lec 2

Question 1

How do you print a variable in Java?

Answer 1

System.out.println(variableName);

Question 2

How do you concatenate a variable with text in System.out.println()?

Answer 2

Use +, e.g., System.out.println(“Age: “ + age);

Question 3

What happens when + is used between two numbers?

Answer 3

It performs addition.

Question 4

What happens when + is used between a string and a number?

Answer 4

It concatenates them into a string.

Question 5

How do you declare a constant variable?

Answer 5

Use the final keyword, e.g., final double PI = 3.14159;

Question 6

What happens if you try to reassign a value to a final variable?

Answer 6

It causes a compilation error.

Question 7

What are Java identifiers?

Answer 7

Names used for variables, methods, classes, etc.

Question 8

What are the rules for naming identifiers?

Answer 8

They must start with a letter, _, or $, and cannot be a reserved word

Question 9

How should Java constants be named?

Answer 9

Using uppercase letters with underscores, e.g., MAX_VALUE.

Question 10

What must every Java program be contained within?

Answer 10

A class.

Question 11

What is the naming rule for Java files?

Answer 11

The Java file name must match the class name and end with “.java”.

Question 12

What is the purpose of System.out.println();?

Answer 12

It prints a line of text to the screen.

Question 13

What must every Java statement end with?

Answer 13

A semicolon (;).

Question 14

How does Java treat case sensitivity?

Answer 14

Java is case-sensitive; MyClass and myclass are different.

Question 15

What is the purpose of the main() method in Java?

Answer 15

It serves as the entry point for execution.

Question 16

What is the syntax for the main() method?

Answer 16

public static void main(String[] args)

Question 17

What are the two types of comments in Java?

Answer 17

Single-line (//) and multi-line (/* … */).

Question 18

How do you write a single-line comment?

Answer 18

Use // before the comment.

Question 19

How do you write a multi-line comment?

Answer 19

Use /* … */ to enclose multiple lines of comments.

Question 20

What are variables in Java?

Answer 20

Containers for storing data values.

Question 21

Name the five main variable types in Java.

Answer 21

String, int, float, char, and boolean.

Question 22

What data type would you use to store a whole number?

Answer 22

int.

Question 23

What data type would you use to store a decimal number?

Answer 23

float or double.

Question 24

What data type would you use to store a single character?

Answer 24

char.

Question 25

What data type would you use to store true or false?

Answer 25

boolean.

Question 26

How do you declare an integer variable?

Answer 26

int x;

Question 27

How do you assign a value to a variable?

Answer 27

x = 10;

Question 28

How do you declare and assign a variable in one step?

Answer 28

int x = 10;

Question 29

What happens if you assign a new value to an existing variable?

Answer 29

It overwrites the previous value.

Question 30

What is the syntax for declaring multiple variables in one line?

Answer 30

int x = 5, y = 6, z = 10;

Question 31

What is the correct way to declare a floating-point variable in Java?

Answer 31

float x = 10.5f;

Question 32

Which of the following is a valid Java identifier?

Answer 32

helloWorld123