JAVA STRING

Question 1

In Java, the ____ class is used to
represent a ___________.

Answer 1

String, group of characters

Question 2

It is one of the most frequently
used classes in Java programming.

Answer 2

Java String or String

Question 3

When a new ____ is created,
________ is allocated for it.

Answer 3

string, memory

Question 4

It is created using double quotes and it can store in the String Pool

Answer 4

String Literals

Question 5

This can be created using the new keyword or concatenation.

Answer 5

Dynamically Constructed Strings

Question 6

What is String Pool

Answer 6

a special memory area.

Question 7

What is Heap

Answer 7

general memory area for objects.

Question 8

The _____ is like a __________ where Java stores data

Answer 8

Heap, large warehouse

Question 9

What are the two key features of Heap Memory?

Answer 9

Dynamic and Garbage Collection

Question 10

Java automatically removes unused data to free up memory.

Answer 10

Garbage Collection

Question 11

A special area within the Heap for storing strings.

Answer 11

String Pool (String Constant Pool)

Question 12

What is the Purpose of String Pool?

Answer 12

Saves memory by reusing identical strings and it Improves performance by avoiding duplicate data.

Question 13

Heap is a general memory for _____, ______, and managed by _______.

Answer 13

data, dynamic, garbage collection

Question 14

String Pool is a ________ for strings, optimized for ______ and ______.

Answer 14

special memory, reuse, efficiency

Question 15

Strings in Java are _________, meaning their values __________ after creation.

Answer 15

immutable, cannot be changed

Question 16

This behavior can lead to __________, especially when performing frequent __________.

Answer 16

higher memory usage, string
manipulations

Question 17

Java’s __________ efficiently manages memory by cleaning up _________.

Answer 17

garbage collector, unused string data

Question 18

In Java, __________ ensures ________ and ________, especially when multiple parts of a program use the same text.

Answer 18

immutability, predictable, safe behavior

Question 19

_________ ensures that multiple threads can access shared _____ without causing _____ or _______.

Answer 19

Thread safety, data, errors, corruption

Question 20

What is race condition?

Answer 20

two threads updating the same data simultaneously.

Question 21

What is data inconsistency?

Answer 21

threads seeing incorrect or partial data.

Question 22

What are the use of Single-Thread?

Answer 22

Perform one task at a time and Slower for multiple tasks.

Question 23

What are the use of Multi-Threaded Programs?

Answer 23

Perform multiple tasks simultaneously. Faster and more efficient.

Question 24

When to use Single-Thread?

Answer 24

Use single-thread for simple programs

Question 25

When to use multi-thread?

Answer 25

Use multi-thread for complex programs

Question 26

In Java, a ________ is a special method used for __________.

Answer 26

constructor, initialization

Question 27

A constructor sets up the _________ by _________ or ___________.

Answer 27

initial state, assigning values, allocating memory,

Question 28

In terms of StringBuilder, a __________is used to ________ a new StringBuilder with a ________ or ___________.

Answer 28

StringBuilder, constructor initialize, default, specified value

Question 29

The StringBuilder class provides several________ that allow different ways to create a _________.

Answer 29

constructors, StringBuilder instance

Question 30

When using StringBuilder() (Default Constructor), what does it initializes?

Answer 30

an empty StringBuilder with a default capacity of 16 characters.

Question 31

When using StringBuilder(int capacity) (Custom Capacity), What does it create?

Answer 31

a StringBuilder with a custom capacity (useful when handling large strings to reduce memory reallocation).

Question 32

When using StringBuilder(String str) (Initialize with String), What does it create?

Answer 32

a StringBuilder initialized with the given string value with the initial capacity of 16+length of the string.

Question 33

When using StringBuilder(CharSequence seq) (Initialize with CharSequence), What does it create?

Answer 33

CharSequence is a general representation of character sequences (like String and StringBuffer).

Question 34

This constructor allows initializing a StringBuilder using a StringBuffer or another CharSequence.

Answer 34

StringBuilder(CharSequence seq) (Initialize with CharSequence)

Question 35

The _________ class in Java provides various _________ to manipulate ________ efficiently.

Answer 35

StringBuilder, methods, string sequences

Question 36

This method adds the specified text at the end of the existing StringBuilder content.

Answer 36

append(String s)

Question 37

The _______ method returns the same _________, allowing ____________.

Answer 37

append(), StringBuilder instance, method chaining

Question 38

This method Inserts the specified text at the given index (offset).

Answer 38

StringBuilder.insert(int offset, data);

Question 39

The index position where the data should be inserted.

Answer 39

offset

Question 40

The value to be inserted (can be a String, char, int, double, etc.).

Answer 40

data

Question 41

The _______ method modifies the existing ________ data without creating a new one.

Answer 41

insert(), StringBuilder

Question 42

When to use StringBuilder.insert(int offset, data); ?

Answer 42

Useful when inserting a string at a specific position.

Question 43

This method replaces the characters between start and end indexes with the specified string.

Answer 43

replace(int start, int end, String str)

Question 44

The starting index (inclusive) where replacement

Answer 44

start

Question 45

The ending index (exclusive) where replacement stops.

Answer 45

end

Question 46

The new string that will replace the existing characters in the given range.

Answer 46

str

Question 47

The _______ method modifies the existing StringBuilder data without creating a new one.

Answer 47

replace()

Question 48

When to use replace(int start, int end, String str)?

Answer 48

useful when modifying a portion of the string.

