java

How to create a new String object in Java?

• a) new String();

• b) String.new();

• c) String{};

• d) new Object(String);

Answer explanation

Explanation:

The new String(); syntax is used to create a new String object in Java.

2. What is the output of “Java” == “Java” in Java?

• a) true

• b) false

• c) Compilation error

• d) Runtime error

Answer explanation

Explanation:

Both string literals point to the same object in the string pool, so == will return true.

3. What does the charAt() method do?

• a) Returns the character at a specific index

• b) Changes the character at a specific index

• c) Removes the character at a specific index

• d) None of the above

Answer explanation

Explanation:

The charAt(int index) method returns the character at the specified index in the string.

What is the result of statement: String str = null;?

• a) Creates a new String with no characters

• b) Creates a String pointing to “null”

• c) Does not create any String

• d) Creates an empty String

Answer explanation

Explanation:

Declaring a String variable as null means it does not point to any memory location for an object.

5.Which method removes whitespace from the beginning and end of a string?

• a) trim()

• b) strip()

• c) clean()

• d) chop()

Answer explanation

Explanation:

The trim() method removes whitespace from both the beginning and the end of the string.

6.Is the String class in Java thread-safe?

• a) Yes

• b) No

• c) Only when synchronized

• d) Depends on the method being called

Answer explanation

Explanation:

Strings in Java are immutable, which means once a String object is created, its value cannot be modified. This inherent immutability makes them thread-safe, as multiple threads cannot change their value simultaneously.

7.What is the String Constant Pool in Java?

• a) A pool where all string methods are stored

• b) A special area of the heap memory where string literals are stored and reused

• c) A memory space where string objects are stored temporarily

• d) A section of the Java library dedicated to string operations

Answer explanation

The String Constant Pool is a specific area in the heap memory where Java stores string literals. The primary purpose of this is to save memory by reusing existing strings.

8.Which keyword in Java is used for constant variables?

• a) const

• b) static

• c) constant

• d) final

Answer explanation

In Java, the final keyword is used to declare constant variables.

9.What happens when you assign a new value to an existing variable in Java?

• a) The variable gets duplicated

• b) An error occurs

• c) The original value is overwritten

• d) The variable becomes undefined

Answer explanation

When a new value is assigned to an existing variable in Java, the original value is overwritten with the new one.

10.What is an object in Java?

• a) A reference to a class

• b) A runtime entity

• c) A method

• d) An attribute

Answer explanation

An object is a runtime entity, or in other words, a real-world entity, which is created based on a class.