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Java String Interview Questions
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1) Is String a keyword in Java?
2) Is String a primitive type or derived type?
3) In how many ways you can create string objects in Java?
4) What is string constant pool?
5) What is special about string objects as compared to objects of other derived types?
6) What do you mean by mutable and immutable objects?
7) Which is the final class in these three classes – String, StringBuffer and StringBuilder?
8) What is the difference between String, StringBuffer and StringBuilder?
9) Why StringBuffer and StringBuilder classes are introduced in Java when there already exist String class to represent the set of characters?
10) How many objects will be created in the following code and where they will be stored in the memory?
String s1 = "abc";
String s2 = "abc";
11) How do you create mutable string objects?
12) Which one will you prefer among “==” and equals() method to compare two string objects?
13) Which class do you recommend among String, StringBuffer and StringBuilder classes if I want mutable and thread safe objects?
14) How do you convert given string to char array?
15) How many objects will be created in the following code and where they will be stored?
String s1 = new String("abc");
String s2 = "abc";
16) Where exactly string constant pool is located in the memory?
17) I am performing lots of string concatenation and string modification in my code. which class among string, StringBuffer and StringBuilder improves the performance of my code. Remember I also want thread safe code?
18) What is string intern?
19) What is the main difference between Java strings and C, C++ strings?
20) How many objects will be created in the following code and where they will be stored?
String s1 = new String("abc");
String s2 = new String("abc");
21) Can we call String class methods using string literals?
22) do you have any idea why strings have been made immutable in Java?
23) What do you think about string constant pool? Why they have provided this pool as we can store string objects in the heap memory itself?
24) What is the similarity and difference between String and StringBuffer class?
25) What is the similarity and difference between StringBuffer and StringBuilder class?
26) How do you count the number of occurrences of each character in a string?
27) How do you remove all white spaces from a string in Java?
28) How do you find duplicate characters in a string?
29) Write a Java program to reverse a string?
30) Write a Java program to check whether two strings are anagram or not?
31) Write a Java program to reverse a given string with preserving the position of spaces?
32) How do you convert string to integer and integer to string in Java?
33) Write a code to prove that strings are immutable in Java?
34) Write a code to check whether one string is a rotation of another?
35) Write a Java program to reverse each word of a given string?
36) Print all substrings of a string in Java?
37) Print common characters between two strings in alphabetical order in Java?
38) How find maximum occurring character in a string in Java?
39) What is difference between Java 8 StringJoiner, String.join() and Collectors.joining()?
40) How to reverse a sentence word by word in Java?