Question 49

This method deletes characters between the specified start and end indexes.

Answer 49

delete(int start, int end)

Question 50

When to use delete(int start, int end)?

Answer 50

when removing unwanted parts of the string.

Question 51

Removes a single character at the specified index.

Answer 51

deleteCharAt(int index)

Question 52

The ________ method ______ the existing __________ instead of creating a new one.

Answer 52

deleteCharAt() , modifies, StringBuilder

Question 53

When to use deleteCharAt(int index)?

Answer 53

Useful for deleting a single character without affecting the rest of the string.

Question 54

This method reverses the sequence of characters in the StringBuilder.

Answer 54

reverse()

Question 55

This method modifies the existing StringBuilder in place.

Answer 55

reverse()

Question 56

When to use reverse()

Answer 56

useful when reversing strings for palindromes or algorithmic processing.

Question 57

This method returns the current capacity (storage size) of the StringBuilder.

Answer 57

capacity()

Question 58

__________ refers to the number of characters the StringBuilder can hold before it needs to resize.

Answer 58

Capacity

Question 59

Default capacity is ________ if created with new StringBuilder().

Answer 59

16 characters

Question 60

When the capacity is _________, it _________ using the formula:

Answer 60

exceeded, expands automatically

Question 61

What is the formula of Capacity method?

Answer 61

New Capacity = (Old Capacity * 2) + 2

Question 62

When to use capacity?

Answer 62

When understanding how much space is allocated before resizing occurs.

Question 63

This method does not shrink capacity, only increases it if necessary.

Answer 63

ensureCapacity(int minCapacity)

Question 64

This method ensures that the StringBuilder has at least minCapacity of storage, growing if necessary.

Answer 64

ensureCapacity(int minCapacity)

Question 65

If minCapacity is greater than the current capacity, the capacity increases using the formula. Which is ?

Answer 65

New Capacity = (Old Capacity * 2) + 2

Question 66

If minCapacity is less than or equal to the current capacity, what happens?

Answer 66

no change is made

Question 67

When to use ensureCapacity(int minCapacity)?

Answer 67

when preventing frequent resizing when adding large amounts of data.

Question 68

This method returns the number of characters in the StringBuilder.

Answer 68

length()

Question 69

What is the syntax of length?

Answer 69

int currentLength = StringBuilder.length();

Question 70

What differs lengths() to capacity()?

Answer 70

length() → Returns the actual number of characters in the StringBuilder. capacity() → Returns the total allocated space for characters.

Question 71

When to use length()?

Answer 71

When determining the current size of the content.

Question 72

This method returns the character at the specified index

Answer 72

charAt(int index)

Question 73

The position of the character to retrieve

Answer 73

index

Question 74

When to use charAt(int index)

Answer 74

When retrieving a specific character from the StringBuilder

Question 75

This method changes the character at the specified index to the given char c.

Answer 75

setCharAt(int index, char c)

Question 76

When to use setCharAt(int index, char c)?

Answer 76

Useful for modifying individual characters without modifying the whole string.

Question 77

This method returns a new String starting from start index to the end.

Answer 77

substring(int start)

Question 78

When to use substring(int start)

Answer 78

Extracts a portion of the StringBuilder as a String.

Question 79

This method extracts a portion of the string between the given start (inclusive) and end (exclusive) indexes.

Answer 79

substring(int start, int end)

Question 80

When to use substring(int start, int end)?

Answer 80

Extracts a portion of the StringBuilder as a String.

Question 81

This method converts the StringBuilder data into a String.

Answer 81

toString()

Question 82

When to use toString()?

Answer 82

Since StringBuilder is mutable, this method is used when we need an immutable String representation.

Question 83

What are the key differences of StringBuilder and StringBuffer?

Answer 83

the key difference is that StringBuffer is thread- safe (synchronized) but slower, while StringBuilder is faster but not thread-safe.

Question 84

What is the execution time for StringBuilder and StringBuffer when performing a large number of operations?

Answer 84

Appending 100,000 times

Question 85

Give 3 string types in Java

Answer 85

String (Immutable) StringBuffer (Mutable & Thread-Safe) StringBuilder (Mutable & Fast but Not Thread-Safe)

Question 86

"Since String is immutable, converting it to StringBuffer or StringBuilder allows modifications.". What type of conversion is this?

Answer 86

Convert String to StringBuffer and StringBuilder

Question 87

"Since StringBuffer and StringBuilder are mutable, converting them to String gives an immutable version." What type of conversion is this?

Answer 87

Convert StringBuffer and StringBuilder to String

Question 88

"Since both are mutable, Java doesn’t provide a direct method to convert between them. We first convert to String, then create a new instance of the other type." What type of conversion is this?

Answer 88

Convert StringBuffer to StringBuilder or Vice Versa

Question 89

In Java, working with different string types—_____, _____, and _______—is important for handling text efficiently.

Answer 89

String, StringBuffer, StringBuilder

Question 90

_________ is immutable, meaning it cannot be changed once created, while ______ and ______ are mutable, allowing _______ without creating ________.

Answer 90

String, StringBuffer, StringBuilder, modifications, new instance.

Question 91

The key difference between StringBuffer and StringBuilder is that StringBuffer is _________, making it suitable for _________, whereas StringBuilder is faster but not _________, making it ideal for ____________ environments.

Answer 91

thread-safe (synchronized), multi-threaded applications, synchronized, single-threaded