Java Programming Fundamentals

• Unit: CIS096-1: Principles of Programming and Data Structure, CISO16-1: Principles of Programming

Variables

• A variable in Java is a container holding values that can be changed
• A correct way to declare a variable in Java is int x; or float x;
• The default integer variable value in Java is 0
• To declare a constant variable in Java, the keyword "final" is utilized
• The scope of a local variable in Java is within the block it is declared
• A float data type can store a decimal number in Java
• The correct method to initialize a double-type variable 'a' to 9.8 in Java is double a = 9.8d;
• The variable name "2myVar" is invalid in Java
• The keyword used for a variable that should not be serialized in Java is transient
• The type inference variable in Java, introduced in Java 10, is var
• String is not a primitive data type in Java
• Attempting to assign a float value to a long-type variable without explicit casting will result in Compilation error
• Static variables in Java are shared among all instances of a class
• Valid values for a Java byte variable ranges from -128 to 127
• A valid declaration of a char variable in Java is char myChar = 'A'; or char myChar = 65;
• If a variable is declared inside a for-loop in Java, It is only accessible within the for-loop
• The keyword used to define a variable with same value for every class instance is static final
• To declare a variable holding a number larger than 2 billion in Java, use long
• The default value of boolean variable in Java is false
• A valid declaration and initialization of an array in Java is int[] myArray = {1, 2, 3}; or int myArray[] = new int[]{1, 2, 3};

Methods

• A function in Java is a code block designed to perform a task
• You can define a method in Java by: datatype methodName(parameters)
• The keyword to define a method not returning any value is void
• Method overloading in Java involves creating multiple methods of the same name but with differing parameters
• A method in Java can return multiple values by using arrays or objects
• A valid method signature in Java is public double myMethod(int a, float b)
• To call a static method named "calculate" from a "MathOperations" class you use MathOperations.calculate();
• The this keyword in a method refers to the current class instance
• The access modifier allowing access from any Java class is public
• Final methods cannot be overridden by subclasses
• A constructor in Java initializes an object
• A 'void' return type means the method will not return any value
• Java does not directly support optional parameters
• Recursion in Java involves a method that calls itself
• Method overriding in Java are achieved by creating methods with same signatures in a subclass and parent class
• The return type of method not returning a value is void
• Method overloading requires a difference in number or the type of parameters
• The @Override annotation indicates a method overrides from a superclass
• Constructors cannot be overridden in Java
• A valid variable arguments (varargs) method declaration in Java is public void myMethod(int... numbers)

Conditional Statements

• The basic form of a conditional statement in Java is if (condition) { // statements }
• else if (condition) { // statements } adds an alternative condition to an if statement
• The operator ?: is used for simple conditional (ternary) operations
• String values are supported as of Java SE 7 and newer versions of switch statements
• Given x = 5; in the code, If (x > 3) {System.out.println("Apple");} else {System.out.println("Banana");} System.out.println("Cherry"); the output will be Apple Cherry
• if (1 < 2; 2 < 3) { // statements } is not a valid way to use an if statement in Java
• Omitting a break statement enables multiple switch statement cases to share the same code block
• Char grade, when executed with an if statement will output Well Done if case is assigned 'C'

Switch (grade) {
	case 'A':
		System.out.println(“Excellent”);
		break;
	Case ‘B’:
	Case ‘C’:
		System.out.println(“Well Done”);
		Break;
}

• The expression expr1 is executed, if the conditional statement is true in a ternary operator
• if (x > y) System.out.println("X"); else System.out.println("Y"); is the correct if-else statement format in Java
• Each else if condition must be mutually exclusive for an else if ladder to work correctly
• The default case in a switch statement catches any case not explicitly handled
• A 'switchstatement can refactor anif-else` chain checking equality for the same variable in multiple values
• Without a break statement in the swtich statement, subsequent cases will be executed until reaching the break statement.
• if (condition1 && condition2) { // statements } is the correct syntax for multiple conditions in an if statement.

Loops

• A loop's purpose in Java is to repeatedly execute a block of statements
• It is used to iterate a known number of times in a block of code in for loops
• A while loop has correct syntax of While (condition) {// statements} format.
• A 'do-while` loop terminates by ensuring the loop condition eventually evaluates to false
• The loop to use when the iteration count is unknown is the while loop
• The loop terminates code block with the use of a 'break' statement
• By using the 'continue' statement you can skip to the next iteration of the loop, skipping all other code
• for (int i=0; i<10; i++) { } is a declaration for a valid for loop within Java
• The condition is checked for in each iteration with the use of a 'do-while' loop
• A loop control statement to be aware of is the 'exit statement'
• A for loop that starts at 0 increments by 2 each time, up to 10 with statement: for (int i = 0; i <= 10; i += 2)
• Enhanced for loop for collections/arrays.
• The effect of a continue will skip and proceed to next iteration within a loop statement
• The initialization statement in a loop initializes the loop control variable
• With the code statement for (int i = 0; i < arr.length(); i++) { } you can loop the array 'arr'

Classes and Objects

• A class in Java is a template for creating objects
• An object in Java is an instance of a class
• ClassName objectName = new ClassName(); is how an class name is created to create the specific object name
• Use extends for inheritance
• Encapsulation is wrapping code and data as single unit
• An object has it's code that can be displayed as statement such as with objectName.methodName()
• 'This' is used to see current instance a user to see the current instance of a class.
• A constructor is defined with A method that has the class with no return type.
• Polymorphism is a program to perform on different method, with object being acted upon
• You cannot instantiate, class object is what abstract means to the Java software
• Using 'private modifier' you can access the modifier only with in class object
• if call toString method on object it will be B)Name of class "@" and followed by Java
• Not supported : Java does not allow multiple inherited method at the same time and is what the statement means.
• Method Overloading is that B) is not Valid (Method overloading and what is displayed in

Arrays, ArrayList and LinkedList

• The length parameter shows how much the numbers are elements
• ArrayList is ArrayList al = new ArrayList(); to show the elements in the code
• Add () in the statement is the way we add the al object
• al.remove(2) is how we can the parameters in code _Al.remove(2); is what displays how to add Al Return current list list elements
• ArrayList shows safety with arraylist
• Constant, allows you to make constant statements
• peek and get method is to retrieve the first item
• LinkedLists used LinkedList data elements

This lesson covers fundamental concepts of variables in Java, including declaration, initialization, and scope. It explores data types, constants, and type inference. Additionally, it explains the use of transient and static variables.