Conditional Statements

• These notes cover conditional statements in programming, including "if", "if-else", "if-else if", nested "if", shorthand "if, and "switch" statements.
• Conditional statements allow programs to make decisions based on conditions.
• Decisions are made based on whether a provided condition is true or false.
• "If" statements are constructs that enable a program to specify alternative paths of execution.

Types of Conditional Statements

• If Statement: Executes a block of code if a condition is true; based on a single condition.
• If-Else Statement: If a condition is 'true', one block of code executes, otherwise another block executes; based on 2 conditions.
• If-Else-If Statement: is based on multiple conditions
• Nested If Statements: Uses "if" statements inside of other "if" statements.
• Switch Statement: Provides an alternative to "if-else if" by allowing a variable to be tested against a list of values (cases).
• Ternary Operator: A shorthand "if-else" statement (? :).
• Short-Circuit Evaluation: Affects "&&" and "||" operators; stop evaluating once the outcome is determined.

If-Else Statement Details

• The if statement tests the boolean condition: 'true' or 'false'.
• In Java, the common types of "if" statements are: "if", "if-else", "if-else-if ladder", and "nested if" statement.

One Condition: If Statement

• The Java "if" statement executes the if block if the condition is true.
• Common syntax:

if(condition){
    //code to be executed
}

• Example:

if (you pass) { I will buy you a gift. }

Two Conditions: If-Else Statement

• The "if-else" statement tests the condition and executes the if block if the condition is true; otherwise, the else block is executed.
• Common syntax:

if(condition){
//code if condition is true
}else{
//code if condition is false
}

• Example:

If (you pass) { I will buy you a gift. }
else { you buy me a gift. }

Multi-Conditions: If-Else-If Ladder Statement

• Common syntax:

if(condition1){
//code to be executed if condition1 is true
}else if(condition2){
//code to be executed if condition2 is true
}
else if(condition3){
//code to be executed if condition3 is true
}
…
else{
//code to be executed if all the conditions are false
}

Nested If Statement

• represents the if block within another if block.
• Common syntax:

if(condition){
//code to be executed
        if(condition){
        //code to be executed
        }
}

Switch Statement

• Allows a variable to be tested for equality against a list of values.
• Each value in switch is called a case.
• Common syntax:

switch(expression){
case value1:
//code to be executed;
break; //optional
case value2:
//code to be executed;
break; //optional
…...
default:
code to be executed if all cases are not matched;
}

Optional One-Line Block

• If there are no curly braces to define any block, the "if" statement only takes on the statement on its line as its block statement.

Simplify Code

• The equivalent code using a "boolean" is better than the "if-else" statement

Lab Tasks

• Simple If Condition: Write a program that checks if a number is positive; if so, provide output.
  • Input: 5 -> Output: "Number is positive"
  • Input: -3 -> No output
• If-Else Statement: Write a program that checks if a student has passed or failed (pass mark = 50).
  • Input: 75 -> Output: "You passed!"
  • Input: 30 -> Output: "You failed!"
• Nested If Statements: Write a program that checks if a number is positive, negative, or zero.
  • Input: 5 -> Output: "Positive number"
  • Input: -3 -> Output: "Negative number"
  • Input: 0 -> Output: "Zero"
• If-Else If-Else Statement: Write a program that assigns grades based on a student's score.
  • 90+ -> "A"
  • 80-89 -> "B"
  • 70-79 -> "C"
  • 60-69 -> "D"
  • <60 -> "F"
• Switch Case Statement: Write a program that takes a day number (1-7) and prints the corresponding weekday.
  • Input: 1 -> Output: "Monday"
  • Input: 7 -> Output: "Sunday"
• Ternary Operator: Write a program that determines if a number is even or odd using a ternary operator.
  • Input: 4 -> Output: "Even"
  • Input: 7 -> Output: "Odd"
• Checking Leap Year (Nested If & Logical Operators): Create a program to check if a given year is a leap year.
  • Input: 2024 -> Output: "Leap year"
  • Input: 2023 -> Output: "Not a leap year"
• Largest of Three Numbers (Nested If or Ternary Operator): Create a program that finds the largest of three numbers.
  • Input: 5, 10, 3 -> Output: "10 is the largest"
• Age Verification (If-Else): Create a program that checks if a person is eligible to vote (age >= 18).
  • Input: 20 -> Output: "Eligible to vote"
  • Input: 16 -> Output: "Not eligible to vote"
• Traffic Light Simulation (Switch Case): Create a program that takes a traffic light color (red, yellow, green) as input and prints the corresponding action.
  • Input: "red" -> Output: "Stop"
  • Input: "green" -> Output: "Go"