Programming Basics

Question 1

How to output “ Hello World “ in CMD using Java?

Answer 1

public class Filename >1
{ >2
public static void main ( String[]args ) >3
{ >4
System.out.println(“Hello World”); >5
} >6
} >7

Question 2

What does the world public mean in the first line of Java ?

Answer 2

• A keyword of Java language that indicates that the element that follows should be made available to other Java elements.
• Other class can also use it

Question 3

What does the curly brackets ( {} ) do in 2nd line and the last line?

Answer 3

• Everything that are included in the curly brackets belongs to the class

Question 4

What does the word void mean ?

Answer 4

• To indicate that no value is returned
• To let the program just run the program and return nothing

Question 5

What does static mean ?

Answer 5

• To run the method without calling on the class

Question 6

What does String [] args mean ?

Answer 6

• It is a parameter list

Question 7

Why it was not advisable to create identifiers using the Java Keywords

Answer 7

• May lead to confusion

Question 8

What is Java most concerned about ?

Answer 8

Case Sensitive
- for to For , it will be printing error

Question 9

The most important programming tips

Answer 9

1. Remember to semicolon ( ; )
2. Remember to check if there is any word that are being written in Uppercase Letters

Question 10

Java Keywords also known as

Answer 10

Reserved words

Question 11

Statements format ( 5 )

Answer 11

1.Declaration Statement
- int i ;
- String name ;

2. Assignment Statement
   
   • i = 42 ;
   • name = “ ADI “
3. Declaration + Assignment
   
   • int i = 42
   • String name = “ ADI “
4. Expression Statement
   
   • System.out.println(“Hello World”)
5. Many other more
   
   • for
   • if

Question 12

Statement must type semicolon ( ; ) after finishing

Answer 12

1. Declaration
2. Expression

Question 13

How can you create a block ?

Answer 13

1. Using brace { }

Question 14

Do we need to add semicolon after creating a block ?

Answer 14

No

Question 15

Which is correct?
1. int Total
= 100;
2. int Total = 100;

Answer 15

Both are correct

Question 16

What are double and float different ?

Answer 16

1. double - to represent double-precision 64-bit floating-point numbers
2. float - To represent single-precision 32-bit floating-point numbers

Question 17

How to create a comment?

Answer 17

1. Type // ( End-of-line Comments )
2. Type /* */ ( Traditional Comments )
3. ( Java DOC Comment )

Question 18

All identifiers must begin with what?

Answer 18

Letter ( a , d , A)

Question 19

What are the differences of state and behavior in Java?

Answer 19

1. Consist data that the object might be keeping track of.
2. Consists actions that the object can perform.

Question 20

Key Principles of OOP

Answer 20

1. Encapsulation
   - Encapsulation is the bundling of data (attributes) and methods (functions) that operate on the data into a single unit, known as a class.
2. Abstraction
   - Abstraction involves simplifying complex systems by modeling classes based on the essential properties and behaviors they share.
3. Inheritance
   - Inheritance is a mechanism that allows a new class (subclass or derived class) to inherit the properties and behaviors of an existing class (superclass or base class).
4. Polymorphism
   - Polymorphism allows objects of different classes to be treated as objects of a common superclass.

( PIEA )

Question 21

What are usually used for variable names in Java ?

Answer 21

Camel case ( myClass1Object )

Question 22

How to create another class

Answer 22

1. Create a new class in a different file
2. Then in the main file type :
   Greater ( Another class file name ) myGreeterObject ( Hold the objects in the Greeter file ) = new Greeter(); ( Create new objects )

Question 23

Variable must start with what first?

Answer 23

1. Letter ( m,k,l ,small letter first [ camel case ] )
2. Underscore ( _ )
3. Dollar Sign ( $ )

Question 24

What are class variable also known as?

Answer 24

Static Variables

Question 25

What are the rules that the static variables follow?

Answer 25

1. Must place within the class but not in the method ( Start of the code or the End ) 2. Must include the word static ( static int newNum = 5 )

Question 26

What is a static variables ?

Answer 26

Variable that can be shared among the class

Question 27

What is the usage of instance variables ?

Answer 27

To create us own class

Question 28

All Variable

Answer 28

1. Static Variable ( Outside of the method ) 2. Instance Variable ( Outside of the method ) 3. Local Variable ( Inside of the method ) 4. Final Variable ( Outside / Inside of the method )

Question 29

What are the difference about Static and Local Variable?

Answer 29

1. Static can put Above or Below the code 2. Local must put Above the code

Question 30

What is a Final Variable ?

Answer 30

The value can't change after being initialized

Question 31

How to add a Final Variable ?

Answer 31

Add a final word ( final int radius = 3.1415 )

Question 32

Which variables a given default values ?

Answer 32

1. Static Variable 2. Instance Variable

Question 33

All integer types

Answer 33

1. byte ( -128 to 127 ) 2. short ( -32,768 to 32,767 ) 3. int ( -2,000,000,000 to 2,000,000,000 ) 4. long ( -9,000,000,000,000 to 9,000,000,000,000 )

Question 34

Why there are so many integer types?

Answer 34

To save up some memory

Question 35

How to make values easier to read ?

Answer 35

Putting underscore ( 58_473_882 )

Question 36

All Floating-point types

Answer 36

1. float ( F at the back ) 2. double ( D at the back )

Question 37

All Character types

Answer 37

1. char ( Uses ' ' ) 2. String ( Uses " ")

Question 38

What does var do in Java ?

Answer 38

1. Decide the value is what type of data by itself

Question 39

Why is string is written in Uppercase Letters ( String ) than other variable ( int , boolean )?

Answer 39

Because string isn't primitive types, it was a reference types and it was the name provided by the Java API class

Question 40

How to combine two strings?

Answer 40

Adding a + sign

Question 41

How to convert an integer to string ?

Answer 41

Use the code Integer.toString() ( String s = Integer.toString (x); )

Question 42

How to convert a string to primitives value ?

Answer 42

1. int x = Integer.parseInt ( " 100 " ) 2. short x = Short.parseShort ( " 100 " ) 3. double x = Double.parseDouble ( " 19.01 " ) 4. boolean x = Boolean.parseBoolean ( " true " )

Question 43

What are convert numeric data of one type to another called ? ( int to double )

Answer 43

1. Casting

Question 44

How to input data using JOptionPane?

Answer 44

String priceDialog; priceDialog = JOptionPane.showInputDialog("Please enter the price of the goods : "); double goodsPrice = Double.parseDouble(priceDialog);

Question 45

How to input data from Terminal?

Answer 45

static Scanner sc = new Scanner(System.in) System.out.print("Please enter the price of the goods : "); double goodsPrice = sc.nextDouble();