Java String Interview Questions

In core Java, String is one of the key class for understanding the start of basic java programming. The string class is well defined and holds in java.lang package. It is an immutable class, so the developer can use it directly without creating an instance every time.

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If you are looking for a job related to Java String, you need to prepare for the 2023 Java String Interview Questions. Every interview is indeed different as per the different job profiles. Here, we have prepared the important Java String Interview Questions and Answers which will help you succeed in your interview.

In this article, we shall present the 10 most important and frequently asked Java String Interview Questions. These questions are divided into two parts are as follows:

Part 1 – Java String Interview Questions (Basic)

This first part covers basic Java String Interview Questions and Answers

Q1. Explain in details about the class String in a Java programming language how one developer can use the same. Should we consider the String in a Java programming language as a data type? If yes, please explain in detail?

Answer:

A string is one of the key class in Java, and it basically holds in java.lang package. It is not at all define as primitive data types like other variables of Java int or long. It mainly holds a lot of character strings in a single representation. String object is very much popular in java programming for using almost all the coding from starting to end, it is an immutable and final class defined in the Java core package, and JVM normally created one String pool for storing all the created String object.

Q2. In a Java programming language, there are various approaches available to create an object of String; explain in detail the approaches available for creating the same, and give some related example with a code snippet?

Answer:

There are several ways a developer can create a String object in a Java programming language. Approaches are below:

• Using New operator: We can create one string object by using a simple new operator like other object creation, but it will not store in the String pool of JVM.
• Using “operator: String object can create by just using “ operator and provide the corresponding value inside it. The utility of the same, JVM considers that value to store in String pool and return accordingly.
• Using others: Possible to create a string object from a byte array, char array, StringBuilder or StringBuffer.

String str = new String("abcd"); à not store in JVM String pool
String str1 = "abcd"; à store in JVM String pool

Let us move to the next Java String Interview Questions

Q3. The one keyword is very much used in Java language called ‘Palindrome’. Please explain when one string object reference in Java programming can call as ‘Palindrome’, is it possible to write a java method for checking the same? If yes, please give some example with a code snippet.

Answer:

One String object can be called as ‘Palindrome’ when the value of that specific String class can be the same when it will be reversed. As an example, we can say like ‘cbc’, here this string value can be considered as Palindrome, as a reverse of this value will always provide the same result.

Normally two popular approaches available for validating the same in String, based on the interviewer expectation, we can rely on the same:

• StringBuilder strBuilder = new StringBuilder(“cbc”);

strBuilder.reverse();

• String str1 = “abc”;

Int lenStr1 = str1.length();
For(int j=0; j< lenStr1/2; j++){
If(str1.charAt(j) != str1.charAt(lenStr1 – j-1)){
Return false;
}
}

Return true;

Q4. Suppose you want to remove some asci characters or provide or given character from one of the String objects defined in a Java programming language; how you can do this by using one single method in Java Programming. Please explain with a code snippet?

Answer:

These are the basic Java String Interview Questions asked in an interview. One of the key methods we normally used to replace the entire string is the replace All method. It will help the developer for replacing the entire content of the String with another String content as per the requirement of the project. But one of the key characteristics of a replacement. All method is it always accepting String as it’s one of the specific arguments, so it will very much require for using one of the Character classes for creating the string and use the same properly for replacing it with another expected String or an empty string. Please find below the code snippet with an example.

public String replaceString(String str1, char c1){
Return str1.replaceAll(Character.toString(c1), "……");
}

Q5. One of the very common requirements in a programming language is to make some property in upper case or lower case. Is there any specific methodology defined for String object in a Java programming language to present that property value in upper case or lower case? Please explain with a code snippet?

Answer:

It will be one of the very common functionalities required for the developer in any case for the String object variable value. A developer can easily be used to UpperCase and LowerCase methods on the specific String class to getfor getting the entire string value in total upper case or total lower case. This method has one more optional argument, which is a locale object. So someone can able to use some specific locale rules for making the string value in upper case or lower case.

String s = "abc";
String s1 = "ABC"
System.out.println("Upper case of S: "+s.toUpperCase()+", lower case of S1: "+s1.toLowerCase());

Part 2 – Java String Interview Questions (Advanced)

Let us now have a look at the advanced Java String Interview Questions.

Q6. Is there any method in String call subsequence? If yes, please explain the same in details with a proper definition?

Answer:

CharSequence interface is a very much useful interface in java introduce to Java 1.4. The string class normally implements that specific interface. So the implementation of the subsequence method inside the String class can be possible due to the above reason. Actually, it invokes one of the frequent methods of String called the substring method internally.

Q7. One another very common requirement for the developer in Java programming is to compare two objects as per development requirements. Is it possible to compare two String object in the Java programming language? If yes, please explain how it can be done?

Answer:

Comparing between two String values can be done by below approaches:

• Using a comparable interface: Java String normally implements a comparable interface, so compare To method can be utilized easily to compare two string values.
• By using equals or equalsIgnoreCase method: String value can be compared easily by using direct method equal or eualsIgnoreCase.

Let us move to the next Java String Interview Questions

Q8. Is it possible to convert one of the String objects into a char data type or one char data type covert to a String object? If yes, please explain how it can be achievable?

Answer:

charAt method can be used to get an individual character by providing an index, and the CharAraay method converts one string value to a character array.

String str = "abc";
Char c = str.charAt(0);
String str1 = new String("This is a test String");
char[] carray= str1.toCharArray();
for(char c1: carray){
System.out.print(c1);
}

Q9. One of the very popular methodologies in the Java programming language called the switch case. Is it possible to use switch case methodology in case of using String object for java programming? If yes, please explain how it can be possible?

Answers:

This is the most asked Java String Interview Question in an interview. Switch case is one of the common functionality for avoiding writing a lot of if-else logic in the entire code. It always helps in maintaining code quality properly. Earlier switch case reference only is able to do for the integer or long values only. But from the Java 7 version onwards, java allows using switch case on String object as well. So as of now, the String value can be used for switch case utility.

Q10: Suppose planning to perform every kind of permutation of String class in java programming. Please give some details programming of how we can able to do this by using String object properly?

Answer:
We can use this by using the below code:

Set perm = new HashSet();
char initial = str.charAt(0);
String rem = str.substring(1);
Set words = permutationFinder(rem);
for (String strNew : words) {
for (int i = 0;i<=strNew.length();i++){
perm.add(charInsert(strNew, initial, i));
}
}
return perm;
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