Java Data Types and String Manipulation

What are the four main primitive data types in Java?

• char, int, long, object

• int, boolean, char, double

• int, float, boolean, string

• float, string, byte, short

How do you declare a variable in Java?

• variableName dataType;

• dataType: variableName;

• var variableName;

• dataType variableName;

What is the default value of a boolean variable in Java?

• true

• false

• null

• 1

Explain the difference between 'int' and 'Integer' in Java.

• 'int' can hold null values; 'Integer' cannot.

• 'int' is a reference type; 'Integer' is a primitive type.

• Both 'int' and 'Integer' are the same and interchangeable.

• 'int' is a primitive type; 'Integer' is a wrapper class.

What is the purpose of the 'final' keyword when declaring a variable?

• The 'final' keyword is used to declare a variable that can hold multiple data types.

• The 'final' keyword allows a variable to be reassigned multiple times.

• The 'final' keyword makes a variable accessible only within its own method.

• The 'final' keyword makes a variable immutable, preventing it from being reassigned after its initial assignment.

What is the output of the following code: int x = 5; System.out.println(x++);?

• 4

• 6

• 5

• 5.0

What is the scope of a variable declared inside a method?

• Static scope limited to the class.

• Local scope within the method only.

• Global scope accessible throughout the program.

• Block scope only within the nearest curly braces.

How do you concatenate two strings in Java?

• You must use the String.join() method to concatenate strings.

• Strings can only be concatenated using the StringBuilder class.

• You can concatenate two strings in Java using the '+' operator or the String.concat() method.

• You can concatenate two strings using the '&' operator.

What method would you use to find the length of a string in Java?

• Use the size() method of the String class.

• Call the getLength() function on the String object.

• Use the count() method of the String class.

• Use the length() method of the String class.

What is the difference between '==' and '.equals()' when comparing strings?

• Both '==' and '.equals()' are interchangeable for string comparison.

• The '==' operator checks reference equality, while '.equals()' checks value equality.

• '.equals()' checks reference equality only.

• '==' checks both reference and value equality.