the strings are equal. Alternatively, you can use the compareToIgnoreCase() method to compare strings regardless of case sensitivity.
11) What is an anagram and how can you check if two strings are anagrams in Java?
An anagram is a word or phrase that is formed by rearranging the letters of another word or phrase. To check if two strings are anagrams, you can first convert them to character arrays, then sort the arrays and compare them. If the sorted arrays are equal, then the strings are anagrams.
12) How can you remove a particular character from a string in Java?
One approach is to use the replace() method, passing in the character you want to remove and an empty string as arguments. Another option is to use the substring() method, passing in the indices of the characters you want to keep.
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13) What is the difference between a StringBuilder and a StringBuffer?
StringBuilder and StringBuffer are both mutable string classes, but StringBuffer is synchronized while StringBuilder is not. This makes StringBuilder more efficient for single-threaded scenarios, while StringBuffer is better suited for multi-threaded environments.
14) How can you convert a char to a String in Java?
You can use the valueOf() method in the String class, passing in the char as an argument. Alternatively, you can concatenate the char with an empty string, as in str = ch + “”. Both methods will return a string representation of the char.
15) What is a palindrome and how can you check if a string is a palindrome in Java?
A palindrome is a word, phrase, or sequence that reads the same backward as forward. To check if a string is a palindrome, you can first reverse the string and compare it to the original. If they are equal, then the string is a palindrome. Alternatively, you can use a loop to compare the characters from the beginning and end of the string. If they are ever not equal, then the string is not a palindrome.
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