Java String Interview Questions and Answers

When it comes to applying for a job in software development, having a good understanding of the String class can be essential for getting hired. Interviewers will often ask you specific questions about the Java String class in order to test your knowledge and ability to solve problems. In this blog article, we will discuss some of the most common Java String interview questions and their corresponding answers.

What is String in Java?

The Java String class is a class in the Java programming language that provides methods for manipulating strings. It allows programmers to manipulate strings in a variety of ways such as searching, replacing, and comparing strings. The Java String class is an immutable class which means that once a string is created, it cannot be changed.

What are some of the methods available in the String class?

The String class provides several methods for manipulating strings. Some of these methods include length(), equals(), replace(), substring(), charAt(), indexOf(), toUpperCase(), and toLowerCase(). These methods provide powerful string manipulation capabilities that allow for more efficient programming.

How can I use the length() method in the Java?

The length() method in the Java String class can be used to determine the length of a string. This method takes in a string and returns the length of that string. For example, if the string “Hello world” is passed into the length() method, the method will return 11.

How can I use the equals() method in the Java String?

The equals() method in the String class can be used to compare two strings for equality. This method takes in two strings and returns a boolean value – true if the two strings are equal, and false if not. For example, if the strings “Hello world” and “Hello world” are passed into the equals() method, the method will return true.

How can I use the replace() method in the Java String?

The replace() method in the String class is used to replace one substring within a string with another substring. This method takes in three arguments – a string to be modified, a substring to be replaced, and a substring to replace the original substring. For example, if the string “Hello world” is passed into the replace() method with the substring “world” to be replaced and “universe” to be used as the replacement, the resulting string will be “Hello universe”.

How can I use the substring() method in the String?

The substring() method in the String class can be used to extract a substring from a string. This method takes in two arguments – a string to be modified, and the index of the first character of the substring to be extracted. For example, if the string “Hello world” is passed into the substring() method with the index 4, the resulting string will be “o world”.

How can I use the charAt() method in the Java String class?

The charAt() method in the Java String class is used to determine the character at a specified index within a string. This method takes in one argument – an index within the string. For example, if the string “Hello world” is passed into the charAt() method with index 6, the resulting character will be ‘w’.

How can I use the indexOf() method in the Java String?

The indexOf() method in the String class is used to determine the index of the first occurrence of a specified character within a string. This method takes in two arguments – a character to search for and an optional starting position. For example, if the string “Hello world” is passed into the indexOf() method with the letter ‘o’, the resulting index will be 4.

How can I use the toUpperCase() method in the Java String?

The toUpperCase() method in the String class is used to convert all of the characters in a string to uppercase. This method takes in no arguments and returns a new string with all of the characters converted to uppercase. For example, if the string “Hello world” is passed into the toUpperCase() method, the resulting string will be “HELLO WORLD”.

How can I use the toLowerCase() method in the Java String?

The toLowerCase() method in the String class is used to convert all of the characters in a string to lowercase. This method takes in no arguments and returns a new string with all of the characters converted to lowercase. For example, if the string “Hello world” is passed into the toLowerCase() method, the resulting string will be “hello world”.

Java String Code Example

In the following example, we will use the String class to search a string for a specified substring. The example code makes use of the indexOf() and substring() methods.

public class Example {
public static void main(String[] args) {
 String text = "Hello world";
 int startIndex = text.indexOf("world");
 System.out.println(text.substring(startIndex));
 }
}

The output of this code will be the string “world”.

Conclusion

Hopefully, this blog article has provided you with a better understanding of the Java String class and Java String Interview Questions. Being able to answer questions about the Java String class in an interview setting can be a great way to show your proficiency in the language and land the job you’re after.

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